EP1437459A1 - Reinforcement material and reinforcement structure of structure and method of designing reinforcement material - Google Patents
Reinforcement material and reinforcement structure of structure and method of designing reinforcement material Download PDFInfo
- Publication number
- EP1437459A1 EP1437459A1 EP02775228A EP02775228A EP1437459A1 EP 1437459 A1 EP1437459 A1 EP 1437459A1 EP 02775228 A EP02775228 A EP 02775228A EP 02775228 A EP02775228 A EP 02775228A EP 1437459 A1 EP1437459 A1 EP 1437459A1
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- European Patent Office
- Prior art keywords
- reinforcing member
- range
- reinforcement
- reinforcing
- young
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/01—Reinforcing elements of metal, e.g. with non-structural coatings
- E04C5/02—Reinforcing elements of metal, e.g. with non-structural coatings of low bending resistance
- E04C5/04—Mats
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/07—Reinforcing elements of material other than metal, e.g. of glass, of plastics, or not exclusively made of metal
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
- E04G23/0225—Increasing or restoring the load-bearing capacity of building construction elements of circular building elements, e.g. by circular bracing
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
- E04G2023/0251—Increasing or restoring the load-bearing capacity of building construction elements by using fiber reinforced plastic elements
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G23/00—Working measures on existing buildings
- E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging
- E04G23/0218—Increasing or restoring the load-bearing capacity of building construction elements
- E04G2023/0251—Increasing or restoring the load-bearing capacity of building construction elements by using fiber reinforced plastic elements
- E04G2023/0255—Increasing or restoring the load-bearing capacity of building construction elements by using fiber reinforced plastic elements whereby the fiber reinforced plastic elements are stressed
Definitions
- the present invention relates to a reinforcing member for a structural body, a reinforced structure using the reinforcing member, and a method for designing the reinforcing member.
- a conventional technique characterized by installing a reinforcing member on the surface of or inside a structure member subject to reinforcement includes (1) a technique of embedding a reinforcing bar in concrete as a substrate, or so-called reinforced concrete technique, (2) a technique of driving a bolt or nail into a substrate, (3) a technique of incorporating a high-strength steel rod inside concrete as a substrate and introducing a tensile force to the steel rod, (4) a technique of wrapping a steel plate around a structure member, or so-called steel-plate wrapping technique, and (5) a technique of using a so-called continuous-fiber reinforcing member made of carbon or aramid fibers and resin, such as epoxy resin, impregnated therein.
- Another conventional technique characterized by installing a reinforcing member between the respective outer surfaces of adjacent structure members includes (6) a technique of forming a space, such as hole or slit, in the structure members, and penetratingly inserting a reinforcing member into the space, and (7) a technique of forming a space in the structure members, penetratingly inserting bundled fibers of a continuous-fiber reinforcing member into the space, and then spreading out the fibers.
- Still another conventional technique characterized by installing a reinforcing member on the surface of a flat structure member, such as wall includes (8) a technique of constraining a reinforcing member by a metal plate formed with a hole, and a bar, such as a metal bar, penetrating the structure member, and (9) a technique of bundling the fibers of a continuous-fiber reinforcing member at the edge of the structure member, and anchoring the bundled fibers to the edge of the structure member or another member adjacent to the structure member.
- Yet another conventional technique characterized by forming a reinforcing member in a cylindrical shape and filling the inner space of the cylindrical reinforcing member with filler includes (10) a technique of forming an iron reinforcing member in a cylindrical shape, and filling the inner space of the cylindrical reinforcing member with concrete to use the obtained reinforcing member as a column.
- Yet still another conventional technique characterized by installing a plurality of reinforcing members on the outer surface of a structure member in a superimposed manner includes (11) a technique of providing a plurality of continuous-fiber reinforcing members on the outer surface of a structure member in its vertical and horizontal directions in a superimposed manner.
- Another further conventional technique characterized by providing a strip-shaped reinforcing member on the outer surface of a structure member includes (12) a technique of providing a strip-shaped (tape-shaped) steel plate or continuous-fiber reinforcing member around a structure member, (13) a technique of filling epoxy resin along a crack of a substrate in a strip shape, and (14) a technique of fixing a strip-shaped steel plate on the surface of a structure member by use of epoxy resin or an anchor bolt.
- Still a further conventional technique characterized by installing a reinforcing member on the outer surface of a junction of structure members includes (15) a technique of providing a steel jacket or attaching a continuous-fiber reinforcing member on the outer surface of a junction of structure members.
- An additional conventional technique characterized by using a resin-impregnated reinforcing member includes (16) a technique of using a so-called continuous-fiber reinforcing member made of carbon or aramid fibers and epoxy resin impregnated therein.
- the above techniques (4) to (14) are intended to transmit a shear stress directly to a reinforcing member without causing any displacement or peeling between a substrate and the reinforcing member.
- the shear reinforcement effect of a reinforced concrete member is said to have the same mechanism as that of a shear-reinforcing bar, and the reinforced concrete member is designed by assigning a reinforcement amount and coefficients expressing the property and reinforcement effect of a reinforcing member to a design formula of the shear-reinforcing bar.
- Most of the techniques (3) and (15) also include the step of injecting a grouting or resin material between a reinforcing member and a substrate to transmit a shear stress directly to the reinforcing member.
- substrate herein means a material constituting a structure member, and a physical object to which a reinforcing member is to be fixed.
- the reinforcing member such as the reinforcing bar, the steel rod and the steel plate, used in the techniques (1) to (4), (6), (8), (10), (12), (14) and (15), has the flexural rigidity and shear rigidity of its own.
- the reinforcing member cannot follow the local strain, resulting in loss of the reinforcement effect due to the occurrence of local fracture in the substrate or local buckling or cracks in the reinforcing member.
- the reinforcing member made of resin-impregnated continuous fibers has the same problem as described above due to the flexural and shear rigidities resulting from the effect of resin impregnation in addition to the flexural and shear rigidities of the continuous fibers themselves. Further, while this reinforcing member is designed using a formula based on the assumption that it has only tensile rigidity, an intended reinforcement effect is actually likely to be lost due to occurrence of bending or local buckling in consequence of the flexural rigidity and shear rigidity of its own.
- the material such as carbon or aramid fibers, used in the techniques (5), (7), (11) and (16), has a fracture strain of 2% to several %, which is liable to cause damages by the comers of a substrate or the unevenness of the surface of a substrate. Thus, an appropriate construction management is essentially required. Further, if the substrate has some cracks due to a certain external force, the reinforcing member will be locally broken, which leads to significant deterioration or disappearance of the reinforcement effect.
- a plate, a rod or a bundle of continuous fibers which serves as an anchor portion of the reinforcing member has a structure and rigidity different from those of the remaining portion of the reinforcing member.
- anchor member has a structure and rigidity different from those of the remaining portion of the reinforcing member.
- the substrate is requited to bear the stress occurring at the fixed portion of the anchor member. Therefore, if the strength of the substrate is lowered due to aged deterioration or such an aged deterioration is calculated, the above technique cannot be applied.
- the techniques (1) to (16) are required to install the reinforcing member by spending an extended time in association with professional engineers, which involves a high construction cost.
- the application of these techniques is also limited to a specific substrate which can be formed to have a smooth surface as in reinforced concrete, and allows a reinforcing member to be brought into close contact therewith so as to form a structure capable of locally transmitting a shear force.
- the reinforcing member is fixed through the many steps as described above, and the adhesive in the step (v) can be applied only after the adhesive applied in the step (iii) is completely cured or hardened by chemical action (if the adhesive in the step (v) is prematurely applied, gas bubbles generated during the chemical action will be confined in the reinforcing member to cause the deterioration in strength of the reinforcing member.
- the above process has to be completed by taking a great number of days.
- the impregnating step has to be carried out in the working site under a strict construction management. If an external force acts to cause the peeling between the resin and the continuous fibers, or the resin is defective in curing or deteriorated due to environmental conditions, the design performance of the reinforcing member will be significantly degraded.
- a structure member has a non-flat or irregular surface, such as a wall-mounted column, or is joined to or located very close to another member or non-structural material, such as a column having a window frame attached thereto, it is difficult to obtain a sufficient reinforcement effect. Further, the interactions between a structure member and a reinforcing member and between the reinforcing member and the surrounding are likely to cause deterioration of the reinforcing member. Furthermore, there is the need for obtaining a sufficient reinforcement effect in a wide range from a small deformation to a large deformation.
- a reinforcing member comprising a woven body formed by a weaving process to have a high ductility and high bendability.
- the reinforcing member is adapted to be installed on a surface of or inside a structure member to reinforce the structure member.
- the woven body has a Young's modulus equal to or less than that of the structure member, and a tensile fracture strain of 10% or more.
- the Young's modulus of the woven body may be in the range of 1/2 to 1/20, preferably 1/5 to 1/10, of that of the structure member. Specifically, the Young's modulus of the woven body may be in the range of 500 to 50000 MPa, preferably 1000 to 10000 MPa.
- the woven body may have a thickness in the range of 0.2 to 20 mm, preferably 0.5 to 15 mm, more preferably 1 to 10 mm.
- the woven body may include yarns made of polyester.
- the woven body may have a bending deformation angle of 90-degree or more, and a shear deformation angle of 2-degree or more.
- the reinforcing member set forth in the first aspect of the present invention may be heat-set to allow a Young's modulus in a limit state to be greater than a Young's modulus immediately before fracture.
- the heat setting process comprises the steps of heating the reinforcing member to apply a tensile force thereto, and then cooling the reinforcing member while maintaining the tensile force, so as to provide enhanced initial rigidity and Young's modulus to the reinforcing member.
- a resin impregnation process may be performed to impregnate the reinforcing member with resin.
- This reinforcing member may have an elongation strain in the range of 0.1 % to 10% in the limit state.
- a reinforcing member comprising a tape-shaped or sheet-shaped body made of a rubber-based or resin-based elastic material having a high ductility and high bendability.
- the reinforcing member is adapted to be installed on a surface of or inside a structure member to reinforce the structure member.
- the tape-shaped or sheet-shaped body has a Young's modulus equal to or less than that of the structure member, and a tensile fracture strain of 10% or more.
- the Young's modulus of the tape-shaped or sheet-shaped body may be in the range of 1/2 to 1/20, preferably 1/5 to 1/10, of that of the structure member. Specifically, the Young's modulus of the tape-shaped or sheet-shaped body may be in the range of 500 to 50000 MPa, preferably 1000 to 10000 MPa.
- the tape-shaped or sheet-shaped body may have a thickness in the range of 0.2 to 20 mm, preferably 0.5 to 15 mm, more preferably 1 to 10 mm.
- the tape-shaped or sheet-shaped body may have a bending deformation angle of 90-degree or more, and a shear deformation angle of 2-degree or more.
- the reinforcing member set forth in the second aspect of the present invention may be formed by spraying or applying a rubber-based or resin-based material or fiber-reinforced mortar to the structure member in the working site. While the material cost in this case is higher than the polyester woven fabric, it is often the case that such a reinforcing member is advantageous in terms of the ratio of reinforcement effect to cost as compared to conventional techniques.
- a Young's modulus in a limit state such as a design ultimate state, a fracture strain and a fracture stress can be calculated based on the stress-strain relationship of the reinforcing member to determine a required reinforcement amount (the thickness of the reinforcing member) and the performance of the structure member according to an after-mentioned calculation method.
- the reinforced structures comprise the reinforcing members set forth in the first and second aspects of the present invention, respectively.
- the reinforcing member is fixed on a surface of or inside a substrate which constitutes a structure member of the structural body and consists of at least one material, or on a surface of a boundary portion of the structure member or inside the structure member, to reinforce the structure member.
- the reinforcing member may be fixed to the structure member in such a manner that an effective constraint range of the reinforcing member covers the pre-calculated width and length of a gap to be generated in the structure member in future.
- the substrate may be made of at least one material selected from the group consisting of (1) concrete, (2) steel frame, (3) brick, (4) block, (5) gypsum board or plaster board, (6) wood, (7) rock, (8) earth or soil, (9) sand, (10) resin and (11) metal.
- the fixation may be performed by means of an adhesive.
- the layer of the adhesive applied to the reinforcing member or the structure member may have a thickness in the range of 5 to 90%, preferably 20 to 40%, of the thickness of the reinforcing member.
- the fixation may be performed by placing the reinforcing member on the structure member through the layer of the adhesive and then applying a pressing force or a beating force to the reinforcing member while allowing a part of the adhesive to be infiltrated into the reinforcing member.
- the fixed portion of the reinforcing member may have a void ratio of 1.1 or more.
- the fixed portion of the reinforcing member may have a void ratio of 1.4 or more.
- the bonding strength of the fixation may be less than the peeling/shear fracture strength between the structure member and the reinforcing member. This prevents the reinforcement effect from disappearing due to fracture in the structure member and the reinforcing member before the occurrence of peeling in the fixed portion.
- the bonding strength may be in the range of 10 to 80% of peeling/shear fracture strength in the surface of the structure member applied with the adhesive.
- the adhesive may be a one-component, non-solvent adhesive.
- the fixation of the reinforcing member to the structure member may be performed without chamfering the structure member and adjusting the unevenness of the surface of the structure member.
- the reinforcing member holds or constrains the structure member in such a manner that it forms an envelope surface covering a surface of the structure member adjacent to the gap to serve as a medium for transmitting a stress acting on the structure member on both sides of the gap (bridge for transmitting the stress).
- the envelope surface serving as the transmission medium is formed by elongation in the reinforcing member adjacent to the gap and/or peeling in the fixed portion adjacent to the gap.
- the envelope surface serving as the transmission medium is formed by the elastic elongation of the reinforcing member in a free zone where the fixation is released due to the generation of the gap.
- substrate means a material constitutes a structure member subject to reinforcement, and a physical object to which a reinforcing member is to be fixed.
- the shape and material of the substrate are appropriately selected depending on a desired performance or function of the structure member.
- the material of the substrate is not limited to a specific form or type, and may be any conventional structural material, any conventional non-structural material or any filler material.
- the substrate may be concrete, steel frame, brick, block, gypsum or plaster board, precast concrete, wood, rock, earth or soil, sand, metal, or granular resin.
- the substrate may include plural kinds of materials. For example, when a filler material such as resin is filled in a space between a structure member and a reinforcing member, the combination of the filler material and the material of the structure member may be defined as the substrate.
- gap herein means a chap or crack generated in a structure member.
- a structure member has a deformation inducing a gap therein, the resulting displacement between the structure member and a reinforcing member adjacent to the gap forms an envelope surface in a portion of the reinforcing member around the gap of the structure member without any fracture of the reinforcing member.
- the enveloped surface serves as a bridge allowing a stress of the structure member to be transmitted across the gap. That is, a shear stress is transmitted through the boundary surface between the reinforcing member and a portion of the structure member having no gap or through a fixed portion.
- the envelope surface of the reinforcing member is formed based on a plurality of factors including as the elongation of the reinforcing member adjacent to the gap, the release (peeling or another factor) of the fixation adjacent to the gap, and the fixation around the gap.
- the fixation of a reinforcing member to a structure member is performed by applying an adhesive a part or all of the boundary surface between the structure member and the reinforcing member, or by closingly looping a reinforcing members in an adhesive or mechanical manner while enclosing and deforming a portion of the structure member, so as to provide a tensile force in the reinforcing members to generate a frictional or bearing force between the reinforcing member and the structure members.
- the adhesive to be applied to the boundary between a structure member and a reinforcing member is required to maintain an adhesion strength required for fixing the reinforcing member to the structure member, for the period of use of the structure member under environmental conditions of the structure member. In this case, there is no need to set the required adhesion strength at a value higher than the fracture strength of the structure member or the reinforcing member.
- the adhesive may be one-component adhesive.
- the adhesive may also be applied to the reinforcing member in advance, and stored together with the reinforcing member. In this case, an operation of fixing the reinforcing member can be quickly completed.
- fixation zone herein means a zone where the reinforcing member is fixed.
- free zone means a zone where the fixation of the reinforcing member is released (due to peeling or another factor).
- the ratio of the size of the fixation zone to the size of the free zone is expressed by a numerical value of "constraint ratio".
- fixation strength and “fixation range” herein mean a strength and a range capable of causing the displacement in a specific finite areas (free zone) of reinforcing and structure members when the structure member has a local fracture inducing a gap, so as to allow a stress of the structure member to be transmitted through the reinforcing member across the gap without any fracture of the reinforcing member.
- the relationship between load and deformation of the structure member after the generation of the gap is expressed as the functions of the dimensions of the structure member, the boundary condition of the structure member, the position and size of the gap, the Young's modulus and thickness of the reinforcing member, and the size of a free zone caused by the gap.
- a required strength, required Young's modulus, required amount (required installation range, required thickness etc.) and required fixation strength of the reinforcing member can be calculated based on a value in a limit state (tolerance or threshold value) of the size (width etc.) of a gap to be generated in the structure member, the size of a zone where the elongation of the reinforcing member can be neglected (fixation zone), and the size of a zone where the reinforcing member is to be elongated (free zone).
- a Young's modulus for use in the calculation of the required amount etc. of the reinforcing member is a value (limit state value) corresponding to a strain to be generated in the reinforcing member in a limit state where the size of the gap reaches the threshold value. Therefore, in view of the elastic property of the reinforcing member, the design of setting a Young's modulus in the limit state to be greater than a Young's modulus corresponding to another strain such as a strain immediately before fracture can advantageously reduce the reinforcement amount.
- the installation range of the reinforcing member is not necessarily the entire surface of the structure member, but may be a portion of the structure member.
- the reinforcing member is installed to form an envelope surface in the circumferential direction of the structure member or to form a surface capable of being in contact with the portion of the surface of the structure member smoothly from the outside.
- the installation range of the reinforcing member is selectively determined depending on a desired performance, shape or configuration of a structure member, or a method of fixing a reinforcing member. For example, if a plurality of structure members are located adjacent to each other, the reinforcing member may be installed such that an envelope surface is formed to cover the junction between the adjacent structure members, or it is penetratingly inserted into a hole or slit formed in the adjacent structure members. Further, if the structure member is a flat member such as a wall, a reinforcing member may be installed on only one of the opposite surfaces thereof, or a reinforcing member may be installed on the respective opposite surfaces thereof and closingly looped through a through-hole formed in the structure member.
- the aforementioned reinforced structure may be formed by providing a reinforcing member to a structure member of an existing structural body, or may be formed by installing a reinforcing member to a structure member of a structural body to be newly constructed.
- the size and weight of the structure member can be reduced as compared to the conventional techniques to provide reduced seismic load. This makes it possible to achieve drastically reduced construction cost of the structural body, and significantly enlarged utilizable space of a living room or the like.
- FIG. 1 is a perspective view of a structure member (or a member of a structural body) with a reinforcement member according to an embodiment of the present invention.
- FIG 2 is a sectional view taken along the line A-A in FIG. 1.
- a structure member 1 comprises a substrate 3 with a reinforcing member 5.
- the reinforcing member 5 is installed, for example, in such a manner that it envelops a portion of the surface of the substrate 3 (see FIG. 1), or it encloses a given portion (periphery etc.) of the substrate (FIG 3).
- the substrate 3 is principally a material constituting the structure member 1 subject to reinforcement, and a physical object to which the reinforcing member 5 is to be fixed.
- the shape and material of the substrate 3 are appropriately selected depending on a desired performance or function of the structure member 1.
- the substrate 3 is a structural material such as reinforced concrete, a non-structural material such as block or brick, or a filler material such as sand or granular resin.
- the reinforcing member 5 installed on the surface the substrate 3 acts to bear a stress of the substrate 3 while bridging between both sides of a fractured surface such as chap or crack (or gap) generated in the substrate.
- a reinforcing member 5 is composed of a woven body having all of extensibility (high ductility and high bendability), strength and elasticity, and adapted to be installed on the surface of or inside a substrate of a structural body to reinforce the substrate.
- the woven body characteristically has a Young's modulus equal to or less than that of the structure member (substrate), and a tensile fracture strain of 10% or more.
- the term "Young's modulus of the structure member (substrate)" herein means the lowest one in the respective Young's moduluses of the materials.
- the reinforcing member has high ductility and high bendability, or extensibility.
- high ductility means to have a large fracture strain.
- high bendability means to readily cause a large bending deformation and shear deformation (high flexibility) without fracture.
- the reinforcing member having high ductility can constrain the substrate without fracture to maintain a desired reinforcement effect.
- the reinforcing member having high bendability can be readily bent at an acute angle.
- the reinforcement can be installed along an irregular circumferential surface of a structure member, and can be deformed under load to have a fixed portion formed in conformity to the curvature or corner angle of a substrate.
- the reinforcing member is required to have elasticity for generating a tensile force in response to change in the circumferential length of a substrate to bring out a geometrical constraint effect and coping with a repeated alternate load or the like.
- the rigidity of the reinforcing member is greater at the initial stage of the generation of strain than immediately before fracture.
- the Young's modulus of the woven body constituting the reinforcing member 5 is set to be equal to or less that that of the structure member. This is intended to reduce a stress acting on the boundary surface the reinforcing member and the substrate 3 when the reinforcing member starts deforming in response to the occurrence of deformation or crack in the structure member 1 due to a load acting on the substrate 3, so as to increase a limit deformation causing peeling in the boundary surface. Further, the tensile fracture strain of the woven body is set at 10% or more. Because in the design of structural bodies for an accidental load due to earthquake or the like, a design limit is generally about 2 to 4% of deformation in a structure member.
- the reinforcing member would be not fractured in the design limit if the fracture strain is 10% or more.
- the fracture strain is 10% or more.
- the structure member was reinforced by a SRF reinforcing member having 10% or more of fracture strain, no fracture was observed in the reinforcing member
- the Young's modulus and fracture strain of aromatic polyamide fibers used therein are directly applicable.
- the Young's modulus is in the range of 80000 to 120000 MPa
- the tensile fracture strain is in the range of 2.5 to 4.5%.
- the aromatic polyamide fibers act as an actual reinforcing member, it will be an aromatic-polyamide-fiber-reinforced epoxy resin having higher bending and shear rigidities than those of the elemental fibers.
- the reinforcing member is likely to peel off over a wide range at the same time due to inability of following the deformation of a substrate.
- the Young's modulus of concrete is about 20000 MPa
- the Young's modulus of hard wood such as oak is about 10000 MPa.
- the Young's modulus of the woven body is preferably in the range of 1/2 to 1/20, more preferably 1/5 to 1/10, of that of the substrate. If the Young's modulus is less than the lower limit of the range (or the value of Young's modulus is excessively small), the reinforcing member has to be designed to have an increased thickness to obtain a desired reinforcement amount. This is economically inefficient. Further, as described later, a peeling-limit elongation ( ⁇ 1: FIGS. 44 and 45) is increased, resulting in delayed response of the reinforcement effect and increased damage of the structure member.
- the Young's modulus of the reinforcing member is preferably in the range of about 500 to 5000 MPa, more preferably about 1000 to 1000 MPa.
- the tensile fracture strength of the woven body is in the range of 3 to 5 times of that of the structure member. Any local fracture of the structure member can be avoided by setting a stress concentration coefficient in the range of 3 to 5.
- the thickness of the woven body is preferably in the range of 0.2 to 20 mm, more preferably 0.5 to 15 mm, particularly 1 to 10 mm. This range is desired to obtain an intended performance and facilitate handling.
- the material of strings constituting the woven body is polyester (fiber).
- the woven body has a bending deformation angle of 90-degree or more, and a shear deformation angle of 2-degree or more.
- the woven body is heat-set to allow a Young's modulus in a limit state to be greater than a Young's modulus immediately before fracture.
- the reinforcing member has an elongation strain in the range of 0.1% to 10% in the limit state.
- a reinforcing member is a tape-shape or sheet-shaped body made of a rubber-based or resin-based elastic material, and adapted to be installed on a surface of or inside a substrate of a structural body to reinforce the substrate. Further, the tape-shaped or sheet-shaped body has a Young's modulus equal to or less than that of the structure member, and a tensile fracture strain of 10% or more.
- the Young's modulus of the tape-shaped or sheet-shaped body is preferably in the range of 1/2 to 1/20, more preferably 1/5 to 1/10, of that of the substrate.
- the Young's modulus of the reinforcing member composed of the tape-shaped or sheet-shaped body is also preferably in the range of about 500 to 5000 MPa, more preferably about 1000 to 1000 MPa.
- the thickness of the tape-shaped or sheet-shaped body is preferably in the range of 0.2 to 20 mm, more preferably 0.5 to 15 mm, particularly 1 to 10 mm.
- the tape-shaped or sheet-shaped body has a bending deformation angle of 90-degree or more, and a shear deformation angle of 2-degree or more.
- Two types of reinforced structures for a structural body according to third and fourth modes embodiment of the present invention comprise the reinforcing members according to the first and second modes of embodiment, respectively. Further, the reinforcing member is fixed on a surface of or inside a substrate constituting a structure member and including at least one material to reinforce the substrate.
- the reinforcing member is preferably fixed to the substrate in such a manner that an effective constraint range of the reinforcing member covers the pre-calculated width and length of a gap to be generated in the substrate in future.
- the reinforcing member 5 is fixed to the substrate 3 in the structure member 1. More specifically, the reinforcing member 5 and the substrate 3 are constrained to one another.
- the mechanism of this constraint is roughly classified into two types. A first mechanism is a bonding constraint, and a second mechanism is a geometrical constraint.
- the first mechanism or bonding constraint is achieved by bonding the reinforcing member 5 to the substrate 3.
- the bonding constraint can be maintained.
- the thickness of the layer of an adhesive applied to the reinforcing member or the substrate is preferably in the range of 5 to 90%, more preferably 20 to 40%, of the thickness of the reinforcing member.
- the fixation is performed by placing the reinforcing member on the substrate through the layer of the adhesive and then applying a pressing force or a beating force to the reinforcing member while allowing a part of the adhesive to be infiltrated into the reinforcing member.
- the fixed portion of the reinforcing member preferably has a void ratio of 1.1 or more.
- the fixed portion of the reinforcing member preferably has a void ratio of 1.4 or more. In this way, gas generated during the curing reaction of the adhesive can be adequately released from the adhesive layer or the reinforcing member.
- an initial bonding ability can be achieved without generation of gas bubbles in the adhesive layer, defective bonding, and swollenness and float of the adhesive layer.
- the upper limit of the void ratio is not limited to a specific value, but preferably in the range of about 2 to 3.
- the bonding strength is less than the strength of the substrate. If the bonding strength is equal to or greater than the strength of the substrate, the fracture of the structure member causes the generation of a tensile force in the reinforcing member and the release of the bonding to annul the reinforcement effect in a wide range at the same time.
- the bonding strength is preferably in the range of 10 to 80% of peeling/shear fracture strength in the surface of the substrate applied with the adhesive. If the bonding strength is higher than the upper limit of the range, the structure member will be damaged in an operation of detaching the reinforcement. If the bonding strength is lower than the lower limit of the range, a desired reinforcement effect cannot be obtained.
- the bonding strength is preferably in the range of about 1 to 2 N/mm 2 . In this connection, the peeling/shear fracture strength of concrete is about in the range of 3 to 5 N/mm 2 .
- the epoxy resin to be impregnated also serves as an adhesive.
- the bonding strength will become higher than the strength of the substrate to cause the aforementioned problems.
- the adhesive is preferably a one-component, non-solvent adhesive.
- This one-component, non-solvent adhesive may include an epoxy-urethane-based, non-solvent, moisture-setting type adhesive. This type of adhesive advantageously has no odor, no open time and long lifetime.
- the fixation of the reinforcing member to the structure member or the substrate can be performed without chamfering the structure member or the substrate and adjusting the unevenness of the surface of the structure member or the substrate.
- the fixation can be achieved without the large bonding strength as described above.
- the reinforcement effect can be maintained by the geometrical constraint.
- the adhesive 11 may be applied to the reinforcing member 5 at a working site of the bonding operation. Alternatively, the adhesive 11 may be applied to the reinforcing member 5 in advance, and stored until the bonding operation. In these reinforced structures, in an operation of detaching or peeling the adhesive, the substrate 3 or the reinforcing member is never damaged while leaving the adhesive layer thereon.
- the reinforcing member 5 When it is required to achieve the bonding constraint, as shown in FIG. 1, the reinforcing member 5 is installed in a range (reinforcing-member installation range 9) extending outward from a range (effective bonding constraint range 7) for reinforcing the structure member 1.
- the effective bonding constraint range 7 is selectively determined depending on a required performance or function of the structure member 1.
- the effective bonding constraint range 7 may be a portion of the surface of the structure member 1.
- the reinforcing member 5 is installed to form an envelope surface in the circumferential direction of the structure member 1 or to form a surface capable of being in contact with the portion of the surface of the structure member smoothly from the outside.
- the second mechanism or geometrical constraint is achieved, for example, by bonding both ends of a reinforcing member and installing the reinforcing member in such a manner that it encloses a given portion (periphery etc.) of a substrate 3, as shown in FIG. 3.
- the substrate 3 and the reinforcing member 5 is geometrically connected together, and constrained to one another.
- the length of the closed or looped reinforcing member is changed to generate a tensile force in the reinforcing member. If the reinforcing member is installed in conformity to the curvature or corner angle of the substrate, the tensile force will cause the frictional force or bearing force between the reinforcing member and the substrate so that the substrate and the reinforcing member exert a constraint force against deformation to one another.
- FIG. 4 is a perspective view showing a portion of a structure member 1 having the reinforcing member 5 installed thereon, wherein the reinforcing member 5 elastically constrains a substrate 3 having a gap 13.
- the gap is a crack or chap generated in the substrate 3.
- a gap width 15 (d) means the width of the gap 13.
- this peeled area is referred to as "free zone 19"
- the length of the free zone 19 associated with the region having a width 23 ( ⁇ w) of the reinforcing member 5 is referred to as "free length (a)”.
- the reinforcing member 5 and the structure member are constrained to one another.
- this constrained area is referred to as "constraint zone 21 ", and the length of the constraint zone 21 associated with the region having the width 23 ( ⁇ w) of the reinforcing member 5 is referred to as "constraint length (a)".
- a fixation length (s) is reduced from a constraint length (b) by a factor of a free length (a).
- an average value of shear stresses 18 acting between the surface of the substrate 3 and the non-peeled reinforcing member 5 is T f , and a tensile force, Young's modulus and thickness in the free zone 19 of the reinforcing member 5 being q, E f and t, respectively.
- the tensile force 17 and the resultant of the shear stresses 18 are balanced in the fixation zone, and thus the following relational expression is formulated.
- the reinforcing member is presupposed as an elastic body, and the elongation in the region of the fixation length is ignored because it is small as compared to the elongation in the free zone.
- ⁇ f max b t ⁇ f
- ⁇ f min 0.5 ⁇ f max
- ⁇ fmin is a stress at the time when the gap 13 is enlarged, and the gap width d reaches a value d max in the expression [3].
- the free length (a) is calculated as 1/2 of the constraint length (b). If the gap width d is increased at a value larger than d max , the expression [1] will be invalid in view of dynamical theories, the free length (a) will be sharply increased until a certain constraint such as geometrical constraint is given again.
- the change in the length (hereinafter referred to as "circumferential length") L of the envelope (the circumference of the envelope surface) can be presupposed as the change in the total value d of the gap width across the circumference.
- L 0 is the circumferential length before the generation of the gap.
- ⁇ f B 2 t ⁇ 3 , wherein B is the distance (sectional width) between the reinforcing members, and ⁇ 3 is a constraint pressure of the granular body.
- the value of the primary stress s 1 can be approximated as a value derived from dividing a compressive force by a pressure-receiving sectional-area.
- the value of the primary stress s 1 can be approximated as a value derived from dividing a compressive force by a pressure-receiving sectional-area.
- the relationship of the tensile force of the reinforcing member, the deformation causing a gap of the structure member and the fixation force is obtained from the expressions [3] to [7] and [9]. Further, since the deformation causing a gap would represent the level of the damage of the substrate, the relationship between the damage of the substrate and the tensile force (or strain) of the reinforcing member can also be obtained.
- the above model is unconfined by the type of the gap 13.
- the model is applicable to any gap 13 caused by any factor including a dynamical factor, such as bending or shear, and a material factor, such as temperature, dryness, expansion or deterioration.
- a dynamical factor such as bending or shear
- a material factor such as temperature, dryness, expansion or deterioration.
- shear shear chap, shear fracture surface, etc.
- the substrate 3 may be any construction material, such as reinforced concrete, steel framed reinforced concrete, steel frame, brick, block, gypsum or plaster board, precast concrete product, wood, rock, sand or resin.
- the substrate 3 may be an existing structural or non-structural martial or a newly installed material.
- the installation of the reinforcing member 5 may be a portion of the structure member as long as it is wider than an area (effective bonding constraint range 7) corresponding to the constraint zone 21 (constraint length (b)) for the crack or gap 13.
- an area of the effective bonding constraint range 7 in the reinforcing-material installation range 9 is an effective range.
- the reinforcement effect is superficially increased in proportion to the bonding strength.
- the bonding strength is set at a value close to the full strength of the substrate 3 or the reinforcing member 5, the substrate 3 or the reinforcing member 5 will be locally fractured before generation of a free length (a) to annul the reinforcement effect.
- the bonding strength is required to be set at a level causing no fracture in the substrate 3 and the reinforcing member 5 in the above process.
- the aforementioned model can be achieved if the reinforcing member 5 is not fractured by a stress concentration arising around a crack or gap or at a corner of the structure member 1 in connection with the generation and enlargement of the gap 1 in the structure member 1. Thus, it is also required to provide extensibility (large fracture strain) to the reinforcing member 5. While carbon fibers or aramid fibers have a large elastic coefficient and fracture strength, any material having a small fracture strain is not suitable as the reinforcing member in the first mode of embodiment and another after-mentioned mode of embodiment.
- the model can also be achieved if the reinforcing member brings out a sufficient performance even after the adhesive layer between the substrate and the reinforcing member is partly fractured.
- a continuous-fiber reinforcing member whose performance is defined under the condition of a structure in which a carbon or another fibers bound by resin are bonded on the surface of a substrate without float and wrinkle is not suitable as the reinforcing member in the first mode of embodiment and another after-mentioned mode of embodiment.
- the reinforcing member 5 is also required to have elasticity to bring out a control effect to the phenomenon that the gap 13 is opened and closed by a repeated alternate load.
- the quantification of the performance of a structure member 1 (structure-member performance model) will be described below.
- the dynamic performance and durability of the structure member can be quantified in consideration of the performance of a substrate and a desired reinforcement effect.
- the following description will be made in conjunction with one example in which a substrate 3 of the structure member 1 is a bar-shaped member made of reinforced concrete, and the substrate 3 is reinforced by the reinforcing member 5 and subjected to repeated shear.
- a shear load-deformation relationship has two extreme values, as described later in conjunction with FIGS. 5, 12, etc.
- FIG. 5 is a graph schematically showing the above relationship between load and deformation.
- the horizontal axis represents a deformation (deformation angle) in a structure member 1, and the horizontal axis represents a load acting on the structure member 1.
- the shape of the curve is described by ten parameters or Q max1 , ⁇ Q max , Q mid , Q min , Q max2 and R 1 to R 5 .
- Q max1 is an initial maximum vale of the load
- ⁇ Q max being the load in a limit state (design ultimate state etc.)
- Q min being a minimum value of the load
- Q mid being the load by which the bonding constraint is released and shifted to the geometrical constraint
- Q max2 being the load by which the reinforcing member 5 is fractured, or the deformation of the structure member 1 reaches at an extreme value and becomes unable to bear any load.
- R 1 to R 5 are the deformations corresponding to Q max1 , ⁇ Qmax, Q mid , Q min , Q max2 , respectively.
- the limiting point 27 (Q min , R 4 ) is a point where the structure member 1 is fractured by load, and starts exhibiting behaviors of a granular body.
- FIG. 6 is a graph showing the relationship between circumferential strain and deformation in the structure member.
- the horizontal axis represents a deformation (deformation angle) in the structure member 1
- the horizontal axis represents a circumferential strain in the structure member 1.
- the change in an apparent volume, or a volume associated with an envelope surface, of the structure member 1 is expressed by a circumferential strain (strain in the circumferential length of the section of the structure member 1 in a direction perpendicular to the axis thereof) and an axial strain (strain in the axis of the structure member 1).
- the circumferential strain ⁇ is changed as shown in the graph 29 in response to the change of the relationship between the load and the deformation in FIG. 5.
- the circumferential strain is gradually increased as the bonding is separated to increase a free zone 19.
- the circumferential strain is kept approximately constant by the geometrical constraint.
- the circumferential strain will be increased again because the structure member 1 behaves as a granular body.
- the axial strain is changed in the same manner as that of the circumferential strain.
- FIG. 7 shows the state when a region having the width 39 (H) of a structure member 31 reinforced by a reinforcing member 37 is divided into a first segmental member 33 a second segmental member 35 by a structural gap 41 (gap width 43 (d)), and the opposite ends of the divided structure member receive the action of a shear force 45 (Q).
- the reinforcing member 37 is installed to form an envelope surface in the circumferential direction of the structure member 31 or to form a surface capable of being in contact with the portion of the surface of the structure member smoothly from the outside.
- the shear force 45 is being transmitted between the first and second segmental members 33, 35 through the reinforcing member 37 in each section.
- FIG. 8 is a perspective view of the section (thickness 47 ( ⁇ H)) perpendicular to the axis of the structure member in FIG 7.
- Each of shear forces, reinforcing-member tensile stresses 51 ( ⁇ f ), and tensile forces 53 ( ⁇ cs ) of concrete and reinforcing bar acts on the structure member 31 (first and second segmental members 33, 35) and the reinforcing member 37.
- a first shear force to be transmitted from the upper surface of the first segmental member 33 to the lower surface of the second segmental member 35 through the reinforcing member 37 is defined as a transmission shear force 49 ( ⁇ Q f ).
- the difference between the shear forces in the upper and lower surfaces of the first segmental member 33 provides the transmission shear force 49 ( ⁇ Q f ). The same goes for the second segmental member 35.
- the thickness 47 ( ⁇ H) is infinitely small, and a body force and a moment with an arm having a length in the thickness direction are ignored. Further, given that there is no distributed load, and the reinforcing member 37 bears only the tensile stress 51 for the purpose of simplicity.
- FIG 43 is a chart showing properties (test specifications) of the tested columns, loading conditions, test results, and SRF reinforcement effects, on the nine cases under a constant axial force.
- FIG. 10 is a graph showing the relationship between horizontal load and deformation (restoring force characteristic) on the non-reinforced model column (Case 8).
- the horizontal axis represents a deformation ( ⁇ (mm)), and the vertical axis represents a horizontal load (Q (kN)).
- ⁇ mm
- Q max a maximum load was increased up to 237 kH
- Q max a maximum load was increased up to 237 kH (Q max ) in a cycle having a deformation angle of greater than 1.5%.
- FIG 11 a graph showing the relationship between horizontal load and deformation (restoring force characteristic) on the SRF-reinforced model column (Case 9).
- the horizontal axis represents a deformation ( ⁇ (mm)), and the vertical axis represents a horizontal load (Q (kN)).
- the model column was reinforced by bonding a reinforcing member formed of a polyester woven fabric having a thickness (t) of 4 mm, around the model column. The properties of the reinforcing member are shown in FIG 43.
- the bonding strength is about 1 MPa.
- the peak load is gradually reduced, and minimized (61: minimum point of the peak load) at a deformation angle of 64/400.
- the peak load is increased.
- FIG. 12 is a graph showing the relationship between the peak value of the horizontal load and the deformation in each of the loading cycles, on the nine cases under a constant axial force in FIG 43.
- the horizontal axis represents a deformation angle (R (%)), and the vertical axis represents a maximum horizontal load (peak load) in a positive direction in each of the loading cycles.
- Numerals in the figure indicate the case numbers illustrated in FIG. 43.
- Q mid /Q max and Q min /Q max were calculated based on the above maximum point, minimum point and gradient-change point. The result is shown in FIG 62.
- Q mid /Q max becomes approximately equal to a theoretical value of 0.5 according to the expression [4].
- Q min is reduced from Q mid only by about 10% thereof. This result supports the validity of the aforementioned quantification of the effect of the reinforcing member.
- FIG. 13 is a graph showing the relation between structure-member circumferential-length elongation strain and deformation.
- the horizontal axis represents a deformation angle (R (%)), and the vertical axis of a structure-member circumferential-length elongation strain ( ⁇ (%)).
- R (%) a deformation angle
- ⁇ (%) the vertical axis of a structure-member circumferential-length elongation strain
- the design calculation can be performed according to the aforementioned quantification models of the reinforcement effect and the performance of a structure member having a reinforcing member installed thereon.
- FIG. 62 shows the calculated K (reinforcement efficiency).
- a design strength ⁇ fd of the reinforcing member was calculated back according to a method defined in the design/installation manual for continuous-fiber reinforcement of Architectural Institute of Japan.
- FIG 43 shows the ratio (reinforcement efficiency: ⁇ fd / ⁇ fmax ) of the design strength ⁇ fd to a fracture strength ⁇ fmax of a SRF reinforcing member.
- a shear strength S after reinforcement was calculated by determining a shear margin from a roughness coefficient. The calculation was also performed on the assumption that a yield deformation angle was 1/250 in all of the cases.
- a reinforcing-member strain ( ⁇ f ) was calculated from an actually measured shear load (Q) (see the expression [11]), and then a constraint rate (a/L 0 ) was calculated from the calculated reinforcing-member strain ( ⁇ f ) and an actually measured circumferential strain ( ⁇ ) (see the expression [6]).
- This constraint rate (a/L 0 ) is shown in FIG 62.
- the constraint rate (a/L 0 ) is the ratio of a free length (a) to a circumferential length (L 0 ).
- the tested reinforced column receives a shear force from one direction.
- the constraint rate (a/L 0 ) is theoretically 0.5.
- the tested reinforced column has a constraint rate (a/L 0 ) ⁇ 0.5 in Cases 3 and 5, and a constraint rate (a/L 0 ) > 0.5 in Cases 9 and 13.
- a bonding constraint in Cases 3 and 5 having a deformation angle R 2 of 1 to 2% is still effective, a bonding constraint in Cases 9 and 13 having a deformation angle R 2 of 4 to 6% is released and completely shifted to a geometrical constraint.
- FIGS. 39 and 40 are design flowcharts for a reinforcement amount in a process of reinforcing a structure member through a method of the present invention. With reference to the flowcharts in FIGS. 39 and 40, a method of determining reinforcement parameters will be described below.
- limit conditions of the weight, shape, function and others of a structural body are first determined (Step 301). Concurrently, the amplitude, cycle or period, duration and energy of a sudden external force likely to act on the structural body are determined (Step 302). Among the sudden external force likely to act on the structural body, a burden share to be bome by a substrate of the structural body, such as reinforcing bar and concrete, is also determined (Step 303).
- the parameters of the structure member are determined in consideration of the data determined in Steps 301 to 303 (Step 304).
- the parameters of the structure member may be determined using conventional structural design/calculation methods or any other suitable reinforcement manuals.
- Step 305 a burden share to be bome by a method of the present invention is determined.
- this step is intended to determine the type, property, and magnitude (amplitude, period, duration, and energy) of the sudden external force to be bome by the method, structure or material of the present invention.
- These data may be obtained by subtracting the energy of a sudden external force bearable with other factors than the reinforcement according to the method of the present invention (the burden share of the substrate etc. determined in Step 303) from the total energy of the sudden external force likely to act on the structural body in the durable term thereof, which has been determined in Step 301.
- the reinforcement of the present invention is used in a structural design for a new construction, the materials and/or parameters of a structure member can be determined in an economically advantageous manner by a factor of the reinforcement of the present invention.
- the data in Step 305 are determined from the data determined in Steps 302 and 303.
- such data may be obtained by subtracting a sudden external force bearable with other factors than the reinforcement according to the method of the present invention from the total energy of the sudden external force likely to act on the structural body in the durable term thereof, as with the process (a).
- Step 306 the amplitude and energy of a sectional force to act on the structure member are calculated (Step 306). Specifically, based of the type, property and magnitude of the sudden external force determined in Step 302, the amplitude and magnitude of a sectional force (shear force, axial force, bending moment, etc.) to act on a structure member including a reinforced structure member and other structure members, and a deformation (shear strain, axial strain, bending strain, etc.) of the structure member. Concurrently, the displacement amplitude and vibrational energy of the entire structure body to be induced by the sudden external force are calculated (Step 307).
- the data in Step 306 or 307 may be rigorously calculated by performing a structural analysis calculation, such as a finite element method or frame analysis method taking account of a restoring force characteristic of a reinforced structure member and other structure members as shown in FIG 51.
- a structural analysis calculation such as a finite element method or frame analysis method taking account of a restoring force characteristic of a reinforced structure member and other structure members as shown in FIG 51.
- the data in Step 306 or 307 may be calculated by simplifying a structural system and setting assumptions such as energy formulas, as in practical structural designs. Except that an associated deformation range is wider than that in a conventional calculation, the calculations in Steps 306 or 307 can be performed in the same manner as that in a structural design for a structure member having a known restoring force characteristic.
- Step 308 the relationship of a reinforcement amount, a restoring force characteristic and an axial strain of the reinforced structure member is determined (Step 308).
- the data in Step 308 are determined by the calculations in Steps 306 and 307.
- Step 308 it is generally required to perform a feedback from 310 to Steps 306 and 307 through Steps 308, as indicated by the dashed lines of FIG 59.
- Step 309 limit conditions of the function, usability, recoverability and others of the structural body after the action of the sudden external force such as a seismic force are determined (Step 309), and the determined limit conditions are compared with the displacement amplitude and vibration energy of the structural body calculated in Step 307 to determine reinforcement parameters (Step 310).
- the reinforcement parameters are determined by comparing the deformation of the structural body calculated in Steps 306 to 308 with an allowable deformation amount to be derived from the conditions determined in Step 309 or the use conditions of the structural body after the action of the sudden external force such as a seismic force.
- Step 310 is performed in consideration of the limit conditions of the weight, shape, function and others of the structural body which have been determined in Step 301.
- Step 309 If the conditions in Step 309 are determined based on the policy of simply preventing collapse against a large earthquake, the allowable deformation can be set at a large value. If a large deformation involves the risk of disaster such as derailment even immediately after occurrence of a large earthquake, as in an elevated railroad for the bullet train, the reinforcement amount will be determined in consideration of such a factor.
- the reinforcing member can be designed by the following process.
- the reinforcement design has to be performed using a sufficient safety factor for a fracture strain because there is a possibility of causing a strain several times larger than the reinforcing-member strain ⁇ f in the expression [11].
- a shear force transmitted by a substrate a shear force transmitted by concrete. reinforcing bar or the like, etc.
- the subtraction of this shear force may be set at 0 (zero) on the safe side.
- a load-withstanding capacity of the structure member after the structure member goes beyond the above design ultimate state can also be calculated using the expressions [8] and [9].
- the performance of the structure member and the reinforcement amount are experimentally checked as needed as in a conventional design for reinforced concrete members.
- a structure member can be produced using a substrate consisting of a material, such as brick or block, which has been considered as a non-structural material,
- the material of the reinforcing member is selected such that the Young's modulus of the reinforcing member is less than that of the substrate, as described above.
- the Young's modulus of the reinforcing member is excessive low, the thickness of the reinforcing member required for obtaining a desired reinforcement effect will be increased as shown in the expressions [3] and [11].
- the material of the reinforcing member is selected from one having a Young's modulus preferably in the range of about 1/2 to 1/20, more preferably about 1/5 to 1/10, of that of the substrate.
- the bonding constraint mechanism becomes effective for a larger gap and can suppress the deformation (circumferential strain) of the substrate at a smaller value as the reinforcing member has a larger Young's modulus in the design ultimate state.
- This deformation (circumferential strain) of the substrate is quantified by the expressions [3] and [11].
- FIG 9 is a graph showing a stress-strain relationship of the reinforcing member.
- the horizontal axis represents a strain ( ⁇ ) of the reinforcing member, and the vertical axis represents a stress ( ⁇ f ) of the reinforcing member.
- the reinforcing member is required to have extensibility (large fracture strain).
- the design for the reinforcing member and others is preferably performed in consideration of the curve of the stress-strain relationship as shown in FIG. 9.
- the ratio 59 ( ⁇ fu / ⁇ fu ) of a stress ⁇ fu of the reinforcing member to ⁇ fu of the reinforcing member in a design ultimate state 57 of a structure member is defined as a Young's modulus E f of the reinforcing member in the design ultimate state, and the design of the reinforcing member and others is performed using the Young's modulus E f , and a fracture strain ⁇ max and fracture stress (strength) ⁇ max of the reinforcing member
- the reinforcing member is selected to satisfy a desired performance of the reinforced structural with reference to the expressions [1] to [9].
- a polyester woven fabric or the like When a polyester woven fabric or the like is used as the reinforcing member, it may be heated to provide a tensile force thereto, and then cooled while maintaining the tensile force or subjected to a treatment for impregnating the reinforcing member with resin (resin impregnation treatment), to provide E f larger than ⁇ fu / ⁇ fu .
- the reinforcing member subjected to the above treatment can have a higher reinforcement efficient (reinforcement effect per unit thickness) than that of the reinforcing member without the treatment, to achieve a reduced material cost.
- FIG 14 is a perspective view of a walled column with the reinforcing member installed thereon.
- the walled column comprises a column 71 and a wall 73.
- the reinforcing member 75 is installed in such a manner it is wound around the column 71 and bonded on a reinforcing-member installation range 79.
- the reinforcing-member installation range 79 has a larger area than that of an effective bonding constraint range 77.
- the effective bonding constraint range 77 corresponds to a given constraint length (b).
- the wall 73 is formed with no through-hole for installing the reinforcing member 75.
- a safety factor is 2
- a design constraint length (b d ) is about 40 cm.
- FIG 15 is a sectional view of the walled column 69 in FIG 14.
- the design constraint length (b d ) corresponds to the effective bonding constraint range 77 in FIGS. 14 and 15.
- a restoring force characteristic in the state after the shear force goes beyond the design ultimate state to cause fracture of the walled column 69 and thereby the bonding restraint is completely released and shifted to the geometrical restraint can be calculated according to the expressions [8] an [9].
- the limit ((Q max2 , R 5 ): FIG. 5) of the validity of the geometrical restraint is determined by smaller one of the strength of the reinforcing member and the strength of the substrate at the joint portion. At any rate, the geometrical restraint can be maintained up until the limit (Q max2 , R 5 ) without forming a hole or the like in the walled column 69 and penetrating the reinforcing member therethrough.
- FIG 16 is a sectional view of the walled column 69 in FIG 14. While the reinforcing member 75 installed around the column 71 is opened at the joint plane between the column 71 and the wall 73, a portion of the column 71 in this open zone 183 is constrained by the wall 73 having the reinforcing member 75 installed thereon. Thus, the entire circumferential of the column 71 is constrained by the reinforcing member 75 and the wall 73 having the reinforcing member 75 installed thereon. In this case, the geometrical constraint is achieved in an effective geometrical constraint range 81.
- a given reinforcement effect can be obtained by installing the reinforcing member on only one of the surfaces of a structure member such as wall.
- a earthquake-resisting wall may be formed by placing a pair of boards, such as precast concrete boards, in parallel with one another between two existing columns to form a wall, pouring concrete or filling sands or the like into the space between the boards, and installing the reinforcing member around the wall and/or the columns.
- the reinforcing member having a given rigidity and extensibility is installed a portion of the surface of a structure member to be reinforced, to reinforce the structure member.
- the reinforcement can be applied to a structure member having any shape such as a convexo-concave or irregular shape.
- the reinforcing member can be installed without forming any hole or the like in a structure member subject to reinforcement. Therefore, a reinforced structure excellent in toughness and load-withstanding capacity can be constructed quickly and readily at a low cost.
- the reinforcement effect of the reinforcing member and the performance of the reinforced structure with the reinforcing member can be quantified and/or evaluated according to the aforementioned reinforcement effect model and structure-member performance model.
- the reinforcing member can be adequately selected and designed depending on a structure member subject to reinforcement.
- the reinforcing member and the adhesive according to the first mode of embodiment can be effectively selected depending the material, category and type (existing or new construction, etc.) of a structure member.
- the labor load and cost for constructing the reinforced structure having a desired performance and preparing/installing the reinforcing member having a desired reinforcing effect or quake-resistance effect can be constructed can be reduced while shortening a construction period.
- a strip-shaped polyester belt 199 as shown in FIG 21 may be used as a substitute for the reinforcing member 75.
- the material of the polyester belt 199 may be polyester-based fibers for use in bell rope or the like. While a reinforcing sheet such as a construction sheet has a strength in the range of 500 to 1000 kgf/3 cm width, the polyester belt 199 has a strength of about 15000 kgf/5 cm width.
- FIG 17 is a perspective view of an H-shaped structure member 143 after reinforcement. As shown in FIG 17, the H-shaped structure member 143 is reinforced using a reinforcing member 145 and a granular filler material 147.
- the sheet-shaped reinforcing member 145 is shaped into a cylindrical shape and disposed around the H-shaped structure member 143 to form a space therebetween.
- the granular filler material 147 is filled in the space between the H-shaped structure member 143 and the reinforcing member 145.
- a fiber or rubber-based sheet material may be used for the reinforcing member 145.
- the filler material 147 may be a natural granular material, such as sands, or an artificial granular material, such as resin.
- the glandular filler material 147 transmits a stress to the reinforcing member 145 while being deformed in connection with energy loss.
- the conventional reinforcing techniques such as continuous fibers or steel-plate wrapping
- the bonding or fixation may be performed in a temporary level allowing the shape of the filler material to be held under ordinary loading or in earth tremor.
- This type of reinforced structure may be used to reinforce a structure member having a complicated sectional shape, as well as the H-shaped structure member 143.
- the granular filler material 147 transmits the apparent volume expansion to the reinforcing member to provide enhanced reinforcement effect.
- the granular filler material may be formed of an inorganic noncombustible material having high heat capacity to have an additional effect of protecting the H-shaped structure member 143 from heat.
- FIG 18 is a perspective view of a hollow structure member 149 after reinforcement. As shown in FIG. 18, the hollow structure member 149 is reinforced using a reinforcing member 145 and a granular filler material 147.
- the sheet-shaped reinforcing member 145 is installed on and around the outer surface of the cylindrical hollow structure member 148.
- the inside of the hollow structure member 149 is filled with the granular filler material 145.
- a fiber or rubber-based sheet material may be used for the reinforcing member 145.
- the filler material 147 may be a natural granular material, such as sands, or an artificial granular material, such as resin.
- the granular filling material 147 is installed to fill the space of the hollow structure member 149.
- the glandular filler material 147 transmits a stress to the reinforcing member 145 while being deformed in connection with energy loss.
- the granular filler material 147 is installed inside the structure member to provide enhanced reinforcement effect.
- the filler material acts to transmit to the reinforcing member 145 an apparent volume expansion cased when the hollow structure member 149 is fractured in connection with energy loss.
- the hollow structure member in the above example has a circular sectional shape, the present invention is not limited to such a shape.
- FIG. 19 is a partial sectional view of a reinforced member 181.
- the member 181 is reinforced by use of a protective reinforcement 183, a reinforcement 185, a reinforcement 187, and a protective reinforcement 189.
- the protective reinforcement 183, the reinforcement 185, the reinforcement 187, and the protective reinforcement 189 are sequentially, from inside to outside, disposed on the member 181.
- the protective reinforcement 183 is disposed in order to protect the reinforcements 185 and 187 and the protective reinforcement 189 from the action of the member 181.
- the protective reinforcement 183 is made of a material, such as a resin, which has a function to prevent separation of alkali from the member 181.
- the protective reinforcement 189 is disposed in order to prevent a deterioration in the function of the protective reinforcement 183 and the reinforcements 185 and 187 which would otherwise result from the action of substances in the external environment.
- the protective reinforcement 189 is made of epoxy, urethane, or a like resin to thereby prevent a deterioration of the reinforcements disposed inside the same.
- a fireproof belt can also be used as the protective reinforcement 189.
- the reinforcement 185 and the reinforcement 187 differ in a reinforcement effect on the member 181.
- the reinforcement 187 is made of polyester fiber or the like, and the reinforcement 185 is made of a resin or fiber impregnated with resin.
- the reinforcement 187 exhibits a reinforcement effect at up to a large strain (up to about 15%) of the member 181, whereas the reinforcement 185 exhibits a reinforcement effect at a low strain (not greater than 1 %) of the member 181.
- the reinforcement When the member 181 is to be reinforced merely by use of a polyester fiber reinforcement, the reinforcement must assume a large thickness in order to exhibit a reinforcement effect at the stage of a small strain of the member 181, since the reinforcement is smaller in Young's modulus than the member 181.
- the polyester fiber reinforcement thinner than that used solely for reinforcing the member 181 can exhibit a reinforcement effect even at a small strain (not greater than 1%) of the member 181.
- the reinforcement 185 can exhibit a reinforcement effect at small strain.
- the protective reinforcement 183 assumes, as needed, a function for transmitting a shear force induced between the surface of the member 181 and the reinforcement 185.
- a resin primer is used as the protective reinforcement 183.
- the reinforcement 185 and the reinforcement 187 may differ in a mechanism for yielding a reinforcement effect so as to exhibit a reinforcement effect under different load conditions and over the range of deformation. For example, there are combined a method in which part of a shear force imposed on the member 181 is directly borne by a reinforcement, and a method in which the expansion of an apparent volume of the member 181 is restrained.
- Material and configuration of the reinforcement 187 can be such that a reinforcement effect is yielded through restraint of the expansion of an apparent volume.
- the reinforcement 185 is made of an iron plate, carbon fiber, aramid fiber or the like. Through direct transmission of a shear force between the member 181 and the reinforcement 185, the shear force is shared between the member 181 and the reinforcement 185, whereby the member 181 is reinforced.
- a polyester sheet or belt or the like whose rigidity is enhanced through impregnation with resin or through application of adhesive to the entire surface thereof can be used as the reinforcement 185. This yields a merit in that the reinforcement 185 and the reinforcement 187 can be continuously laid.
- FIG. 20 is a graph showing the relationship between load and deformation with respect to the member 181 which is reinforced by means of a multilayer configuration as shown in FIG. 19.
- the vertical axis represents load
- the horizontal axis represents deformation.
- the load represents section forces of the member 181, such as axial force, bending moment, shear force, etc.
- the deformation represents deformations corresponding to the section forces; specifically, axial contraction, flexural modulus, shearing strain, etc.
- a curve 193 which represents the case of reinforcement by means of multilayer configuration indicates that the member 181 has load bearing capacity over a wider range of deformation as compared to the case of no reinforcement employed as represented by a curve 191.
- FIG. 20 shows an ordinary example in which the effective deformation range of the reinforcement 185 does not overlap with that of the reinforcement 187; i.e., a slight reduction in load bearing capacity occurs between an effective range195 of the reinforcement 185 and an effective range 197 of the reinforcement 187.
- the reduction of load bearing capacity can be avoided by overlapping the effective deformation ranges of the reinforcements 185 and 187.
- the member 181 is not limited to a concrete member or the like but may be the filler 147 shown in FIGS. 17 and 18. In this case, through employment of the filler 147 that yields an effect equivalent to that yielded by the protective reinforcement 183, the protective reinforcement 183 may be omitted.
- a beltlike reinforcement of high strength and rigidity such as the polyester belt 199
- the polyester belt 199 can be woven into texture that exhibits greater Young's modulus per unit width as compared with a polyester sheet
- the polyester belt 199 can be used as the reinforcement 185, which exhibits a reinforcement effect at the stage of small strain.
- strain is 2% under a load of 2500 kgf.
- a column 205 shown in FIGS. 22 to 25 corresponds to the member 181 of FIG 19.
- a reinforcement method by use of the polyester belt 199 as shown in FIGS. 22 to 25 will be described in the subsequent section of an eighth embodiment.
- FIG 21 is a plan view of the polyester belt 199
- FIGS. 22 and 23 are perspective views showing examples of the column 205 reinforced by use of a beltlike reinforcement 201
- FIG 24 is an elevation of the column 205 shown in FIG 23.
- a plurality of beltlike reinforcements 201 are disposed at predetermined intervals on the column 205 in such a manner as to be wound about the column 205. End portions of each of the beltlike reinforcements 201, which are wound about the column 205, can be connected together by means of bonding and/or a clasp, which are mechanical joints. Use of mechanical joints can implement reinforcement in a short period of time and is thus suited for urgent reinforcement to be performed immediately after an earthquake disaster.
- Beltlike reinforcements 203 bonded axially to the column 205 can be expected to yield the effect of controlling a crack(s) extending along a direction intersecting the same.
- the beltlike reinforcement 201 is compactly wound about the column 205 shown in FIGS. 23 and 24. While tension is imposed on the beltlike reinforcement 201 in the direction of arrow C, the beltlike reinforcement 201 is wound onto the column 205 in the direction of arrow D, thereby enhancing a reinforcement effect.
- the beltlike reinforcement 201 is bonded directly to the column 205. Comer portions of the column 205 are not particularly required to be chamfered or to undergo like processing in order to avoid breaking textile at the comer portions. However, a beltlike reinforcement (not shown) bonded to a comer portion of a member in parallel with the edge of the comer portion can be expected to yield the effect of easing stress concentration of an edge portion on a reinforcement.
- the beltlike reinforcement 201 is wound onto an upper end portion 207 and lower end portion 211 of the column 205 in parallel with the circumferential direction of the column 205 and is spirally wound onto a general portion 209 such that, as the beltlike reinforcement 201 is wound one turn, it axially advances by the width thereof, whereby the beltlike reinforcement 201 can be wound about the column 205 compactly and evenly.
- the winding direction (clockwise or counterclockwise) can be altered so as to wind the beltlike reinforcement 201 onto the column 205 in two layers, three layers, etc., thereby enhancing a reinforcement effect.
- the reinforcing member In order to allow the reinforcing member to be in close contact with the substrate in the above winging manner, it is required that the reinforcing member can be bent at an angle equal to or greater than the comer angle of the column, and sheared at an angle equal to or greater than the displacement angle between the parallel winding and the spiral winding. In a typical column, the bending angle and the displacement angle are 90-degree or less and 2-degree or less, respectively. When a reinforcing member is installed in a crossed manner as described later in connection with FIG. 56, it is preferable that the reinforcing member can be sheared at a large angle.
- FIG. 25 is a sectional view of a surface portion of the column 205 shown in FIGS. 22 to 24. As shown in FIG. 25, the beltlike reinforcement 201 is bonded directly to the column 205 by use of an adhesive 213.
- the beltlike reinforcement 201 shown in FIGS. 22 to 25 is, for example, the polyester belt 199 shown in FIG. 21.
- the polyester belt 199 is made of polyester fiber, which is a material for a strap or the like.
- the polyester belt 199 is used particularly in view of the following: being higher in rigidity and strength than a civil engineering sheet, the polyester belt 199 restrains an increase in the width of crack in the column 205 and controls the deformation of an apparent volume for the range of small strain.
- FIG. 26 is a view showing an effective bond length between the beltlike reinforcement 201 and a crack 215.
- the crack 215 appears on the surface of the member.
- the crack 215 is made on the surface of the column 205, to which the beltlike reinforcement 201 is bonded directly.
- the belt width 219 of the beltlike reinforcement 201 is w.
- a force which attempts to expand the crack 215; i.e., tension 221, is imposed on the beltlike reinforcement 201 in the amount of q per belt.
- the beltlike reinforcement 201 restrains crack width 217 to d or less.
- Restraint length 225 is the length of a single side in the case a rectangular cross section, as in the column 205, and is the length of an arc corresponding to a central angle of about 90 degrees in the case of a circular cross section. When these lengths are significantly large as compared with belt width 219 (w) of the beltlike reinforcement 201, restraint length 225 is a length along which an effective bonding force is not zero.
- restraint length 225 extends to another surface of the member.
- the beltlike reinforcement 201 When a material which is inexpensive and has excellent stretchability, such as the polyester belt 199, is used as the beltlike reinforcement 201, since the Young's modulus of the material is about one-tenth that of concrete or one-hundredth that of iron, the following problem is involved. Even when the adhesive 213 having large average shear force ⁇ is used for bonding, the material encounters difficulty in sharing with a member a force which is elastically imposed on the member, without formation of the crack 215. However, when a reinforcement effect is particularly needed at the stage of small deformation, a polyester belt or the like is impregnated with resin to thereby enhance the rigidity of the reinforcement. The thus-prepared reinforcement is used together with an epoxy resin adhesive.
- the polyester belt 199 has a woven body of a weft double weave using a polyester-fiber yam with 1700 dtex (dcitex).
- the column 205 is made of reinforced concrete. Concrete has a compression fracture strength of 13.8 MPa (135 kgf/cm 2 ), a Young's modus of 19500 MPa, and a direct shear strength of about 2.6 MPa. The reinforcing member was installed without performing any chamfering and any adjustment of surface unevenness.
- Rubiron 101 (one-component: available from Toyo Polymer Co.) was used as an adhesive.
- the layer of the adhesive is 1 mm.
- the adhesive has a bonding strength of about 1 MPa (10 kgf/cm 2 ), and a specific gravity of 1.4.
- a part of the adhesive is infiltrated into the texture of the polyester belt 199, and cured.
- the entire adhesive of 1 mm thickness enters into the void of the polyester belt 199, it will occupy only about 70% of the void of the polyester belt 199, and the breathability or air-permeability of the reinforcing member can be maintained.
- Rubiron 101 is not a non-solvent adhesive, it has been experimentally verified that the same reinforcement effect can be obtained even using a non-solvent adhesive having a bonding strength equivalent to that of Rubiron 101.
- the beltlike reinforcement 201 is the polyester belt 199 having a width of 64 mm and a thickness of 4 mm;
- the adhesive 213 is LUBIRON, which is the trade name of an epoxy urethane adhesive produced by Toyo Polymer Corp.
- FIG. 27 is a schematic view of the column 205 subjected to an axial force, bending, and a shear force.
- FIG. 28 is a view showing a force which attempts to expand the crack 215 formed in the column 205. Described below is a reinforcement effect to be yielded in the case where the column 205 is reinforced by use of the polyester belt 199, which serves as the beltlike reinforcement 201, according to the method of FIG. 24; and the thus-reinforced column 205 is loaded in the following manner: while axial force 229 (P) is applied to the column 205, a horizontal force is applied to the column 205 so as to repeatedly generate bending moment 231 (M) and shear force Q.
- P axial force 229
- M bending moment 231
- the column 205 is assumed to be an ordinary structural column. Conditions of study are as follows: shear force 227 (Q) is horizontally imposed on the column 205 at the middle of height h; i.e., at height (h/2); and the upper and lower ends of the column 205 slide horizontally without involvement of rotation. As a result, a horizontally even shear force (resultant force Q) and an axial force (resultant force P) are generated in the column 205.
- FIG. 29 is a schematic view showing the deformation of the column 205.
- FIGS. 30 to 35 show experiment results, in which horizontal displacement ⁇ h 239 represents the horizontal displacement of the column 205; and vertical displacement ⁇ v 241 represents the vertical displacement of the column 205.
- FIG. 30 is a graph showing the relationship between horizontal force Q of the column 205 and an envelope indicative of displacement hysteresis of the column 205.
- FIG. 31 is a graph showing the relationship among the horizontal displacement of the column 205, the vertical displacement of the column 205, and a horizontal force.
- FIG. 32 is a graph showing restoring-force characteristics of the column 205.
- the horizontal axis represents horizontal displacement ⁇ h (239) of the column 205
- the vertical axis represents horizontal force Q (shear force 227)
- the horizontal axes represent horizontal displacement ⁇ h (239) of the column 205 and the angle of deformation
- the vertical axis represents horizontal force Q (shear force 227).
- a reinforcement-absent curve 243a is an envelope as observed when the column 205 is not reinforced with the beltlike reinforcement 201
- a reinforcement-present curve 243b is an envelope as observed when the column 205 is reinforced.
- the reinforcement-present curve 243b is an envelope along the following points on a hysteretic loop 253 shown in FIG 32: a point corresponding to a level 255a equivalent to the level of the Great Hanshin Earthquake Disaster, a point corresponding to a level 255b equivalent to two times the level of the Great Hanshin Earthquake Disaster, a point corresponding to a level 255c equivalent to three times the level of the Great Hanshin Earthquake Disaster, a point corresponding to a level 255d equivalent to five times the level of the Great Hanshin Earthquake Disaster, etc.
- the horizontal axis represents horizontal displacement ⁇ h (239); the upward vertical axis represents horizontal force Q (shear force 227); and the downward vertical axis represents vertical displacement ⁇ v (241).
- a reinforcement-absent curve 243a and a reinforcement-present curve 243b are envelopes similar to those shown in FIG. 30.
- the reinforcement-absent curve 245a shows vertical displacement ⁇ v of the column 205 which is not reinforced with a beltlike reinforcement.
- the reinforcement-present curve 245b shows vertical displacement ⁇ v of the column 205 which is reinforced with the beltlike reinforcement 201 (polyester belt 199).
- the reinforcement-absent curve 243a which shows horizontal force Q of the unreinforced column 205
- the reinforcement-absent curve 245a which shows vertical displacement ⁇ v
- the beltlike reinforcement 201 exhibits a reinforcement effect; i.e., the beltlike reinforcement 201 bears substantially the entire shear force in a horizontal-displacement region ranging from a horizontal displacement corresponding to Q max2 to a horizontal displacement corresponding to Q min .
- the experimentally obtained value of minimum horizontal force Q min appearing on the reinforcement-present curve 243b is lower than a calculated value of 9 tf, which is obtained through calculation using the models of FIGS. 27 and 28. This can be said to be an experimental error and implies the occurrence of a drop in strength at the bond area between the concrete surface of the column 205 and the beltlike reinforcement 201 (polyester belt 199).
- the value of maximum shear force Q max2 is substantially equal to a calculated value of 18 tf.
- Displacement amplitude ⁇ hc 247 is horizontal displacement ⁇ h at around a point corresponding to the level 255c equivalent to three times the level of the Hyogo-Ken Nanbu Earthquake on the hysteretic loop 253 shown in FIG. 32; i.e., about 140 mm (angle of deformation 0.15 rad).
- FIG. 33 is a graph showing the relationship between cumulative horizontal displacement ⁇ h and hysteretic absorbed energy W in the column 205.
- FIG 34 is a detailed view of FIG 33.
- the horizontal axis represents cumulative horizontal displacement ⁇ h
- the vertical axis represents hysteretic absorbed energy W.
- Cumulative horizontal displacement ⁇ h which is represented by the horizontal axis in FIGS. 33 and 34, was calculated by the equation shown below.
- i is the number of steps in data recording
- n is the current number of steps.
- Cumulative horizontal displacement ⁇ h is calculated as an indicator of a position on the hysteretic loop 253 shown in FIG 51.
- the curve of hysteretic absorbed energy 257 shown in FIG. 33 shows hysteretic absorbed energy which is calculated from the experimentally obtained hysteretic loop 253 shown in FIG. 51, by use of Eq. 28).
- the straight lines indicative of a level 259a equivalent to the level of the Great Hanshin Earthquake Disaster and a level 259b equivalent to five times the level of the Great Hanshin Earthquake Disaster represent values which are calculated by Eq. 29) for comparison with the curve of hysteretic absorbed energy 257.
- FIG 53 additionally show values which are calculated by Eq.
- FIG. 35 is a graph showing the relationship between calculated cumulative horizontal displacement ⁇ h and vertical displacement ⁇ v by use of Eq. 27).
- the horizontal axis represents cumulative horizontal displacement ⁇ h
- the vertical axis represents vertical displacement ⁇ v (241 ).
- cumulative horizontal displacement ⁇ h is about 1500 mm.
- vertical displacement ⁇ v is not greater than 5 mm (strain 0.5%) until cumulative displacement reaches about 1500 mm at the vertical-displacement inflection point 251.
- a conventional reinforcement method in which a member is wrapped with reinforcement is characterized in that, in order to prevent formation of cracks, a reinforcement material, such as carbon fiber or wrapping iron plate, having rigidity equivalent to or greater than that of a major dynamic component of the member is bonded directly to the surface of the member by use of resin or the like.
- the beltlike reinforcement 201 such as the polyester belt 199, is bonded directly to a member, such as the column 205 is not adapted to suppress formation of the crack 215 on the member surface but is adapted to restrain crack width 217 to an effective value; for example, to about 2 mm, whereby the functional impairment of a member is controlled to thereby maintain usability and safety of a structure.
- a method in which a high-rigidity material, such as the polyester belt 199, is bonded directly to the surface of a member is intended to enhance the effect of maintaining the shape of the member with respect to deformation accompanied by finite crack 215.
- this effect is enhanced in proportion to the circumferential rigidity of a reinforcement, and the enhancement of the effect is limited by the magnitude of a shear force to be transmitted between the surface of the member and the reinforcement. Accordingly, through a high-rigidity reinforcement being bonded directly to a member, a reinforcement effect can be enhanced.
- the beltlike reinforcement 201 used in the ninth embodiment is not limited to the polyester belt 199. Any material having strength and rigidity equivalent to those of the polyester belt 199 can be used.
- the reinforcement method is such that, through control of an increase in crack width 217, the expansion of an apparent volume of a member is restrained.
- the method is identical to that of the previous application.
- the method employs the mechanism of restraining variation in shape and axial strain and is verified theoretically and experimentally, thereby indicating high practical viability thereof.
- FIG. 36 is a perspective view showing a state in which connecting reinforcements 269a and 269b are disposed on the joint between a column 261 and a beam 263.
- the beam 263 is joined to the column 261 at right-hand and left-hand side surfaces 265b.
- the joint between the column 261 and the beam 263 is reinforced by use of two sheetlike connecting reinforcements 269a and four connecting reinforcements 269b.
- the connecting reinforcement 269a assumes the form of a sheet and is bonded to the column 261 and the beam 263 in such a manner as to cover the joints between the side surfaces 265b of the column 261 and the side surface 267a of the beam 263.
- a central portion of the connecting reinforcement 269a is bonded to a side surface 265a of the column 261 and the right-hand and left-hand side surfaces 265b adjacent to the side surface 265a.
- Opposite end portions of the connecting reinforcement 269a are bonded to the side surface 267a of the beam 263.
- the connecting reinforcement 269a assumes the form of a sheet and is bonded to the column 261 and the beam 263 in such a manner as to cover the joint between the side surface 265b of the column 261 and the side surface 267b of the beam 263.
- the connecting reinforcements 269a and 269b are, for example, stretchable, fibrous or rubber sheet materials.
- the connecting reinforcements 269a and 269b are not necessarily sheetlike reinforcements but may assume the form of a beltlike reinforcement, such as the polyester belt 199.
- the thickness, width, length, etc. of the connecting reinforcements 269a and 269b, either sheetlike or beltlike, are determined to provide a required amount of reinforcement.
- the connecting reinforcements 269a and 269b may be bonded to the column 261 and the beam 263 in a tentative condition but may be bonded in such a manner as to yield strength.
- the displacement amplitude of a structure depends greatly on the deformation of a member-to-member joint.
- use of the latter bonding is practical.
- FIG. 37 is a perspective view showing a state in which a beltlike reinforcements 271a and 271b are disposed on the joint between the column 261 and the beam 263.
- a single beltlike reinforcement 271a and two beltlike reinforcements 271b are disposed in such a manner as to cover the connecting reinforcements 269a and 269b which are disposed as shown in FIG. 36.
- the beltlike reinforcement 271a is disposed on the exterior of a bigger member; i.e., on the exterior of the column 261.
- the beltlike reinforcement 271a is wound onto the column 261 in such a manner as to be continuously wound between a portion of the column 261 located above the joint between the column 261 and the beam 263 and a portion of the column 261 located below the joint while obliquely crossing the joint.
- the beltlike reinforcement 271b is disposed on the exterior of a thinner member; i.e., on the exterior of the beam 263.
- the beltlike reinforcement 271b is independently wound about the right-hand and left-hand beams 263 joined to the column 261.
- the beltlike reinforcements 271a and 271b are disposed in two layers and cross-wound onto the joint between the column 261 and the beam 263.
- FIG. 38 is a sectional view of the joint between the column 261 and the beam 263 on which the connecting reinforcements 269b, etc. are disposed.
- the beltlike reinforcements 271a and 271b are disposed on the connecting reinforcement 269b in a winding condition.
- the column 261 or the beam 263 and the sheetlike connecting reinforcement 269b are bonded such that tension is mutually transmitted via shear resistance of a bond zone.
- the connecting reinforcement 269b and the beltlike reinforcements 271a and 271b are bonded the following combinations: the connecting reinforcement 269b and the beltlike reinforcements 271a and 271b; the column 261 or the beam 263 and the connecting reinforcement 269a; and the connecting reinforcement 269a and the beltlike reinforcements 271a and 271b.
- a reinforcement 273a is wound about the exterior of the column 261, and a reinforcement 273b is wound about the exterior of the beam 263.
- the reinforcements 273a and 273b are stretchable sheetlike or beltlike materials.
- the connecting reinforcements 269a and 269b are disposed on the joint between the column 261 and the beam 263 so as to enhance a member-to-member reinforcement effect. Furthermore, the beltlike reinforcement 271a is cross-wound onto a joint of a bigger member, i. e., about a joint of the column 261, and the beltlike reinforcements 271a and 271b are wound about the exterior of the column 261 and that of the beam 263 in layers, to thereby obtain a required amount of reinforcement.
- the reinforcement is cross-wound onto the joint.
- the reinforcement can be wound about the joint in the form of the letter T or the like.
- Reinforcement is applicable not only to the joint between a column and a beam but also to the joint between other members.
- the method can be combined with the method using slits or bores. This combined method is particularly effective for reinforcing the joint between members of greatly different thicknesses or shapes, such as the joint between a slab and a beam or the joint between a wall and a beam.
- the connecting reinforcements 269a and 269b can be omitted.
- the reinforcing member is made of a material having high ductility and high bendability, or extensibility, and installed on the surface of or inside a structure member or substrate through the fixation using an adhesive, so as to constrain the apparent volume expansion of the structure member to control the change in shape or the damage of the structure member.
- a material which is inexpensive and facilitates working and bonding such as a polyester sheet, is used as a reinforcement material.
- the Young's modulus of such a material is about one-tenth that of concrete or one-hundredth that of iron.
- the reinforcement material's effect of bearing part of a load imposed on a member during the elastic stage accompanied by very small strain as do reinforcing bars of reinforced concrete is very weak; specifically, as weak as the above-mentioned Young's modulus ratios.
- the reinforced member absorbs very large energy in the above-mentioned sequential repeated-deformation process while maintaining rigidity, thereby preventing the collapse of a structure which would otherwise result from reception of an abrupt external force, such as a seismic force.
- FIG. 41 is a diagram showing the relationship between cumulative deformation and hysteretic absorbed energy with respect to a reinforced member on which a repeated load is imposed.
- the horizontal axis represents cumulative deformation
- the vertical axis represents hysteretic absorbed energy.
- a certain limit (called a shape retainment limit energy 275) is present according to the type and amount of material. When this limit is exceeded, a material behaves in a granular fashion, and thus the shape of a member begins to vary significantly.
- a member reinforced according to a method of the present invention or the previous application is deformed such that the cross section assumes a circular shape, and the entire shape approaches to the shape of linked balls. Accordingly, the shape of a structure also varies significantly.
- the method of the present application is characterized by being able to cope with a wide energy region and a wide deformation region, and an enhancement of an effect to be yielded as shown in FIG. 41.
- the seismic isolator can absorb energy in such an amount that a material having a volume equivalent to that of the seismic isolator is pulverized substantially completely, while variation in shape is minimized, and rigidity is retained. This is a very efficient behavior for a seismic isolator.
- the filler When a special filler is mixed into a component material of a seismic isolator, the filler functions to internally reinforce the material through utilization of energy, such as heat, to be generated by work which is done by an external force in the above-mentioned process, thereby further enhancing a seismic isolation effect.
- FIG. 42 is a graph showing the relationship between tensile stress and strain with respect to a reinforcement material impregnated with resin and a reinforcement material unimpregnated with resin.
- the vertical axis represents tension
- the horizontal axis represents extensional strain (%).
- An impregnated-with-resin curve 277 shows the stress-strain relation obtained from a tensile test which was conducted on a polyester sheetlike textile impregnated with epoxy resin after the resin was cured.
- An unimpregnated-with-resin curve 279 shows the stress-strain relation obtained from a tensile test which was conducted on the same sheetlike textile unimpregnated with epoxy resin.
- the test results shown in FIG. 42 show the following: as a result of a sheet or beltlike material woven from polyester fiber being impregnated with resin, resin yields the effect of restraining deformation of fiber for the range of small strain; thus, the material represented by the impregnated-with-resin curve 277 exhibits increased rigidity as compared with the material represented by the unimpregnated-with-resin curve 279.
- the material represented by the impregnated-with-resin curve 277 loses the above-mentioned effect without significant breakage of fiber. As a result, deformation can be maintained until a large strain of not less than 15% is reached.
- a reinforcement material impregnated with resin i.e., a material of a single kind, enhances the effect of restraining deformation for the range of small strain as well as yields the effect of bearing a load for the range of large strain.
- the aforementioned reinforcing member can be designed as follows.
- the dynamic property (the relationship between external force and deformation) of the reinforced structure is defined by the following parameters.
- the reinforced structure can be designed by calculating the performance of a structural body subject to reinforcement, according to these parameters and data of the structural body.
- Thickness of reinforcing member t 2) Young's modulus of reinforcing member E f 3) Fracture strain of reinforcing member ⁇ fb 4) Reinforcing-member stress at yield of fixation structure ⁇ fmax 5) Reinforcing-member installation mode (Whether reinforcing-member is closingly looped (FIG. 1) or not (FIG.
- the gap width and reinforcing-member tensile force in a SRF-reinforced structure has a relationship as shown in FIG. 44. Specifically, if the gap width is increased from zero, a reinforcing member will be elongated in a fixation zone, and thereby a reinforcing-member stress will be generate. When the elongation of the reinforcing member on the gap reaches ⁇ 1, the release of the fixation structure is initiated to generate a free length a (FIG. 44).
- the fixation force will be maintained to increase a reinforcing-member tensile force in proportion to the gap width until the reinforcing member reaches a fracture stress (stress corresponding to the fracture strain ⁇ fb ) (range from Point C to Point D).
- the relationship between reinforcing-member tensile force and restoring force can be determined from the theory as shown in the expressions [9] and [10], or an experimental test.
- the reinforcing-member elongation ⁇ 1 providing the maximum value of the reinforcing-member tensile force is a value derived from integrating strains in the fixation zone of the reinforcing member at the time of the limit where the bonding is released (when the reinforcing-member tensile force reaches ⁇ fmax ), and becomes smaller as the Young's modulus of the reinforcing member is increased. This factor is ignored in the theory shown in the expressions [1] to [4].
- the boundary-surface peeling energy is defined as energy required for peeling the bonding boundary-surface of unit area between a thin elastic body and a substrate as shown in FIG. 44, and can be calculated from the following expression [102] using the maximum tensile force ⁇ fmax caused in the elastic body and the thickness t and Young's modulus of the elastic body, which are obtained as the result of a peeling test.
- G f t 2 E f ⁇ 2 f max
- the expression [101] is obtained by resolving the formula [102] about ⁇ fmax .
- a conventional design formula for reinforced concrete structure members can be applied to the calculation of the reinforcement effect of a SRF reinforcing member by substituting the SRF reinforcing member with a reinforcing bar and calculating the reinforcement effect using the boundary-surface peeling energy etc. by use of the phenomenon that a SRF reinforcing member apparently yields at ⁇ fmax as shown in FIG. 55 (expression [103]).
- the gap width in the design limit state does not reach the peeling-limit elongation ⁇ 1 illustrated in FIGS. 44 and 55 due to a small Young's modulus of the SRF reinforcing member as compared to that of reinforcing bar.
- the above apparent yield stress ( ⁇ fmax in the expressions [101] and [102]) is a maximum stress capable of being borne before the fixation of the reinforcing member is released (FIG. 45), and calculated from the Young's modulus of the reinforcing member, the boundary-surface peeling energy and the thickness of the reinforcing member using the expression [101].
- the apparent yield stress is reduced in reverse proportion to the square root of the thickness.
- the reinforcing-member thickness can be determined by a simple repeated calculation.
- the present invention can provide a reinforcing material or member excellent in ductility and load-withstanding capacity, quickly at a low cost.
- the effects of the reinforcing member according to the present invention is effective to repair, maintenance and reinforcement of existing structure bodies, and usable in new structural bodies. In either case, the cost, construction period etc. required for satisfying a desired performance can be reduced as compared to those in conventional techniques.
- the reinforcing material or member according to the present invention is useable as a safeguard against sudden external forces such as explosion, which have been untreatable by conventional techniques.
- the reinforcing member installed on the outer surface of a structure member as a primary element thereof makes it possible to provide a reinforced structure readily at a low cost and achieve enhanced reinforcement performance.
- the present invention facilitates reuse of decrepit or affected structural bodies to promote effective use of existing structural bodies and industrial resources and to allow industrial wastes to be reduced.
- a reinforcement configuration, a seismic isolator, and a reinforcement method for a structure according to the present invention can suitably be applied to, for example, the following cases: a member to be reinforced involves undulation or an irregular profile; a member is joined to or located in proximity to another member or a nonstructural member; a reinforcement is possibly deteriorated due to interaction between a member and the reinforcement or between the reinforcement and an external environment; a reinforcement effect must encompass a small deformation through a large deformation; and seismically isolating reinforcement is required.
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Abstract
Disclosed is a reinforcing member, which comprises a woven body formed by a
weaving process, or a tape-shaped or sheet-shaped body, having a high ductility
and high bendability. The reinforcing member is adapted to be installed on a
surface of a structure member or a boundary portion of the structure member, or
inside a structure member, to reinforce the structure member. The woven body, or
a tape-shaped or sheet-shaped body, has a Young's modulus equal to or less than
that of the structure member, and a tensile fracture strain of 10% or more. The
Young's modulus of the reinforcing member is preferably in the range of 1/2 to 1/20,
more preferably 1/5 to 1/10, of that of the structure member. Specifically, the
Young's modulus of the woven body is preferably in the range of 500 to 50000 MPa,
more preferably 1000 to 10000 MPa. The present invention also provides a
reinforced structure using the above reinforcing member.
Description
The present invention relates to a reinforcing member for a structural body, a
reinforced structure using the reinforcing member, and a method for designing the
reinforcing member.
Heretofore, there have been known various techniques (reinforced structures,
reinforcing members and reinforcing methods) for reinforcing a member of a
structural body (hereinafter referred to as "structure member"). Among them, a
conventional technique characterized by installing a reinforcing member on the
surface of or inside a structure member subject to reinforcement includes (1) a
technique of embedding a reinforcing bar in concrete as a substrate, or so-called
reinforced concrete technique, (2) a technique of driving a bolt or nail into a
substrate, (3) a technique of incorporating a high-strength steel rod inside concrete
as a substrate and introducing a tensile force to the steel rod, (4) a technique of
wrapping a steel plate around a structure member, or so-called steel-plate wrapping
technique, and (5) a technique of using a so-called continuous-fiber reinforcing
member made of carbon or aramid fibers and resin, such as epoxy resin,
impregnated therein.
Another conventional technique characterized by installing a reinforcing
member between the respective outer surfaces of adjacent structure members
includes (6) a technique of forming a space, such as hole or slit, in the structure
members, and penetratingly inserting a reinforcing member into the space, and (7)
a technique of forming a space in the structure members, penetratingly inserting
bundled fibers of a continuous-fiber reinforcing member into the space, and then
spreading out the fibers.
Still another conventional technique characterized by installing a reinforcing
member on the surface of a flat structure member, such as wall, includes (8) a
technique of constraining a reinforcing member by a metal plate formed with a hole,
and a bar, such as a metal bar, penetrating the structure member, and (9) a
technique of bundling the fibers of a continuous-fiber reinforcing member at the
edge of the structure member, and anchoring the bundled fibers to the edge of the
structure member or another member adjacent to the structure member.
Yet another conventional technique characterized by forming a reinforcing
member in a cylindrical shape and filling the inner space of the cylindrical
reinforcing member with filler includes (10) a technique of forming an iron
reinforcing member in a cylindrical shape, and filling the inner space of the
cylindrical reinforcing member with concrete to use the obtained reinforcing
member as a column.
Yet still another conventional technique characterized by installing a plurality of
reinforcing members on the outer surface of a structure member in a superimposed
manner includes (11) a technique of providing a plurality of continuous-fiber
reinforcing members on the outer surface of a structure member in its vertical and
horizontal directions in a superimposed manner.
Another further conventional technique characterized by providing a
strip-shaped reinforcing member on the outer surface of a structure member
includes (12) a technique of providing a strip-shaped (tape-shaped) steel plate or
continuous-fiber reinforcing member around a structure member, (13) a technique
of filling epoxy resin along a crack of a substrate in a strip shape, and (14) a
technique of fixing a strip-shaped steel plate on the surface of a structure member
by use of epoxy resin or an anchor bolt.
Still a further conventional technique characterized by installing a reinforcing
member on the outer surface of a junction of structure members includes (15) a
technique of providing a steel jacket or attaching a continuous-fiber reinforcing
member on the outer surface of a junction of structure members.
An additional conventional technique characterized by using a
resin-impregnated reinforcing member includes (16) a technique of using a
so-called continuous-fiber reinforcing member made of carbon or aramid fibers and
epoxy resin impregnated therein.
The above techniques (4) to (14) are intended to transmit a shear stress
directly to a reinforcing member without causing any displacement or peeling
between a substrate and the reinforcing member. For example, the shear
reinforcement effect of a reinforced concrete member is said to have the same
mechanism as that of a shear-reinforcing bar, and the reinforced concrete member
is designed by assigning a reinforcement amount and coefficients expressing the
property and reinforcement effect of a reinforcing member to a design formula of the
shear-reinforcing bar. Most of the techniques (3) and (15) also include the step of
injecting a grouting or resin material between a reinforcing member and a substrate
to transmit a shear stress directly to the reinforcing member. The term "substrate"
herein means a material constituting a structure member, and a physical object to
which a reinforcing member is to be fixed.
Therefore, an intended reinforcement effect can be obtained only if a substrate
is maintained in its proper state, and no displacement or peeling is caused between
the substrate and the reinforcing member. This prerequisite must be guaranteed
by the design technique and construction management.
The reinforcing member, such as the reinforcing bar, the steel rod and the steel
plate, used in the techniques (1) to (4), (6), (8), (10), (12), (14) and (15), has the
flexural rigidity and shear rigidity of its own. Thus, if a substrate is locally subjected
to a large strain, the reinforcing member cannot follow the local strain, resulting in
loss of the reinforcement effect due to the occurrence of local fracture in the
substrate or local buckling or cracks in the reinforcing member.
In the techniques (12) and (16), the reinforcing member made of
resin-impregnated continuous fibers has the same problem as described above due
to the flexural and shear rigidities resulting from the effect of resin impregnation in
addition to the flexural and shear rigidities of the continuous fibers themselves.
Further, while this reinforcing member is designed using a formula based on the
assumption that it has only tensile rigidity, an intended reinforcement effect is
actually likely to be lost due to occurrence of bending or local buckling in
consequence of the flexural rigidity and shear rigidity of its own.
The material, such as carbon or aramid fibers, used in the techniques (5), (7),
(11) and (16), has a fracture strain of 2% to several %, which is liable to cause
damages by the comers of a substrate or the unevenness of the surface of a
substrate. Thus, an appropriate construction management is essentially required.
Further, if the substrate has some cracks due to a certain external force, the
reinforcing member will be locally broken, which leads to significant deterioration or
disappearance of the reinforcement effect.
In the techniques (1) to (15), if a structure member contacting with another
structure member or having a flat shape or a concavo-convex or irregular surface is
reinforced by forming a through-hole therein and penetratingly inserting a
reinforcing member into the through-hole, such a construction work will involve a
problem of high cost and/or extended period, and a particular technology or tool will
be required to fix the edge of the reinforcing member or insert the reinforcing
member.
In the above technique, a plate, a rod or a bundle of continuous fibers which
serves as an anchor portion of the reinforcing member (hereinafter referred to as
"anchor member") has a structure and rigidity different from those of the remaining
portion of the reinforcing member. Thus, the threshold value of the reinforcement
effect is undesirably defined by the threshold values of stress transmission between
the reinforcing and anchor members and between the anchor member and the
substrate.
Further, the substrate is requited to bear the stress occurring at the fixed
portion of the anchor member. Therefore, if the strength of the substrate is
lowered due to aged deterioration or such an aged deterioration is calculated, the
above technique cannot be applied.
In the technique of introducing a tensile force to a steel rod, if it is applied to a
substrate exhibiting significant creep, such as concrete, the tensile force of the steel
rod will be reduced due to the creep, and the reinforcement effect will be lost across
the ages. Further, if the anchor portion of the steel rod is broken by a sudden
external force due to earthquake or the like, the steel rod suddenly freed from the
tensile force will be likely to jump out of the concrete and damage the surroundings.
Thus, the techniques (1) to (16) are required to install the reinforcing member
by spending an extended time in association with professional engineers, which
involves a high construction cost. The application of these techniques is also
limited to a specific substrate which can be formed to have a smooth surface as in
reinforced concrete, and allows a reinforcing member to be brought into close
contact therewith so as to form a structure capable of locally transmitting a shear
force.
In the so-called continuous-fiber reinforcing member composed of epoxy-resin-impregnated
carbon or aramid fibers in the technique (16), material constants, such
as strength and Young's modulus, important in reinforcement design are defined in
the state after the fibers are impregnated with the resin. This reinforcing member
is fixed to a structural body, for example, according to the following process as
disclosed in Japanese Patent Laid-Open Publication No. 8-260715.
The reinforcing member is fixed through the many steps as described above,
and the adhesive in the step (v) can be applied only after the adhesive applied in
the step (iii) is completely cured or hardened by chemical action (if the adhesive in
the step (v) is prematurely applied, gas bubbles generated during the chemical
action will be confined in the reinforcing member to cause the deterioration in
strength of the reinforcing member. Thus, the above process has to be completed
by taking a great number of days.
The impregnating step has to be carried out in the working site under a strict
construction management. If an external force acts to cause the peeling between
the resin and the continuous fibers, or the resin is defective in curing or deteriorated
due to environmental conditions, the design performance of the reinforcing member
will be significantly degraded.
Generally, if a structure member has a non-flat or irregular surface, such as a
wall-mounted column, or is joined to or located very close to another member or
non-structural material, such as a column having a window frame attached thereto,
it is difficult to obtain a sufficient reinforcement effect. Further, the interactions
between a structure member and a reinforcing member and between the reinforcing
member and the surrounding are likely to cause deterioration of the reinforcing
member. Furthermore, there is the need for obtaining a sufficient reinforcement
effect in a wide range from a small deformation to a large deformation.
According to a first aspect of the present invention, there is provided a
reinforcing member comprising a woven body formed by a weaving process to have
a high ductility and high bendability. The reinforcing member is adapted to be
installed on a surface of or inside a structure member to reinforce the structure
member. The woven body has a Young's modulus equal to or less than that of the
structure member, and a tensile fracture strain of 10% or more.
In the reinforcing member set forth in the first aspect of the present invention,
the Young's modulus of the woven body may be in the range of 1/2 to 1/20,
preferably 1/5 to 1/10, of that of the structure member. Specifically, the Young's
modulus of the woven body may be in the range of 500 to 50000 MPa, preferably
1000 to 10000 MPa.
The woven body may have a thickness in the range of 0.2 to 20 mm, preferably
0.5 to 15 mm, more preferably 1 to 10 mm.
The woven body may include yarns made of polyester.
The woven body may have a bending deformation angle of 90-degree or more,
and a shear deformation angle of 2-degree or more.
The reinforcing member set forth in the first aspect of the present invention
may be heat-set to allow a Young's modulus in a limit state to be greater than a
Young's modulus immediately before fracture. The heat setting process comprises
the steps of heating the reinforcing member to apply a tensile force thereto, and
then cooling the reinforcing member while maintaining the tensile force, so as to
provide enhanced initial rigidity and Young's modulus to the reinforcing member.
In addition, a resin impregnation process may be performed to impregnate the
reinforcing member with resin.
This reinforcing member may have an elongation strain in the range of 0.1 % to
10% in the limit state.
According to a second aspect of the present invention, there is provided a
reinforcing member comprising a tape-shaped or sheet-shaped body made of a
rubber-based or resin-based elastic material having a high ductility and high
bendability. The reinforcing member is adapted to be installed on a surface of or
inside a structure member to reinforce the structure member. The tape-shaped or
sheet-shaped body has a Young's modulus equal to or less than that of the
structure member, and a tensile fracture strain of 10% or more.
In the reinforcing member set forth in the second aspect of the present
invention, the Young's modulus of the tape-shaped or sheet-shaped body may be in
the range of 1/2 to 1/20, preferably 1/5 to 1/10, of that of the structure member.
Specifically, the Young's modulus of the tape-shaped or sheet-shaped body may be
in the range of 500 to 50000 MPa, preferably 1000 to 10000 MPa.
The tape-shaped or sheet-shaped body may have a thickness in the range of
0.2 to 20 mm, preferably 0.5 to 15 mm, more preferably 1 to 10 mm.
The tape-shaped or sheet-shaped body may have a bending deformation
angle of 90-degree or more, and a shear deformation angle of 2-degree or more.
As long as meeting the aforementioned requirement, the reinforcing member
set forth in the second aspect of the present invention may be formed by spraying
or applying a rubber-based or resin-based material or fiber-reinforced mortar to the
structure member in the working site. While the material cost in this case is higher
than the polyester woven fabric, it is often the case that such a reinforcing member
is advantageous in terms of the ratio of reinforcement effect to cost as compared to
conventional techniques. A Young's modulus in a limit state such as a design
ultimate state, a fracture strain and a fracture stress can be calculated based on the
stress-strain relationship of the reinforcing member to determine a required
reinforcement amount (the thickness of the reinforcing member) and the
performance of the structure member according to an after-mentioned calculation
method.
According to third and fourth aspects of the present invention, there are
provided two types of reinforced structures for a structural body. The reinforced
structures comprise the reinforcing members set forth in the first and second
aspects of the present invention, respectively. In these reinforced structures, the
reinforcing member is fixed on a surface of or inside a substrate which constitutes a
structure member of the structural body and consists of at least one material, or on
a surface of a boundary portion of the structure member or inside the structure
member, to reinforce the structure member.
In the reinforced structures set forth in third and fourth aspects of the present
invention, the reinforcing member may be fixed to the structure member in such a
manner that an effective constraint range of the reinforcing member covers the
pre-calculated width and length of a gap to be generated in the structure member in
future.
The substrate may be made of at least one material selected from the group
consisting of (1) concrete, (2) steel frame, (3) brick, (4) block, (5) gypsum board or
plaster board, (6) wood, (7) rock, (8) earth or soil, (9) sand, (10) resin and (11)
metal.
The fixation may be performed by means of an adhesive. The layer of the
adhesive applied to the reinforcing member or the structure member may have a
thickness in the range of 5 to 90%, preferably 20 to 40%, of the thickness of the
reinforcing member.
The fixation may be performed by placing the reinforcing member on the
structure member through the layer of the adhesive and then applying a pressing
force or a beating force to the reinforcing member while allowing a part of the
adhesive to be infiltrated into the reinforcing member. In case of the woven body,
the fixed portion of the reinforcing member may have a void ratio of 1.1 or more. In
case of the tape-shaped or sheet-shaped body, the fixed portion of the reinforcing
member may have a void ratio of 1.4 or more.
The bonding strength of the fixation may be less than the peeling/shear
fracture strength between the structure member and the reinforcing member. This
prevents the reinforcement effect from disappearing due to fracture in the structure
member and the reinforcing member before the occurrence of peeling in the fixed
portion. Specifically, the bonding strength may be in the range of 10 to 80% of
peeling/shear fracture strength in the surface of the structure member applied with
the adhesive.
The adhesive may be a one-component, non-solvent adhesive.
The fixation of the reinforcing member to the structure member may be
performed without chamfering the structure member and adjusting the unevenness
of the surface of the structure member.
In the reinforced structures set forth in third and fourth aspects of the present
invention, even after the structure member has a gap, the reinforcing member holds
or constrains the structure member in such a manner that it forms an envelope
surface covering a surface of the structure member adjacent to the gap to serve as
a medium for transmitting a stress acting on the structure member on both sides of
the gap (bridge for transmitting the stress). The envelope surface serving as the
transmission medium is formed by elongation in the reinforcing member adjacent to
the gap and/or peeling in the fixed portion adjacent to the gap. In other words, the
envelope surface serving as the transmission medium is formed by the elastic
elongation of the reinforcing member in a free zone where the fixation is released
due to the generation of the gap.
The term "substrate" means a material constitutes a structure member subject
to reinforcement, and a physical object to which a reinforcing member is to be fixed.
The shape and material of the substrate are appropriately selected depending on a
desired performance or function of the structure member. The material of the
substrate is not limited to a specific form or type, and may be any conventional
structural material, any conventional non-structural material or any filler material.
For example, the substrate may be concrete, steel frame, brick, block, gypsum or
plaster board, precast concrete, wood, rock, earth or soil, sand, metal, or granular
resin. The substrate may include plural kinds of materials. For example, when a
filler material such as resin is filled in a space between a structure member and a
reinforcing member, the combination of the filler material and the material of the
structure member may be defined as the substrate.
The term "gap" herein means a chap or crack generated in a structure member.
When a structure member has a deformation inducing a gap therein, the resulting
displacement between the structure member and a reinforcing member adjacent to
the gap forms an envelope surface in a portion of the reinforcing member around
the gap of the structure member without any fracture of the reinforcing member.
The enveloped surface serves as a bridge allowing a stress of the structure
member to be transmitted across the gap. That is, a shear stress is transmitted
through the boundary surface between the reinforcing member and a portion of the
structure member having no gap or through a fixed portion. The envelope surface
of the reinforcing member is formed based on a plurality of factors including as the
elongation of the reinforcing member adjacent to the gap, the release (peeling or
another factor) of the fixation adjacent to the gap, and the fixation around the gap.
The fixation of a reinforcing member to a structure member is performed by
applying an adhesive a part or all of the boundary surface between the structure
member and the reinforcing member, or by closingly looping a reinforcing members
in an adhesive or mechanical manner while enclosing and deforming a portion of
the structure member, so as to provide a tensile force in the reinforcing members to
generate a frictional or bearing force between the reinforcing member and the
structure members.
The adhesive to be applied to the boundary between a structure member and
a reinforcing member is required to maintain an adhesion strength required for
fixing the reinforcing member to the structure member, for the period of use of the
structure member under environmental conditions of the structure member. In this
case, there is no need to set the required adhesion strength at a value higher than
the fracture strength of the structure member or the reinforcing member. Thus, the
adhesive may be one-component adhesive. The adhesive may also be applied to
the reinforcing member in advance, and stored together with the reinforcing
member. In this case, an operation of fixing the reinforcing member can be quickly
completed.
The term "fixation zone" herein means a zone where the reinforcing member is
fixed. The term "free zone" means a zone where the fixation of the reinforcing
member is released (due to peeling or another factor). In an after-mentioned
design method, the ratio of the size of the fixation zone to the size of the free zone is
expressed by a numerical value of "constraint ratio".
The terms "fixation strength" and "fixation range" herein mean a strength and a
range capable of causing the displacement in a specific finite areas (free zone) of
reinforcing and structure members when the structure member has a local fracture
inducing a gap, so as to allow a stress of the structure member to be transmitted
through the reinforcing member across the gap without any fracture of the
reinforcing member.
The relationship between load and deformation of the structure member after
the generation of the gap is expressed as the functions of the dimensions of the
structure member, the boundary condition of the structure member, the position and
size of the gap, the Young's modulus and thickness of the reinforcing member, and
the size of a free zone caused by the gap. Thus, a required strength, required
Young's modulus, required amount (required installation range, required thickness
etc.) and required fixation strength of the reinforcing member can be calculated
based on a value in a limit state (tolerance or threshold value) of the size (width
etc.) of a gap to be generated in the structure member, the size of a zone where the
elongation of the reinforcing member can be neglected (fixation zone), and the size
of a zone where the reinforcing member is to be elongated (free zone).
A Young's modulus for use in the calculation of the required amount etc. of the
reinforcing member is a value (limit state value) corresponding to a strain to be
generated in the reinforcing member in a limit state where the size of the gap
reaches the threshold value. Therefore, in view of the elastic property of the
reinforcing member, the design of setting a Young's modulus in the limit state to be
greater than a Young's modulus corresponding to another strain such as a strain
immediately before fracture can advantageously reduce the reinforcement amount.
The installation range of the reinforcing member is not necessarily the entire
surface of the structure member, but may be a portion of the structure member. In
this case, the reinforcing member is installed to form an envelope surface in the
circumferential direction of the structure member or to form a surface capable of
being in contact with the portion of the surface of the structure member smoothly
from the outside.
The installation range of the reinforcing member is selectively determined
depending on a desired performance, shape or configuration of a structure member,
or a method of fixing a reinforcing member. For example, if a plurality of structure
members are located adjacent to each other, the reinforcing member may be
installed such that an envelope surface is formed to cover the junction between the
adjacent structure members, or it is penetratingly inserted into a hole or slit formed
in the adjacent structure members. Further, if the structure member is a flat
member such as a wall, a reinforcing member may be installed on only one of the
opposite surfaces thereof, or a reinforcing member may be installed on the
respective opposite surfaces thereof and closingly looped through a through-hole
formed in the structure member.
The aforementioned reinforced structure may be formed by providing a
reinforcing member to a structure member of an existing structural body, or may be
formed by installing a reinforcing member to a structure member of a structural body
to be newly constructed. When the reinforced structure is applied to a new
structural body, the size and weight of the structure member can be reduced as
compared to the conventional techniques to provide reduced seismic load. This
makes it possible to achieve drastically reduced construction cost of the structural
body, and significantly enlarged utilizable space of a living room or the like.
With reference to the drawings, various embodiment of the present invention
will now be described in detail.
FIG. 1 is a perspective view of a structure member (or a member of a structural
body) with a reinforcement member according to an embodiment of the present
invention. FIG 2 is a sectional view taken along the line A-A in FIG. 1.
As shown in FIGS. 1 to 3, a structure member 1 comprises a substrate 3 with a
reinforcing member 5. The reinforcing member 5 is installed, for example, in such
a manner that it envelops a portion of the surface of the substrate 3 (see FIG. 1), or
it encloses a given portion (periphery etc.) of the substrate (FIG 3).
The substrate 3 is principally a material constituting the structure member 1
subject to reinforcement, and a physical object to which the reinforcing member 5 is
to be fixed. The shape and material of the substrate 3 are appropriately selected
depending on a desired performance or function of the structure member 1. The
substrate 3 is a structural material such as reinforced concrete, a non-structural
material such as block or brick, or a filler material such as sand or granular resin.
The reinforcing member 5 installed on the surface the substrate 3 acts to bear
a stress of the substrate 3 while bridging between both sides of a fractured surface
such as chap or crack (or gap) generated in the substrate.
In addition to the above function, a reinforcing member 5 according to a first
mode of embodiment is composed of a woven body having all of extensibility (high
ductility and high bendability), strength and elasticity, and adapted to be installed on
the surface of or inside a substrate of a structural body to reinforce the substrate.
The woven body characteristically has a Young's modulus equal to or less than that
of the structure member (substrate), and a tensile fracture strain of 10% or more.
When the structure member includes plural kinds of primary substrates
(materials), the term "Young's modulus of the structure member (substrate)" herein
means the lowest one in the respective Young's moduluses of the materials.
As above, the reinforcing member has high ductility and high bendability, or
extensibility. The term "high ductility" means to have a large fracture strain. The
term "high bendability" means to readily cause a large bending deformation and
shear deformation (high flexibility) without fracture.
Even if a substrate is deformed to have a gap or irregular surface, the
reinforcing member having high ductility can constrain the substrate without fracture
to maintain a desired reinforcement effect.
The reinforcing member having high bendability can be readily bent at an
acute angle. Thus, the reinforcement can be installed along an irregular
circumferential surface of a structure member, and can be deformed under load to
have a fixed portion formed in conformity to the curvature or corner angle of a
substrate.
The reinforcing member is required to have elasticity for generating a tensile
force in response to change in the circumferential length of a substrate to bring out
a geometrical constraint effect and coping with a repeated alternate load or the like.
Preferably, the rigidity of the reinforcing member is greater at the initial stage of the
generation of strain than immediately before fracture.
In the present invention, the Young's modulus of the woven body constituting
the reinforcing member 5 is set to be equal to or less that that of the structure
member. This is intended to reduce a stress acting on the boundary surface the
reinforcing member and the substrate 3 when the reinforcing member starts
deforming in response to the occurrence of deformation or crack in the structure
member 1 due to a load acting on the substrate 3, so as to increase a limit
deformation causing peeling in the boundary surface. Further, the tensile fracture
strain of the woven body is set at 10% or more. Because in the design of structural
bodies for an accidental load due to earthquake or the like, a design limit is
generally about 2 to 4% of deformation in a structure member. Additionally
considering a local-strain-concentration coefficient of 5, the reinforcing member
would be not fractured in the design limit if the fracture strain is 10% or more.
According to the results of loading tests of a structure member, in case where a
reinforcing member including aramid fibers having several % of fracture strain was
bonded on a surface of a structure member, the fracture of the reinforcing member
was observed. On the other hand, in case where the structure member was
reinforced by a SRF reinforcing member having 10% or more of fracture strain, no
fracture was observed in the reinforcing member
By contrast, in the reinforcing member disclosed in the aforementioned
Japanese Patent Laid-Open Publication No. 8-260715, the Young's modulus and
fracture strain of aromatic polyamide fibers used therein are directly applicable.
Thus, the Young's modulus is in the range of 80000 to 120000 MPa, and the tensile
fracture strain is in the range of 2.5 to 4.5%. Further, when the aromatic polyamide
fibers act as an actual reinforcing member, it will be an
aromatic-polyamide-fiber-reinforced epoxy resin having higher bending and shear
rigidities than those of the elemental fibers. As a result, the reinforcing member is
likely to peel off over a wide range at the same time due to inability of following the
deformation of a substrate. In this connection, the Young's modulus of concrete is
about 20000 MPa, and the Young's modulus of hard wood such as oak is about
10000 MPa.
The Young's modulus of the woven body is preferably in the range of 1/2 to
1/20, more preferably 1/5 to 1/10, of that of the substrate. If the Young's modulus
is less than the lower limit of the range (or the value of Young's modulus is
excessively small), the reinforcing member has to be designed to have an
increased thickness to obtain a desired reinforcement amount. This is
economically inefficient. Further, as described later, a peeling-limit elongation (δ1:
FIGS. 44 and 45) is increased, resulting in delayed response of the reinforcement
effect and increased damage of the structure member.
Specifically, the Young's modulus of the reinforcing member is preferably in the
range of about 500 to 5000 MPa, more preferably about 1000 to 1000 MPa.
Preferably, the tensile fracture strength of the woven body is in the range of 3
to 5 times of that of the structure member. Any local fracture of the structure
member can be avoided by setting a stress concentration coefficient in the range of
3 to 5.
The thickness of the woven body is preferably in the range of 0.2 to 20 mm,
more preferably 0.5 to 15 mm, particularly 1 to 10 mm. This range is desired to
obtain an intended performance and facilitate handling.
Preferably, the material of strings constituting the woven body is polyester
(fiber).
Preferably, the woven body has a bending deformation angle of 90-degree or
more, and a shear deformation angle of 2-degree or more.
Preferably, the woven body is heat-set to allow a Young's modulus in a limit
state to be greater than a Young's modulus immediately before fracture.
Preferably, the reinforcing member has an elongation strain in the range of
0.1% to 10% in the limit state.
A reinforcing member according to a second mode of embodiment is a
tape-shape or sheet-shaped body made of a rubber-based or resin-based elastic
material, and adapted to be installed on a surface of or inside a substrate of a
structural body to reinforce the substrate. Further, the tape-shaped or
sheet-shaped body has a Young's modulus equal to or less than that of the
structure member, and a tensile fracture strain of 10% or more.
The Young's modulus of the tape-shaped or sheet-shaped body is preferably in
the range of 1/2 to 1/20, more preferably 1/5 to 1/10, of that of the substrate.
Specifically, the Young's modulus of the reinforcing member composed of the
tape-shaped or sheet-shaped body is also preferably in the range of about 500 to
5000 MPa, more preferably about 1000 to 1000 MPa.
The thickness of the tape-shaped or sheet-shaped body is preferably in the
range of 0.2 to 20 mm, more preferably 0.5 to 15 mm, particularly 1 to 10 mm.
Preferably, the tape-shaped or sheet-shaped body has a bending deformation
angle of 90-degree or more, and a shear deformation angle of 2-degree or more.
The above factors of the reinforcing member according to the second mode of
embodiment have been selectively determined in the same way as that in the
reinforcing member according to the first mode of embodiment.
Two types of reinforced structures for a structural body according to third and
fourth modes embodiment of the present invention comprise the reinforcing
members according to the first and second modes of embodiment, respectively.
Further, the reinforcing member is fixed on a surface of or inside a substrate
constituting a structure member and including at least one material to reinforce the
substrate.
In the reinforced structures, the reinforcing member is preferably fixed to the
substrate in such a manner that an effective constraint range of the reinforcing
member covers the pre-calculated width and length of a gap to be generated in the
substrate in future.
In other words, the reinforcing member 5 is fixed to the substrate 3 in the
structure member 1. More specifically, the reinforcing member 5 and the substrate
3 are constrained to one another. The mechanism of this constraint is roughly
classified into two types. A first mechanism is a bonding constraint, and a second
mechanism is a geometrical constraint.
The first mechanism or bonding constraint is achieved by bonding the
reinforcing member 5 to the substrate 3. In this case, even after a gap is generate
to create a zone where the bond is separate (herein after referred to as "free zone"),
as long as a bonded portion exists around the free zone, the bonding constraint can
be maintained.
The thickness of the layer of an adhesive applied to the reinforcing member or
the substrate is preferably in the range of 5 to 90%, more preferably 20 to 40%, of
the thickness of the reinforcing member.
The fixation is performed by placing the reinforcing member on the substrate
through the layer of the adhesive and then applying a pressing force or a beating
force to the reinforcing member while allowing a part of the adhesive to be infiltrated
into the reinforcing member. In case of the woven body, the fixed portion of the
reinforcing member preferably has a void ratio of 1.1 or more. In case of the
tape-shaped or sheet-shaped body, the fixed portion of the reinforcing member
preferably has a void ratio of 1.4 or more. In this way, gas generated during the
curing reaction of the adhesive can be adequately released from the adhesive layer
or the reinforcing member. Thus, an initial bonding ability can be achieved without
generation of gas bubbles in the adhesive layer, defective bonding, and
swollenness and float of the adhesive layer. The upper limit of the void ratio is not
limited to a specific value, but preferably in the range of about 2 to 3.
Preferably, the bonding strength is less than the strength of the substrate. If
the bonding strength is equal to or greater than the strength of the substrate, the
fracture of the structure member causes the generation of a tensile force in the
reinforcing member and the release of the bonding to annul the reinforcement effect
in a wide range at the same time. The bonding strength is preferably in the range
of 10 to 80% of peeling/shear fracture strength in the surface of the substrate
applied with the adhesive. If the bonding strength is higher than the upper limit of
the range, the structure member will be damaged in an operation of detaching the
reinforcement. If the bonding strength is lower than the lower limit of the range, a
desired reinforcement effect cannot be obtained. Specifically, the bonding strength
is preferably in the range of about 1 to 2 N/mm2. In this connection, the
peeling/shear fracture strength of concrete is about in the range of 3 to 5 N/mm2.
By contrast, in the reinforcing member disclosed in the aforementioned
Japanese Patent Laid-Open Publication No. 8-260715, the epoxy resin to be
impregnated also serves as an adhesive. Thus, if a structural body made of
concrete is reinforced by this reinforcing member, the bonding strength will become
higher than the strength of the substrate to cause the aforementioned problems.
While any suitable adhesive satisfying the above condition may be used, the
adhesive is preferably a one-component, non-solvent adhesive. This
one-component, non-solvent adhesive may include an epoxy-urethane-based,
non-solvent, moisture-setting type adhesive. This type of adhesive
advantageously has no odor, no open time and long lifetime.
The fixation of the reinforcing member to the structure member or the substrate
can be performed without chamfering the structure member or the substrate and
adjusting the unevenness of the surface of the structure member or the substrate.
By contrast, in the reinforcing member disclosed in the aforementioned Japanese
Patent Laid-Open Publication No. 8-260715, it is practically required to chamfer the
substrate at R = 10 mm or more due to aramid fibers as a primary component of the
reinforcing member. If carbon fibers are used, R = 20 mm or more of chamfering
will be required.
In the reinforced structures according to the third and fourth modes of
embodiment, the fixation can be achieved without the large bonding strength as
described above. Thus, there is no need for any primer treatment and any
anchoring operation after the fixation. For example, only by winding the reinforcing
member around the structure member, even after peeling, the reinforcement effect
can be maintained by the geometrical constraint.
The adhesive 11 may be applied to the reinforcing member 5 at a working site
of the bonding operation. Alternatively, the adhesive 11 may be applied to the
reinforcing member 5 in advance, and stored until the bonding operation. In these
reinforced structures, in an operation of detaching or peeling the adhesive, the
substrate 3 or the reinforcing member is never damaged while leaving the adhesive
layer thereon.
When it is required to achieve the bonding constraint, as shown in FIG. 1, the
reinforcing member 5 is installed in a range (reinforcing-member installation range
9) extending outward from a range (effective bonding constraint range 7) for
reinforcing the structure member 1. The effective bonding constraint range 7 is
selectively determined depending on a required performance or function of the
structure member 1. The effective bonding constraint range 7 may be a portion of
the surface of the structure member 1. In this case, the reinforcing member 5 is
installed to form an envelope surface in the circumferential direction of the structure
member 1 or to form a surface capable of being in contact with the portion of the
surface of the structure member smoothly from the outside.
The second mechanism or geometrical constraint is achieved, for example, by
bonding both ends of a reinforcing member and installing the reinforcing member in
such a manner that it encloses a given portion (periphery etc.) of a substrate 3, as
shown in FIG. 3. In this case, the substrate 3 and the reinforcing member 5 is
geometrically connected together, and constrained to one another.
More specifically, in conjunction with the deformation of the substrate, the
length of the closed or looped reinforcing member is changed to generate a tensile
force in the reinforcing member. If the reinforcing member is installed in conformity
to the curvature or corner angle of the substrate, the tensile force will cause the
frictional force or bearing force between the reinforcing member and the substrate
so that the substrate and the reinforcing member exert a constraint force against
deformation to one another. In case where a reinforcing member is bonded in
conformity with the corner angle of a substrate, it can be expected to have a
geometrical constraint-like effect such that the bearing force of the bonded surface
at the comer is increased by the tensile force of the reinforcing member to provide
enhanced bonding strength.
While the geometrical constraint is changed depending on the shape of the
substrate 3, the relative positional relationship between the reinforcing member 5
and the substrate 3, it can be maintained until the reinforcing member 5 is fractured
even if the substrate 3 is fractured. On the other hand, the bonding constraint
disappears when the substrate 3 is fractured, and the bonding strength becomes
lower than a given value as described later.
The quantification of the effect of the reinforcing member (reinforcement effect
model) will be described below. FIG. 4 is a perspective view showing a portion of a
structure member 1 having the reinforcing member 5 installed thereon, wherein the
reinforcing member 5 elastically constrains a substrate 3 having a gap 13. The
gap is a crack or chap generated in the substrate 3. A gap width 15 (d) means the
width of the gap 13.
Upon deformation of the structure member 1, a stress is concentrated on the
reinforcing member and the surface of the structure member 1 adjacent to the gap
13 to cause the peeling of the reinforcing member 5 from the surface of the
structure member 1. In the following description, this peeled area is referred to as
"free zone 19", and the length of the free zone 19 associated with the region having
a width 23 (Δw) of the reinforcing member 5 is referred to as "free length (a)". In
the area where the bonding or geometrical constraint is achieved, the reinforcing
member 5 and the structure member are constrained to one another.
In the following description, this constrained area is referred to as "constraint
zone 21 ", and the length of the constraint zone 21 associated with the region having
the width 23 (Δw) of the reinforcing member 5 is referred to as "constraint length (a)".
When a free zone is generated, a fixation length (s) is reduced from a constraint
length (b) by a factor of a free length (a). In this case, a certain shear force, such
as a bonding or frictional force, acts between the reinforcing member 5 and the
substrate 3 in a zone (fixation zone) of the fixation length (s = b - a). While it can
be technically said that the constrained area is enlarged as the free length is
increased, this hypothesis will be ignored in the following calculation in view of a
risk-free approximate calculation.
Given that in a portion of the reinforcing member 5 of the width 23 (Δw) × the
constrained zone 21 (constrained length (b)), an average value of shear stresses 18
acting between the surface of the substrate 3 and the non-peeled reinforcing
member 5 is Tf, and a tensile force, Young's modulus and thickness in the free zone
19 of the reinforcing member 5 being q, Ef and t, respectively. The tensile force 17
and the resultant of the shear stresses 18 are balanced in the fixation zone, and
thus the following relational expression is formulated. In the following relational
expression, the reinforcing member is presupposed as an elastic body, and the
elongation in the region of the fixation length is ignored because it is small as
compared to the elongation in the free zone.
q = dEf t Δw a = (b -a )τ f Δw
The following relational expression can be obtained by eliminating "a" from the
expression [1], dividing by tΔw, and giving that a tensile stress of the reinforcing
member 5 is σf.
σ f 2 - b t τ f σ f + d t Ef τ f = 0
From the condition of the real root of σf, it can be proved that a gap width d is
between 0 (zero) and
d max = b 2 τf 4Ef t .
For a certain gap width d, two of σf will be derived as a solution. Given that
larger one of them is achieved, a maximum value σfmax and a minimum value σfmin of
σf are expressed as follows:
σf max = b t τf , σf min = 0.5σ f max
σfmax is a stress in the condition of the gap width d = 0 or at the time when
the gap 13 is just generated on the surface of the structure member 1. σfmin is a
stress at the time when the gap 13 is enlarged, and the gap width d reaches a value
dmax in the expression [3]. According to the expressions [1] to [3], when the tensile
stress of the reinforcing member 5 is σfmin, the free length (a) is calculated as 1/2 of
the constraint length (b). If the gap width d is increased at a value larger than dmax,
the expression [1] will be invalid in view of dynamical theories, the free length (a)
will be sharply increased until a certain constraint such as geometrical constraint is
given again.
The change in the length (hereinafter referred to as "circumferential length") L
of the envelope (the circumference of the envelope surface) can be presupposed as
the change in the total value d of the gap width across the circumference. Thus,
the following formula is satisfied between a circumferential strain and the total
value of the gap width measured along the circumference. In the following formula,
L0 is the circumferential length before the generation of the gap.
d = L0
Further, given that the reinforcing member 5 is elongated only in the free zone
(free length a) where the fixation between the reinforcing member 5 and the
structure member 1 is separated, the following relational expression of the
circumferential strain and the strain εf of the reinforcing member by focusing on
the elongation of the reinforcing member 5 installed to form the envelope surface:
a L 0 = Φε f
, wherein a/L0 is an index indicating the level of the constraint, and thus hereinafter
referred to as "constraint rate".
The tensile force 17 (σf) of the reinforcing member 5 can be calculated as
follows in accordance with the strain (εf) and Young's modulus (Ef) of the reinforcing
member 5. In the following formula, a secant Young's modulus will be used if the
Young's modulus of the reinforcing member is changed dependent on the strain
thereof.
σ f = εf Ef
Given that after the structure member 1 is fractured by the action of repeated
load, it can be approximated as a granular body, the following relational expression
is satisfied:
σ f = B 2t σ3
, wherein B is the distance (sectional width) between the reinforcing members, and
σ3 is a constraint pressure of the granular body.
The following relational expression can be obtained by applying the
relationship between the primary stress σ1 and constraint pressure σ3 of the
granular body to the expression [8]:
σf = B (1 - sin ϕ) 2t (1 + sin ϕ) σ1
In the state of axial compression, the value of the primary stress s1 can be
approximated as a value derived from dividing a compressive force by a
pressure-receiving sectional-area. On the other hand, under the condition of
receiving a shear force, it is required to calculate with the inclusion of the influence
of the shear force.
The relationship of the tensile force of the reinforcing member, the deformation
causing a gap of the structure member and the fixation force is obtained from the
expressions [3] to [7] and [9]. Further, since the deformation causing a gap would
represent the level of the damage of the substrate, the relationship between the
damage of the substrate and the tensile force (or strain) of the reinforcing member
can also be obtained.
The above model is unconfined by the type of the gap 13. Specifically, the
model is applicable to any gap 13 caused by any factor including a dynamical factor,
such as bending or shear, and a material factor, such as temperature, dryness,
expansion or deterioration. According to the model, particularly when the
reinforcing member 5 is installed in a direction crossing to a gap 13 caused by shear
(shear chap, shear fracture surface, etc.), it can elastically constrain the
surrounding of the gap 13 to control a shear deformation at a finite value and
maintain the toughness of the structure member 1.
Further, the above model is unconfined by the type of the substrate 3. The
substrate 3 may be any construction material, such as reinforced concrete, steel
framed reinforced concrete, steel frame, brick, block, gypsum or plaster board,
precast concrete product, wood, rock, sand or resin. The substrate 3 may be an
existing structural or non-structural martial or a newly installed material.
The installation of the reinforcing member 5 may be a portion of the structure
member as long as it is wider than an area (effective bonding constraint range 7)
corresponding to the constraint zone 21 (constraint length (b)) for the crack or gap
13. Referring to FIG. 1, the area of the effective bonding constraint range 7 in the
reinforcing-material installation range 9 is an effective range.
According to the expressions [3] and [4], the reinforcement effect is
superficially increased in proportion to the bonding strength. However, if the
bonding strength is set at a value close to the full strength of the substrate 3 or the
reinforcing member 5, the substrate 3 or the reinforcing member 5 will be locally
fractured before generation of a free length (a) to annul the reinforcement effect.
Thus, the bonding strength is required to be set at a level causing no fracture in the
substrate 3 and the reinforcing member 5 in the above process.
The aforementioned model can be achieved if the reinforcing member 5 is not
fractured by a stress concentration arising around a crack or gap or at a corner of
the structure member 1 in connection with the generation and enlargement of the
gap 1 in the structure member 1. Thus, it is also required to provide extensibility
(large fracture strain) to the reinforcing member 5. While carbon fibers or aramid
fibers have a large elastic coefficient and fracture strength, any material having a
small fracture strain is not suitable as the reinforcing member in the first mode of
embodiment and another after-mentioned mode of embodiment.
The model can also be achieved if the reinforcing member brings out a
sufficient performance even after the adhesive layer between the substrate and the
reinforcing member is partly fractured. Thus, a continuous-fiber reinforcing
member whose performance is defined under the condition of a structure in which a
carbon or another fibers bound by resin are bonded on the surface of a substrate
without float and wrinkle is not suitable as the reinforcing member in the first mode
of embodiment and another after-mentioned mode of embodiment.
Further, the reinforcing member 5 is also required to have elasticity to bring out
a control effect to the phenomenon that the gap 13 is opened and closed by a
repeated alternate load.
The quantification of the performance of a structure member 1
(structure-member performance model) will be described below. The dynamic
performance and durability of the structure member can be quantified in
consideration of the performance of a substrate and a desired reinforcement effect.
The following description will be made in conjunction with one example in which a
substrate 3 of the structure member 1 is a bar-shaped member made of reinforced
concrete, and the substrate 3 is reinforced by the reinforcing member 5 and
subjected to repeated shear.
As mentioned in connection with the reinforcement effect model, even after a
shear gap is generated in a structure member 1 due to a repeated shear force
applied thereto, a shear force will be transmitted through the reinforcing member 5
across the gap to cause a bending deformation and maintain the toughness of the
structure member 1. The reaction force of the reinforcing member 5 is borne by
the bonding constraint until the tensile force of the reinforcing member 5 is
increased up to σfmin in the expression [4], and subsequently borne by the
geometrically constraint.
Then, when the substrate 3 is increasingly fractured by the work of repeated
load action to have dynamic characteristics such that they can be approximated as
those of a granular body (dense sands) having a surface covered by an elastic body,
a shear yield strength is increased as the deformation of the structure member is
increased. Therefore, a shear load-deformation relationship has two extreme
values, as described later in conjunction with FIGS. 5, 12, etc.
FIG. 5 is a graph schematically showing the above relationship between load
and deformation. The horizontal axis represents a deformation (deformation
angle) in a structure member 1, and the horizontal axis represents a load acting on
the structure member 1. The shape of the curve is described by ten parameters or
Qmax1, α Qmax, Qmid, Qmin, Qmax2 and R1 to R5. Qmax1 is an initial maximum vale of
the load, α Qmax being the load in a limit state (design ultimate state etc.), Qmin being
a minimum value of the load, Qmid being the load by which the bonding constraint is
released and shifted to the geometrical constraint, and Qmax2 being the load by
which the reinforcing member 5 is fractured, or the deformation of the structure
member 1 reaches at an extreme value and becomes unable to bear any load. R1
to R5 are the deformations corresponding to Qmax1, α Qmax, Qmid, Qmin, Qmax2,
respectively. The limiting point 27 (Qmin, R4) is a point where the structure member
1 is fractured by load, and starts exhibiting behaviors of a granular body.
FIG. 6 is a graph showing the relationship between circumferential strain and
deformation in the structure member. The horizontal axis represents a
deformation (deformation angle) in the structure member 1, and the horizontal axis
represents a circumferential strain in the structure member 1. The change in an
apparent volume, or a volume associated with an envelope surface, of the structure
member 1 is expressed by a circumferential strain (strain in the circumferential
length of the section of the structure member 1 in a direction perpendicular to the
axis thereof) and an axial strain (strain in the axis of the structure member 1). The
circumferential strain is changed as shown in the graph 29 in response to the
change of the relationship between the load and the deformation in FIG. 5.
(R1, 1), (R2, 2), (R3, 3), (R4, 4) and (R5, 5) in FIG. 6 correspond to (R1,
Qmax1), (R2, α Qmax), (R3, Qmid), (R4, Qmin) and (R5, Qmax2), respectively.
The circumferential strain is gradually increased as the bonding is separated to
increase a free zone 19. In the range of R3 to R4, the circumferential strain is kept
approximately constant by the geometrical constraint. When the deformation goes
beyond R4, the circumferential strain will be increased again because the structure
member 1 behaves as a granular body. The axial strain is changed in the same
manner as that of the circumferential strain.
The result of an experimental verification will be described below. While the
structure member is described as a column in the following description, it is not
limited to such a column.
FIG. 7 shows the state when a region having the width 39 (H) of a structure
member 31 reinforced by a reinforcing member 37 is divided into a first segmental
member 33 a second segmental member 35 by a structural gap 41 (gap width 43
(d)), and the opposite ends of the divided structure member receive the action of a
shear force 45 (Q). The reinforcing member 37 is installed to form an envelope
surface in the circumferential direction of the structure member 31 or to form a
surface capable of being in contact with the portion of the surface of the structure
member smoothly from the outside. The shear force 45 is being transmitted
between the first and second segmental members 33, 35 through the reinforcing
member 37 in each section.
FIG. 8 is a perspective view of the section (thickness 47 (ΔH)) perpendicular to
the axis of the structure member in FIG 7. Each of shear forces,
reinforcing-member tensile stresses 51 (σf), and tensile forces 53 (σcs) of concrete
and reinforcing bar acts on the structure member 31 (first and second segmental
members 33, 35) and the reinforcing member 37. Among the shear forces, a first
shear force to be transmitted from the upper surface of the first segmental member
33 to the lower surface of the second segmental member 35 through the reinforcing
member 37 is defined as a transmission shear force 49 (ΔQf). While not shown,
there is a second shear force to be transmitted in the opposite direction of the first
shear force or from the upper surface of the second segmental member 35 to the
lower surface of the first segmental member 33 at the same value as that of the first
shear force.
Given that the tensile force 53 (σcs) is 0 (zero) for the purpose of simplifying the
description without losing universality, the difference between the shear forces in
the upper and lower surfaces of the first segmental member 33 provides the
transmission shear force 49 (ΔQf). The same goes for the second segmental
member 35.
Given that the thickness 47 (ΔH) is infinitely small, and a body force and a
moment with an arm having a length in the thickness direction are ignored. Further,
given that there is no distributed load, and the reinforcing member 37 bears only the
tensile stress 51 for the purpose of simplicity. Furthermore, given that the
transmission shear force 49 (ΔQf) acts to the reinforcing member 37 such that the
front-side and back-side tensile stresses 51 (σf) become equal to each other, and
ΔQ/ΔH is constant, the following relation is satisfied in view of a balance expression:
σ f = Qf 2Ht
, wherein t is the thickness of the reinforcing member 37, and Qf is a value derived
by eliminating the shear forces transmitted through concrete and reinforcing bar
from the shear force 45(Q). Given that the Young's modulus of the reinforcing
member 37 is Ef, a reinforcing-member strain εf can be expressed by the following
expression.
εf = σ f Ef = Of 2Ef Ht
The result of an experimental test on the effect of the above reinforcing
member, and the performance of a structure member having the reinforcing
member installed thereon will be described below. The test was carried out using
an RC column (SRF-reinforced model column) having the above reinforcing
member installed thereon and a non-reinforced RC column (non-reinforced model
column) (SRF: Soft Retrofitting for Failure). The outline of the test is shown as
follows.
- An axial force and a repeated shear force are applied to the column while constraining the rotation of the capital and base of the column.
- A horizontal force is applied to the capital through a rigid frame having a loading point at the center of the column.
- Under a displacement control, deformation angles of 1/400 to 4/400 are applied in the positive and negative displacements two times, and then deformation angles of 6/400, 8/400, 16/400, 24/400, 32/400, 48/400 and 64/400 are applied in the positive and negative displacements one time, and finally, a deformation angle of 200/900 as a limit of a pressure device is applied.
Fourteen cases were tested under a variable axial force and a constant axial
force. Among these cases, the results of nine cases under a constant axial force
were used to quantitatively evaluate the performance of the above SRF reinforcing
member.
FIG 43 is a chart showing properties (test specifications) of the tested columns,
loading conditions, test results, and SRF reinforcement effects, on the nine cases
under a constant axial force.
FIG. 10 is a graph showing the relationship between horizontal load and
deformation (restoring force characteristic) on the non-reinforced model column
(Case 8). The horizontal axis represents a deformation (δ (mm)), and the vertical
axis represents a horizontal load (Q (kN)). In a deformation angle of 0.6% (1/166),
a maximum load was increased up to 237 kH (Qmax), and the non-reinforced model
column could not bear the axial force (η = 0.3) in a cycle having a deformation angle
of greater than 1.5%.
FIG 11 a graph showing the relationship between horizontal load and
deformation (restoring force characteristic) on the SRF-reinforced model column
(Case 9). The horizontal axis represents a deformation (δ (mm)), and the vertical
axis represents a horizontal load (Q (kN)). The model column was reinforced by
bonding a reinforcing member formed of a polyester woven fabric having a
thickness (t) of 4 mm, around the model column. The properties of the reinforcing
member are shown in FIG 43. The bonding strength is about 1 MPa.
In a deformation angle of 0.9%, a maximum load was increased up to 258 kH
(Qmax), and the horizontal load is maintained at a value of 80% (0.8 Qmax) or more of
a maximum horizontal load until the deformation angle goes beyond 4.0%. Given
that 0.8 Qmax is a design ultimate state, an ultimate toughness coefficient (µ) is 6.
In the subsequent loading cycles, the peak load is gradually reduced, and
minimized (61: minimum point of the peak load) at a deformation angle of 64/400.
In the next cycle, the peak load is increased.
FIG. 12 is a graph showing the relationship between the peak value of the
horizontal load and the deformation in each of the loading cycles, on the nine cases
under a constant axial force in FIG 43. The horizontal axis represents a
deformation angle (R (%)), and the vertical axis represents a maximum horizontal
load (peak load) in a positive direction in each of the loading cycles. Numerals in
the figure indicate the case numbers illustrated in FIG. 43.
Referring to FIG 11, in all of the reinforced cases (Cases 2, 3, 5, 9 and 13), a
maximum point (maximum value Qmax), a minimum point (minimum value Qmin) and
an apparent gradient-change point (Qmid: peak load at the change point) are
observed. For example, in Case 9, a maximum point 63, a minimum point 65 and
a gradient-change point 67 are observed. The Case 2 with a small reinforcement
amount has a smaller R4 (deformation angle at the minimum point) than that of other
cases.
For each of these cases, Qmid/Qmax and Qmin/Qmax were calculated based on
the above maximum point, minimum point and gradient-change point. The result
is shown in FIG 62. Qmid/Qmax becomes approximately equal to a theoretical value
of 0.5 according to the expression [4]. Qmin is reduced from Qmid only by about
10% thereof. This result supports the validity of the aforementioned quantification
of the effect of the reinforcing member.
FIG. 13 is a graph showing the relation between structure-member
circumferential-length elongation strain and deformation. The horizontal axis
represents a deformation angle (R (%)), and the vertical axis of a structure-member
circumferential-length elongation strain ((%)). The measurement was performed
along five lines provided around the reinforced columns at even intervals. As a
result, all of the lines were uniformly elongated, which supported the validity of the
expression [10]. The average values of the test results was plotted to prepare FIG.
13.
Referring to FIGS. 12 and 13, it is proved that the change of a peak load and
the change of a circumferential strain in each of the cycles have an extremely
strong correlation as with FIGS. 5 and 6 which have been schematically shown.
That is, most of a shear force after the maximum load Qmax is borne by the
reinforcing member according to the mechanism which has been described in
conjunction with FIGS. 7 and 8.
In this way, the design calculation can be performed according to the
aforementioned quantification models of the reinforcement effect and the
performance of a structure member having a reinforcing member installed thereon.
For the purpose of comparison, the index (reinforcement efficiency) K
representing the reinforcement effect, which is defined by the following expression
[12] according to a method of Japan Society of Civil Engineers, was calculated
under the condition of a design ultimate state of 0.8 Qmax:
S = Sc + Ss + K Ss (A f , ffud )
, wherein S is a shear strength after reinforcement, Sc being a shear strength
calculated from a concrete strength etc., Ss being a shear strength calculated from
a shear reinforcing bar etc., and Ss (Af, ffud) being a reinforcing-member section Af
and a reinforcing-member strength f fud which are substituted with corresponding
values in a SRF reinforcing member. FIG. 62 shows the calculated K
(reinforcement efficiency).
Further, a design strength σ fd of the reinforcing member was calculated back
according to a method defined in the design/installation manual for continuous-fiber
reinforcement of Architectural Institute of Japan. FIG 43 shows the ratio
(reinforcement efficiency: σ fd/σ fmax) of the design strength σ fd to a fracture strength
σ fmax of a SRF reinforcing member. In the above calculation, a shear strength S
after reinforcement was calculated by determining a shear margin from a roughness
coefficient. The calculation was also performed on the assumption that a yield
deformation angle was 1/250 in all of the cases.
The reinforcement efficiencies in the both methods (K, σ fd/σ fmax) are an
approximately the same value of about 0.2 in the case of Fc = 3.5 MPa. In the
case of Fc = 18 MPa, it is observed that the value tends to be increased. In
particular, this tendency is significant in the latter method (σ fd/σ fmax). This would
result from evaluating the reinforcement effect as the square root of a reinforcement
amount. On the reinforcement efficiency K, there have been reported
experimental values in the range of 0.8 to 1.0 for carbon fibers, and about 0.4 for
aramid fibers.
In the above test, a small value or about 0.2 less than that in the
aforementioned conventional techniques and 1.0 in a reinforcing bar is obtained.
This results from the difference in the material or a low Young's modulus of the
reinforcing member, and the methodological or structural difference or a mechanism
based on the peeling and displacement caused between the reinforcing member
and a substrate.
The result obtained by calculating the circumferential strain in the design
ultimate state (0.8 Qmax) from an actually measured circumferential length is shown
in FIG 62. An actually measured ultimate circumferential strain (2) is in the range
of 0.2 to 0.4%, and thus the damage level of the inside of the structure member is
equivalent to that in the conventional techniques such as the reinforcement using
carbon fibers.
A reinforcing-member strain (εf) was calculated from an actually measured
shear load (Q) (see the expression [11]), and then a constraint rate (a/L0) was
calculated from the calculated reinforcing-member strain (εf) and an actually
measured circumferential strain () (see the expression [6]). This constraint rate
(a/L0) is shown in FIG 62. The constraint rate (a/L0) is the ratio of a free length (a)
to a circumferential length (L0).
In this test, the tested reinforced column receives a shear force from one
direction. For example, given that when a gap is generated in a surface parallel to
a direction of the shear force and thereby a bonding constraint is completely
released and shifted to a geometrical constraint, two surfaces of the
circumference of a square section provide resistance, the constraint rate (a/L0) is
theoretically 0.5.
Referring to FIG. 43, the tested reinforced column has a constraint rate (a/L0) <
0.5 in Cases 3 and 5, and a constraint rate (a/L0) > 0.5 in Cases 9 and 13. Thus, it
can be said that in the design ultimate state, while a bonding constraint in Cases 3
and 5 having a deformation angle R2 of 1 to 2% is still effective, a bonding
constraint in Cases 9 and 13 having a deformation angle R2 of 4 to 6% is released
and completely shifted to a geometrical constraint.
As in the above observation on the test results, the validity of the model for the
effect of a reinforcing member (reinforcement effect model) and the model for the
performance of a structure member with a reinforcing member installed thereon
(structure-member performance model) has been verified. It is understood that
the aforementioned numerical values are experimental values, and a safety factor
coping with variations must be used in actual designs.
A method for determining the material, thickness, installation range and others
(or for designing) of the reinforcing member of the present invention will be
described below.
FIGS. 39 and 40 are design flowcharts for a reinforcement amount in a process
of reinforcing a structure member through a method of the present invention. With
reference to the flowcharts in FIGS. 39 and 40, a method of determining
reinforcement parameters will be described below.
As shown in FIG 39, limit conditions of the weight, shape, function and others
of a structural body are first determined (Step 301). Concurrently, the amplitude,
cycle or period, duration and energy of a sudden external force likely to act on the
structural body are determined (Step 302). Among the sudden external force likely
to act on the structural body, a burden share to be bome by a substrate of the
structural body, such as reinforcing bar and concrete, is also determined (Step 303).
Then, in a design process (a) of determining parameters of a structure member
when a structural body or a structure member is newly constructed, the parameters
of the structure member are determined in consideration of the data determined in
Steps 301 to 303 (Step 304). The parameters of the structure member may be
determined using conventional structural design/calculation methods or any other
suitable reinforcement manuals.
Then, Among each of a load in ordinary condition, such as the weight of the
structure member itself, and the sudden external force, a burden share to be bome
by a method of the present invention is determined (Step 305). Specifically, this
step is intended to determine the type, property, and magnitude (amplitude, period,
duration, and energy) of the sudden external force to be bome by the method,
structure or material of the present invention. These data may be obtained by
subtracting the energy of a sudden external force bearable with other factors than
the reinforcement according to the method of the present invention (the burden
share of the substrate etc. determined in Step 303) from the total energy of the
sudden external force likely to act on the structural body in the durable term thereof,
which has been determined in Step 301. Thus, if the reinforcement of the present
invention is used in a structural design for a new construction, the materials and/or
parameters of a structure member can be determined in an economically
advantageous manner by a factor of the reinforcement of the present invention.
In a design process (b) involving no determination of any parameter of a
structure member, for example, in a design process of reinforcing an existing
structural body or structure member using the reinforcing member, the data in Step
305 are determined from the data determined in Steps 302 and 303. In this
process, such data may be obtained by subtracting a sudden external force
bearable with other factors than the reinforcement according to the method of the
present invention from the total energy of the sudden external force likely to act on
the structural body in the durable term thereof, as with the process (a).
Then, the amplitude and energy of a sectional force to act on the structure
member are calculated (Step 306). Specifically, based of the type, property and
magnitude of the sudden external force determined in Step 302, the amplitude and
magnitude of a sectional force (shear force, axial force, bending moment, etc.) to
act on a structure member including a reinforced structure member and other
structure members, and a deformation (shear strain, axial strain, bending strain,
etc.) of the structure member. Concurrently, the displacement amplitude and
vibrational energy of the entire structure body to be induced by the sudden external
force are calculated (Step 307).
The data in Step 306 or 307 may be rigorously calculated by performing a
structural analysis calculation, such as a finite element method or frame analysis
method taking account of a restoring force characteristic of a reinforced structure
member and other structure members as shown in FIG 51. Alternatively, the data
in Step 306 or 307 may be calculated by simplifying a structural system and setting
assumptions such as energy formulas, as in practical structural designs. Except
that an associated deformation range is wider than that in a conventional calculation,
the calculations in Steps 306 or 307 can be performed in the same manner as that
in a structural design for a structure member having a known restoring force
characteristic.
Then, the relationship of a reinforcement amount, a restoring force
characteristic and an axial strain of the reinforced structure member is determined
(Step 308). The data in Step 308 are determined by the calculations in Steps 306
and 307. In Step 308, it is generally required to perform a feedback from 310 to
Steps 306 and 307 through Steps 308, as indicated by the dashed lines of FIG 59.
Then, limit conditions of the function, usability, recoverability and others of the
structural body after the action of the sudden external force such as a seismic force
are determined (Step 309), and the determined limit conditions are compared with
the displacement amplitude and vibration energy of the structural body calculated in
Step 307 to determine reinforcement parameters (Step 310).
Specifically, the reinforcement parameters are determined by comparing the
deformation of the structural body calculated in Steps 306 to 308 with an allowable
deformation amount to be derived from the conditions determined in Step 309 or the
use conditions of the structural body after the action of the sudden external force
such as a seismic force. Step 310 is performed in consideration of the limit
conditions of the weight, shape, function and others of the structural body which
have been determined in Step 301.
If the conditions in Step 309 are determined based on the policy of simply
preventing collapse against a large earthquake, the allowable deformation can be
set at a large value. If a large deformation involves the risk of disaster such as
derailment even immediately after occurrence of a large earthquake, as in an
elevated railroad for the bullet train, the reinforcement amount will be determined in
consideration of such a factor.
Further, if a design ultimate state is defined by a load-withstanding capacity
(strength) corresponding to a given deformation angle of a structure member, the
reinforcing member can be designed by the following process.
In the above Steps <1> to <3>, the expressions [5] to [11] or modified
expressions obtained by modifying the expressions [5] to [11] according to the
conditions of the structure member. In this case, the reinforcement design has to
be performed using a sufficient safety factor for a fracture strain because there is a
possibility of causing a strain several times larger than the reinforcing-member
strain ε f in the expression [11]. Further, in the calculation of Qf, a shear force
transmitted by a substrate (a shear force transmitted by concrete. reinforcing bar or
the like, etc.) may be subtracted, or the subtraction of this shear force may be set at
0 (zero) on the safe side.
A load-withstanding capacity of the structure member after the structure
member goes beyond the above design ultimate state can also be calculated using
the expressions [8] and [9]. However, in an actual design, the performance of the
structure member and the reinforcement amount are experimentally checked as
needed as in a conventional design for reinforced concrete members.
The expressions [5] to [11] are valid even if the substrate is not a structural
material such as concrete. Therefore, a structure member can be produced using
a substrate consisting of a material, such as brick or block, which has been
considered as a non-structural material,
However, if the rigidity of a substrate is less than that of the reinforcing member,
the deformation of the substrate will be increased before development of a
reinforcement effect, and a design process including a calculation required for
taking account of the increase deformation will be complicated as compared to the
above process. Thus, the material of the reinforcing member is selected such that
the Young's modulus of the reinforcing member is less than that of the substrate, as
described above. However, if the Young's modulus of the reinforcing member is
excessive low, the thickness of the reinforcing member required for obtaining a
desired reinforcement effect will be increased as shown in the expressions [3] and
[11]. Specifically, the material of the reinforcing member is selected from one
having a Young's modulus preferably in the range of about 1/2 to 1/20, more
preferably about 1/5 to 1/10, of that of the substrate.
The bonding constraint mechanism becomes effective for a larger gap and can
suppress the deformation (circumferential strain) of the substrate at a smaller value
as the reinforcing member has a larger Young's modulus in the design ultimate state.
This deformation (circumferential strain) of the substrate is quantified by the
expressions [3] and [11].
FIG 9 is a graph showing a stress-strain relationship of the reinforcing member.
The horizontal axis represents a strain (ε) of the reinforcing member, and the
vertical axis represents a stress (σf) of the reinforcing member. As described
above, the reinforcing member is required to have extensibility (large fracture strain).
In this regard, the design for the reinforcing member and others is preferably
performed in consideration of the curve of the stress-strain relationship as shown in
FIG. 9.
Preferably, on the curve of the stress-strain relationship in FIG 9, the ratio 59
(σ fu/ε fu) of a stress σ fu of the reinforcing member to ε fu of the reinforcing member
in a design ultimate state 57 of a structure member is defined as a Young's modulus
Ef of the reinforcing member in the design ultimate state, and the design of the
reinforcing member and others is performed using the Young's modulus Ef, and a
fracture strain ε max and fracture stress (strength) σ max of the reinforcing member
The reinforcing member is selected to satisfy a desired performance of the
reinforced structural with reference to the expressions [1] to [9]. When a polyester
woven fabric or the like is used as the reinforcing member, it may be heated to
provide a tensile force thereto, and then cooled while maintaining the tensile force
or subjected to a treatment for impregnating the reinforcing member with resin
(resin impregnation treatment), to provide Ef larger than σ fu/ε fu. The reinforcing
member subjected to the above treatment can have a higher reinforcement efficient
(reinforcement effect per unit thickness) than that of the reinforcing member without
the treatment, to achieve a reduced material cost.
A reinforced structure will be described below in conjunction with an example
where a structure member is a walled column. FIG 14 is a perspective view of a
walled column with the reinforcing member installed thereon. The walled column
comprises a column 71 and a wall 73. The reinforcing member 75 is installed in
such a manner it is wound around the column 71 and bonded on a
reinforcing-member installation range 79. The reinforcing-member installation
range 79 has a larger area than that of an effective bonding constraint range 77.
The effective bonding constraint range 77 corresponds to a given constraint length
(b). The wall 73 is formed with no through-hole for installing the reinforcing
member 75.
An epoxy-urethane-based one-component adhesive (bonding strength Tf = 1
MPa) is used for the bonding. A polyester sheet member (Young's modulus Ef =
2100 MPa, thickness t = 2 mm) is used as the reinforcing member 75.
Given that a shear force applied in X direction causes a gap in a surface
parallel to X direction, a restraint length (b) allowing the bonding constraint to be
effectively maintained until the total (d) of the gap width measured along a
circumferential length parallel to X axis is increased up to 2 mm is calculated as b =
1183 mm according to the expression [3]. Given the a safety factor is 2, a design
constraint length (bd) is about 40 cm.
FIG 15 is a sectional view of the walled column 69 in FIG 14. The design
constraint length (bd) corresponds to the effective bonding constraint range 77 in
FIGS. 14 and 15.
While a shear bearing force of the walled column 69 is obtained by assigning
the dimensions of the column 71, the strength of the reinforcing member 75, the
strength of the adhesive and others to the expressions [4] and [10], it is desired to
experimentally check it as needed because the reinforcement effect and the
geometrical restraint limit are different from those in case where the reinforcing
member is fully wound around the column.
A restoring force characteristic in the state after the shear force goes beyond
the design ultimate state to cause fracture of the walled column 69 and thereby the
bonding restraint is completely released and shifted to the geometrical restraint can
be calculated according to the expressions [8] an [9].
In this state, at the joint portion between the column 71 and the wall 73, the
stress σf of the reinforcing member 75 is transmitted through the inside of the
substrate. Thus, the limit ((Qmax2, R5): FIG. 5) of the validity of the geometrical
restraint is determined by smaller one of the strength of the reinforcing member and
the strength of the substrate at the joint portion. At any rate, the geometrical
restraint can be maintained up until the limit (Qmax2, R5) without forming a hole or the
like in the walled column 69 and penetrating the reinforcing member therethrough.
FIG 16 is a sectional view of the walled column 69 in FIG 14. While the
reinforcing member 75 installed around the column 71 is opened at the joint plane
between the column 71 and the wall 73, a portion of the column 71 in this open
zone 183 is constrained by the wall 73 having the reinforcing member 75 installed
thereon. Thus, the entire circumferential of the column 71 is constrained by the
reinforcing member 75 and the wall 73 having the reinforcing member 75 installed
thereon. In this case, the geometrical constraint is achieved in an effective
geometrical constraint range 81.
Alternatively, a given reinforcement effect can be obtained by installing the
reinforcing member on only one of the surfaces of a structure member such as wall.
Further, a earthquake-resisting wall may be formed by placing a pair of boards,
such as precast concrete boards, in parallel with one another between two existing
columns to form a wall, pouring concrete or filling sands or the like into the space
between the boards, and installing the reinforcing member around the wall and/or
the columns.
Thus, according to the above reinforced structure, the reinforcing member
having a given rigidity and extensibility is installed a portion of the surface of a
structure member to be reinforced, to reinforce the structure member. Thus, the
reinforcement can be applied to a structure member having any shape such as a
convexo-concave or irregular shape. In addition, the reinforcing member can be
installed without forming any hole or the like in a structure member subject to
reinforcement. Therefore, a reinforced structure excellent in toughness and
load-withstanding capacity can be constructed quickly and readily at a low cost.
Further, the reinforcement effect of the reinforcing member and the
performance of the reinforced structure with the reinforcing member can be
quantified and/or evaluated according to the aforementioned reinforcement effect
model and structure-member performance model. Thus, the reinforcing member
can be adequately selected and designed depending on a structure member
subject to reinforcement.
As seen in the reinforcement effect model and the structure-member
performance model, the reinforcing member and the adhesive according to the first
mode of embodiment can be effectively selected depending the material, category
and type (existing or new construction, etc.) of a structure member. Thus, the
labor load and cost for constructing the reinforced structure having a desired
performance and preparing/installing the reinforcing member having a desired
reinforcing effect or quake-resistance effect can be constructed can be reduced
while shortening a construction period.
As a substitute for the reinforcing member 75, a strip-shaped polyester belt
199 as shown in FIG 21 may be used. The material of the polyester belt 199 may
be polyester-based fibers for use in bell rope or the like. While a reinforcing sheet
such as a construction sheet has a strength in the range of 500 to 1000 kgf/3 cm
width, the polyester belt 199 has a strength of about 15000 kgf/5 cm width.
Another reinforced structure will be described below in conjunction with an
example where a structure member has an H shape. FIG 17 is a perspective view
of an H-shaped structure member 143 after reinforcement. As shown in FIG 17,
the H-shaped structure member 143 is reinforced using a reinforcing member 145
and a granular filler material 147.
The sheet-shaped reinforcing member 145 is shaped into a cylindrical shape
and disposed around the H-shaped structure member 143 to form a space
therebetween. The granular filler material 147 is filled in the space between the
H-shaped structure member 143 and the reinforcing member 145. For example, a
fiber or rubber-based sheet material may be used for the reinforcing member 145.
For example, the filler material 147 may be a natural granular material, such as
sands, or an artificial granular material, such as resin.
The glandular filler material 147 transmits a stress to the reinforcing member
145 while being deformed in connection with energy loss. Thus, differently from
the conventional reinforcing techniques such as continuous fibers or steel-plate
wrapping, there is no need for fixing the filler material with resin or adhesive. Even
if the filler material is bonded or fixed for the reason of construction, the bonding or
fixation may be performed in a temporary level allowing the shape of the filler
material to be held under ordinary loading or in earth tremor.
This type of reinforced structure may be used to reinforce a structure member
having a complicated sectional shape, as well as the H-shaped structure member
143. In this type of reinforced structure, when the structure member is deformed in
connection with an apparent volume expansion, the granular filler material 147
transmits the apparent volume expansion to the reinforcing member to provide
enhanced reinforcement effect. Further, the granular filler material may be formed
of an inorganic noncombustible material having high heat capacity to have an
additional effect of protecting the H-shaped structure member 143 from heat.
Still another reinforced structure will be described below in conjunction with an
example where a structure member is hollow. FIG 18 is a perspective view of a
hollow structure member 149 after reinforcement. As shown in FIG. 18, the hollow
structure member 149 is reinforced using a reinforcing member 145 and a granular
filler material 147.
The sheet-shaped reinforcing member 145 is installed on and around the outer
surface of the cylindrical hollow structure member 148. The inside of the hollow
structure member 149 is filled with the granular filler material 145. For example, a
fiber or rubber-based sheet material may be used for the reinforcing member 145.
For example, the filler material 147 may be a natural granular material, such as
sands, or an artificial granular material, such as resin.
The granular filling material 147 is installed to fill the space of the hollow
structure member 149. In addition, the glandular filler material 147 transmits a
stress to the reinforcing member 145 while being deformed in connection with
energy loss. Thus, there is no need for solidifying the filler material filled in the
inside of the structure member as in concrete used in a concrete-filling steel-pipe
construction method.
In this reinforced structure, when a hollow structure member is reinforced, the
granular filler material 147 is installed inside the structure member to provide
enhanced reinforcement effect. The filler material acts to transmit to the
reinforcing member 145 an apparent volume expansion cased when the hollow
structure member 149 is fractured in connection with energy loss. While the
hollow structure member in the above example has a circular sectional shape, the
present invention is not limited to such a shape.
In addition, in order to reinforce the H-shaped structure member 143 or the
hollow structure member 149 used the glandular filler material 147, compounding
this reinforced structure and other reinforced structure can be applied.
Next, an example of the reinforced structure in case of using plurality of
reinforcements will be described. FIG. 19 is a partial sectional view of a reinforced
member 181. In FIG 19, the member 181 is reinforced by use of a protective
reinforcement 183, a reinforcement 185, a reinforcement 187, and a protective
reinforcement 189.
The protective reinforcement 183, the reinforcement 185, the reinforcement
187, and the protective reinforcement 189 are sequentially, from inside to outside,
disposed on the member 181. The protective reinforcement 183 is disposed in
order to protect the reinforcements 185 and 187 and the protective reinforcement
189 from the action of the member 181. For example, when the member 181 is
made of a material, such as concrete, from which alkali separate outs, and the
reinforcements 185 and 187 and the protective reinforcement 189 are made of a
material, such as polyester fiber, of low alkali resistance, the protective
reinforcement 183 is made of a material, such as a resin, which has a function to
prevent separation of alkali from the member 181.
The protective reinforcement 189 is disposed in order to prevent a
deterioration in the function of the protective reinforcement 183 and the
reinforcements 185 and 187 which would otherwise result from the action of
substances in the external environment. For example, when the protective
reinforcement 183 and the reinforcements 185 and 187 are polyester-fiber sheets or
the like, these reinforcements are likely to be deteriorated by ultraviolet rays. Thus,
the protective reinforcement 189 is made of epoxy, urethane, or a like resin to
thereby prevent a deterioration of the reinforcements disposed inside the same. A
fireproof belt can also be used as the protective reinforcement 189.
The reinforcement 185 and the reinforcement 187 differ in a reinforcement
effect on the member 181. For example, the reinforcement 187 is made of
polyester fiber or the like, and the reinforcement 185 is made of a resin or fiber
impregnated with resin. In this case, the reinforcement 187 exhibits a
reinforcement effect at up to a large strain (up to about 15%) of the member 181,
whereas the reinforcement 185 exhibits a reinforcement effect at a low strain (not
greater than 1 %) of the member 181.
When the member 181 is to be reinforced merely by use of a polyester fiber
reinforcement, the reinforcement must assume a large thickness in order to exhibit
a reinforcement effect at the stage of a small strain of the member 181, since the
reinforcement is smaller in Young's modulus than the member 181. However,
through combined use of the polyester fiber reinforcement and a reinforcement
made of a material, such as a resin or fiber impregnated with resin, having a large
Young's modulus, the polyester fiber reinforcement thinner than that used solely for
reinforcing the member 181 can exhibit a reinforcement effect even at a small strain
(not greater than 1%) of the member 181. Also, being bonded directly to the
surface of the member 181 or protective reinforcement 183, the reinforcement 185
can exhibit a reinforcement effect at small strain. The protective reinforcement
183 assumes, as needed, a function for transmitting a shear force induced between
the surface of the member 181 and the reinforcement 185. For example, a resin
primer is used as the protective reinforcement 183.
The reinforcement 185 and the reinforcement 187 may differ in a mechanism
for yielding a reinforcement effect so as to exhibit a reinforcement effect under
different load conditions and over the range of deformation. For example, there
are combined a method in which part of a shear force imposed on the member 181
is directly borne by a reinforcement, and a method in which the expansion of an
apparent volume of the member 181 is restrained.
Material and configuration of the reinforcement 187 can be such that a
reinforcement effect is yielded through restraint of the expansion of an apparent
volume. With the aim of enhancing the load bearing capacity of the member 181
through enhancement of shear fracture yield strength of the member 181, the
reinforcement 185 is made of an iron plate, carbon fiber, aramid fiber or the like.
Through direct transmission of a shear force between the member 181 and the
reinforcement 185, the shear force is shared between the member 181 and the
reinforcement 185, whereby the member 181 is reinforced. Also, a polyester sheet
or belt or the like whose rigidity is enhanced through impregnation with resin or
through application of adhesive to the entire surface thereof can be used as the
reinforcement 185. This yields a merit in that the reinforcement 185 and the
reinforcement 187 can be continuously laid.
FIG. 20 is a graph showing the relationship between load and deformation with
respect to the member 181 which is reinforced by means of a multilayer
configuration as shown in FIG. 19. In FIG. 20, the vertical axis represents load,
and the horizontal axis represents deformation. The load represents section
forces of the member 181, such as axial force, bending moment, shear force, etc.
The deformation represents deformations corresponding to the section forces;
specifically, axial contraction, flexural modulus, shearing strain, etc. A curve 193
which represents the case of reinforcement by means of multilayer configuration
indicates that the member 181 has load bearing capacity over a wider range of
deformation as compared to the case of no reinforcement employed as represented
by a curve 191.
FIG. 20 shows an ordinary example in which the effective deformation range of
the reinforcement 185 does not overlap with that of the reinforcement 187; i.e., a
slight reduction in load bearing capacity occurs between an effective range195 of
the reinforcement 185 and an effective range 197 of the reinforcement 187. The
reduction of load bearing capacity can be avoided by overlapping the effective
deformation ranges of the reinforcements 185 and 187.
According to this reinforced structure, reinforcements of different
characteristics are disposed in layers on the exterior of a member, to thereby exhibit
a reinforcement effect over a wide range of load conditions of the member as well
as over a wide range of conditions of the external environment. The member 181
is not limited to a concrete member or the like but may be the filler 147 shown in
FIGS. 17 and 18. In this case, through employment of the filler 147 that yields an
effect equivalent to that yielded by the protective reinforcement 183, the protective
reinforcement 183 may be omitted.
Notably, a beltlike reinforcement of high strength and rigidity, such as the
polyester belt 199, can be used as the reinforcement 185 to be bonded directly to
the surface of the member 181 or protective reinforcement 183. Since the
polyester belt 199 can be woven into texture that exhibits greater Young's modulus
per unit width as compared with a polyester sheet, the polyester belt 199 can be
used as the reinforcement 185, which exhibits a reinforcement effect at the stage of
small strain. For example, according to the tensile test result of the polyester belt
199 having a width of 64 mm and a thickness of 4 mm, strain is 2% under a load of
2500 kgf.
When the polyester belt 199 is used as the reinforcement 185, a column 205
shown in FIGS. 22 to 25 corresponds to the member 181 of FIG 19. A
reinforcement method by use of the polyester belt 199 as shown in FIGS. 22 to 25
will be described in the subsequent section of an eighth embodiment.
FIG 21 is a plan view of the polyester belt 199; FIGS. 22 and 23 are
perspective views showing examples of the column 205 reinforced by use of a
beltlike reinforcement 201; and FIG 24 is an elevation of the column 205 shown in
FIG 23.
First, reinforcement shown in FIG 22 will be described. In FIG 22, a plurality
of beltlike reinforcements 201 are disposed at predetermined intervals on the
column 205 in such a manner as to be wound about the column 205. End portions
of each of the beltlike reinforcements 201, which are wound about the column 205,
can be connected together by means of bonding and/or a clasp, which are
mechanical joints. Use of mechanical joints can implement reinforcement in a
short period of time and is thus suited for urgent reinforcement to be performed
immediately after an earthquake disaster. Beltlike reinforcements 203 bonded
axially to the column 205 can be expected to yield the effect of controlling a crack(s)
extending along a direction intersecting the same.
Next, reinforcement shown in FIGS. 23 and 24 will be described. The beltlike
reinforcement 201 is compactly wound about the column 205 shown in FIGS. 23
and 24. While tension is imposed on the beltlike reinforcement 201 in the direction
of arrow C, the beltlike reinforcement 201 is wound onto the column 205 in the
direction of arrow D, thereby enhancing a reinforcement effect. The beltlike
reinforcement 201 is bonded directly to the column 205. Comer portions of the
column 205 are not particularly required to be chamfered or to undergo like
processing in order to avoid breaking textile at the comer portions. However, a
beltlike reinforcement (not shown) bonded to a comer portion of a member in
parallel with the edge of the comer portion can be expected to yield the effect of
easing stress concentration of an edge portion on a reinforcement.
As shown in FIG. 24, the beltlike reinforcement 201 is wound onto an upper
end portion 207 and lower end portion 211 of the column 205 in parallel with the
circumferential direction of the column 205 and is spirally wound onto a general
portion 209 such that, as the beltlike reinforcement 201 is wound one turn, it axially
advances by the width thereof, whereby the beltlike reinforcement 201 can be
wound about the column 205 compactly and evenly. Also, the winding direction
(clockwise or counterclockwise) can be altered so as to wind the beltlike
reinforcement 201 onto the column 205 in two layers, three layers, etc., thereby
enhancing a reinforcement effect. In this case, after winding of the first layer is
completed, an adhesive is applied to the first layer, and then the second layer is
formed through winding such that the winding pitch is shifted by half the width of the
beltlike reinforcement 201 between the first and second layers, thereby preventing
the potential move of the beltlike reinforcement 201.
In order to allow the reinforcing member to be in close contact with the
substrate in the above winging manner, it is required that the reinforcing member
can be bent at an angle equal to or greater than the comer angle of the column, and
sheared at an angle equal to or greater than the displacement angle between the
parallel winding and the spiral winding. In a typical column, the bending angle and
the displacement angle are 90-degree or less and 2-degree or less, respectively.
When a reinforcing member is installed in a crossed manner as described later in
connection with FIG. 56, it is preferable that the reinforcing member can be sheared
at a large angle.
FIG. 25 is a sectional view of a surface portion of the column 205 shown in
FIGS. 22 to 24. As shown in FIG. 25, the beltlike reinforcement 201 is bonded
directly to the column 205 by use of an adhesive 213.
The beltlike reinforcement 201 shown in FIGS. 22 to 25 is, for example, the
polyester belt 199 shown in FIG. 21. As mentioned in the sections of the second
and seventh embodiments, the polyester belt 199 is made of polyester fiber, which
is a material for a strap or the like. The polyester belt 199 is used particularly in
view of the following: being higher in rigidity and strength than a civil engineering
sheet, the polyester belt 199 restrains an increase in the width of crack in the
column 205 and controls the deformation of an apparent volume for the range of
small strain.
Next will be described the method for calculating the amount of reinforcement
in the case of reinforcement for restraining the width of crack for the range of small
strain of the column 205. FIG. 26 is a view showing an effective bond length
between the beltlike reinforcement 201 and a crack 215.
When a member is locally ruptured due to bending, axial force, shear force, or
a like force imposed thereon, the crack 215 appears on the surface of the member.
In FIG. 26, the crack 215 is made on the surface of the column 205, to which the
beltlike reinforcement 201 is bonded directly. The belt width 219 of the beltlike
reinforcement 201 is w. A force which attempts to expand the crack 215; i.e.,
tension 221, is imposed on the beltlike reinforcement 201 in the amount of q per belt.
In FIG. 45, the beltlike reinforcement 201 restrains crack width 217 to d or less.
Stress concentration is present in the vicinity of the crack 215. Width 223 (a)
extending in opposite directions from the crack 215 is the length of a region where a
bonding effect is lost due to shear fracture of the adhesive 213 or member surface.
Width 223 (a) is hereinafter called a free length. Restraint length 225 (b) is a
natural restraint length of the column 205 and is measured from a free end.
Accordingly, the beltlike reinforcement 201 is bonded to the column 205 along
fixation length s = b - a.
Restraint length 225 is the length of a single side in the case a rectangular
cross section, as in the column 205, and is the length of an arc corresponding to a
central angle of about 90 degrees in the case of a circular cross section. When
these lengths are significantly large as compared with belt width 219 (w) of the
beltlike reinforcement 201, restraint length 225 is a length along which an effective
bonding force is not zero.
When the crack 215 is located at around the center of a certain surface of a
member having a rectangular cross section, restraint length 225 extends to another
surface of the member.
When k represents the rigidity of the beltlike reinforcement 201, free length a;
i.e., width 223, crack width 217 (d), and tension 221 (q) are related as expressed
by
q = kd/a
when τ represents the average shear force between the beltlike reinforcement
201 and the column 205 as measured within fixation length s = b-a, τ is expressed
by
τ = q/(w·s)
When free length a is eliminated from Eq. 21) and Eq. 22), tension 221 (q),
average shear force τ, and crack width 217 (d) hold quadratic relation as
represented by
q = 1/2[τwb ± {(τwb)2 - 4τwkd}0.5 ]
This relation has two solutions q at maximum crack width dmax or less. Since
a larger solution is first realized, the larger solution is employed. Then, q falls
somewhere between maximum value qmax and minimum value qmin according to
crack width 217 (d).
qmax = τwb
qmin = 0.5τwb
Crack width dmax corresponding to minimum value qmin is expressed by
dmax = τwb2 /(4k)
When the crack width is in excess of dmax, Eq. 23) does not have a solution.
That is, such a mechanism does not hold true. Maximum value qmax and minimum
value qmin when the beltlike reinforcement 201 bears part of a force attempting to
expand the crack 215 are obtained from the above relations, thereby enabling
design of structural reinforcement through utilization of the above-mentioned
mechanism. Values obtained from Eq. 24) to Eq. 26) are proportional to bonding
force τ (average shear force) between a member, such as the column 205, and the
beltlike reinforcement 201.
When a material which is inexpensive and has excellent stretchability, such as
the polyester belt 199, is used as the beltlike reinforcement 201, since the Young's
modulus of the material is about one-tenth that of concrete or one-hundredth that of
iron, the following problem is involved. Even when the adhesive 213 having large
average shear force τ is used for bonding, the material encounters difficulty in
sharing with a member a force which is elastically imposed on the member, without
formation of the crack 215. However, when a reinforcement effect is particularly
needed at the stage of small deformation, a polyester belt or the like is impregnated
with resin to thereby enhance the rigidity of the reinforcement. The thus-prepared
reinforcement is used together with an epoxy resin adhesive.
The polyester belt 199 has a woven body of a weft double weave using a
polyester-fiber yam with 1700 dtex (dcitex). The polyester belt 199 has a Young's
modulus of 4676 MPa, a thickness of 4 mm, a fracture strain of 15%, and a specific
gravity of 0.98. Since the polyester base yam has a specific gravity of 1.4, a void
ratio of the polyester belt 199 is (1.4/0.98=) 1.43 when expressed by the ratio of
specific gravity.
The column 205 is made of reinforced concrete. Concrete has a compression
fracture strength of 13.8 MPa (135 kgf/cm2), a Young's modus of 19500 MPa, and a
direct shear strength of about 2.6 MPa. The reinforcing member was installed
without performing any chamfering and any adjustment of surface unevenness.
Rubiron 101 (one-component: available from Toyo Polymer Co.) was used as
an adhesive. The layer of the adhesive is 1 mm. The adhesive has a bonding
strength of about 1 MPa (10 kgf/cm2), and a specific gravity of 1.4. A part of the
adhesive is infiltrated into the texture of the polyester belt 199, and cured.
However, even if the entire adhesive of 1 mm thickness enters into the void of the
polyester belt 199, it will occupy only about 70% of the void of the polyester belt 199,
and the breathability or air-permeability of the reinforcing member can be
maintained. While Rubiron 101 is not a non-solvent adhesive, it has been
experimentally verified that the same reinforcement effect can be obtained even
using a non-solvent adhesive having a bonding strength equivalent to that of
Rubiron 101.
With respect to the effect of the reinforcement using the impregnated aramid
fibers as disclosed in the aforementioned Japanese Patent Laid-Open Publication
No. 8-260715, a test result of the same method as that in FIG. 29 is introduced in a
number of publications. However, none of these publications reports the increase
of load after Qmin, as indicated by the load-deformation curve 243 b in FIGS. 30 and
50, and the test ends up with the fracture of the aramid-fiber reinforcing member
before Q min or the peeling of the reinforcing member from a structure member.
A case study is conducted for the structure of FIG. 25 under, for example, the
following conditions: the beltlike reinforcement 201 is the polyester belt 199 having
a width of 64 mm and a thickness of 4 mm; the column 205 is a reinforced-concrete
column having a restraint length 225 of b = 30 cm; and the adhesive 213 is
LUBIRON, which is the trade name of an epoxy urethane adhesive produced by
Toyo Polymer Corp. In this study, calculation conditions are as follows: average
shear force τ = 10 kgf/cm2; the beltlike reinforcement 201 (polyester belt 199) has a
belt width 219 of w = 6.4 cm and a restraint length 225 of b = 30 cm; and the beltlike
reinforcement 201 (polyester belt 199) has a rigidity of k = 153000 kgf/cm2.
Calculation of maximum value qmax, minimum value qmin, and maximum crack
width dmax by use of Eq. 4) to Eq. 6) gives the following results: maximum value qmax
= 1920 kgf; minimum value qmin = 960 kgf; and maximum crack width dmax = 0.12
cm.
Accordingly, when this reinforcement is carried out, cracking can be restrained
up to maximum crack width dmax = 1.2 mm. A single beltlike reinforcement 201
(polyester belt 199) bears a tension 221 of q = 0.9 tf.
FIG. 27 is a schematic view of the column 205 subjected to an axial force,
bending, and a shear force. FIG. 28 is a view showing a force which attempts to
expand the crack 215 formed in the column 205. Described below is a
reinforcement effect to be yielded in the case where the column 205 is reinforced by
use of the polyester belt 199, which serves as the beltlike reinforcement 201,
according to the method of FIG. 24; and the thus-reinforced column 205 is loaded in
the following manner: while axial force 229 (P) is applied to the column 205, a
horizontal force is applied to the column 205 so as to repeatedly generate bending
moment 231 (M) and shear force Q.
The column 205 is assumed to be an ordinary structural column. Conditions
of study are as follows: shear force 227 (Q) is horizontally imposed on the column
205 at the middle of height h; i.e., at height (h/2); and the upper and lower ends of
the column 205 slide horizontally without involvement of rotation. As a result, a
horizontally even shear force (resultant force Q) and an axial force (resultant force
P) are generated in the column 205. A bending moment is M=Qh/2 at the upper
end of the column 205, zero at the middle, and -M at the lower end.
When shear force 227 (Q) reaches maximum shear force Qmax, which depends
on the conditions of reinforcing bars and concrete of the column 205, the crack 215
is generated in a direction of angle 237. A force which attempts to horizontally
expand the crack 215 is shear force 227 (Q) imposed on the column 205. The
force is considered to be borne by the beltlike reinforcement 201 which is present
over the range represented by arrow c 233. Since a single belt of the beltlike
reinforcement 201 has a width of w and exhibits a tension of q, a resultant force Q
of the beltlike reinforcement 201 present over the range represented by arrow c 233
is represented by Q = q·2C/w.
Since the column 205 has a rectangular cross section, the beltlike
reinforcement 201 on the near-side surface thereof and that on the far-side surface
thereof are involved in reinforcement; therefore, a coefficient of 2 is used. As seen
from FIG. 28, length C of arrow c 233 is represented by C = btan. Generally,
shear force Q is partially borne by a member. However, it is assumed that, when
the deformation of the member exceeds a level corresponding to around Qmax, at
which a belt becomes significantly effective, substantially the entire shear force is
borne by belt tension.
When angle 237 is 45 degrees, width 235 of the column 205 is b (restraint
length) = 30 cm. Accordingly, horizontal forces Qmax and Qmin corresponding to
maximum value qmax and minimum value qmin which are previously calculated for
the polyester belt 199 (width 64 mm and thickness 4 mm) by use of Eq. 24) to Eq.
26) are obtained as Qmax = qmax2b/w = 18000 kgf and Qmin = qmin2b/w = 9000 kgf.
Thus, by virtue of the effect of the reinforcement, a horizontal resistance force of not
less than 9 tf can be maintained when the width of the crack 215 is not in excess of
dmax = 1.2 mm.
Next will be described the results of a test conducted in the following manner: a
horizontal force was repeatedly applied to an unreinforced column 205 and to a
column 205 reinforced by use of the polyester belt 199 (width 64 mm and thickness
4 mm), which serves as the beltlike reinforcement 201 shown in FIG. 24, under the
conditions of FIG. 27 while displacement was controlled. Other test conditions
were as follows: the concrete strength of the column 205 is 135 kgf/cm2; the axial
ratio of reinforcement is 0.56%; the ratio of shear reinforcing bar is 0.08%; an axial
force is held constant at 37 tf (axial force ratio 0.3).
FIG. 29 is a schematic view showing the deformation of the column 205.
FIGS. 30 to 35 show experiment results, in which horizontal displacement δh 239
represents the horizontal displacement of the column 205; and vertical
displacement δv 241 represents the vertical displacement of the column 205. FIG.
30 is a graph showing the relationship between horizontal force Q of the column
205 and an envelope indicative of displacement hysteresis of the column 205. FIG.
31 is a graph showing the relationship among the horizontal displacement of the
column 205, the vertical displacement of the column 205, and a horizontal force.
FIG. 32 is a graph showing restoring-force characteristics of the column 205.
In FIG. 30, the horizontal axis represents horizontal displacement δh (239) of
the column 205, and the vertical axis represents horizontal force Q (shear force
227). In FIG. 32, the horizontal axes represent horizontal displacement δh (239) of
the column 205 and the angle of deformation, and the vertical axis represents
horizontal force Q (shear force 227).
In FIG. 30, a reinforcement-absent curve 243a is an envelope as observed
when the column 205 is not reinforced with the beltlike reinforcement 201, and a
reinforcement-present curve 243b is an envelope as observed when the column
205 is reinforced. The reinforcement-present curve 243b is an envelope along the
following points on a hysteretic loop 253 shown in FIG 32: a point corresponding to
a level 255a equivalent to the level of the Great Hanshin Earthquake Disaster, a
point corresponding to a level 255b equivalent to two times the level of the Great
Hanshin Earthquake Disaster, a point corresponding to a level 255c equivalent to
three times the level of the Great Hanshin Earthquake Disaster, a point
corresponding to a level 255d equivalent to five times the level of the Great Hanshin
Earthquake Disaster, etc.
In FIG. 31, the horizontal axis represents horizontal displacement δh (239); the
upward vertical axis represents horizontal force Q (shear force 227); and the
downward vertical axis represents vertical displacement δv (241). A
reinforcement-absent curve 243a and a reinforcement-present curve 243b are
envelopes similar to those shown in FIG. 30. The reinforcement-absent curve
245a shows vertical displacement δv of the column 205 which is not reinforced with
a beltlike reinforcement. The reinforcement-present curve 245b shows vertical
displacement δv of the column 205 which is reinforced with the beltlike
reinforcement 201 (polyester belt 199).
As shown in FIGS. 30 and 31, when Qmax1 represents the maximum horizontal
force in the case of no reinforcement being employed as represented by the
reinforcement-absent curve 243a; Qmax2 represents the maximum horizontal force in
the case of reinforcement being employed as represented by the
reinforcement-present curve 243b; and Qmin represents the minimum horizontal
force in the case of reinforcement being employed as represented by the
reinforcement-present curve 243b, experiment data show Qmax1 = 17.5 tf, Qmax2 = 18
tf, and Qmin = 7 tf.
In FIG. 31, the reinforcement-absent curve 243a, which shows horizontal force
Q of the unreinforced column 205, and the reinforcement-absent curve 245a, which
shows vertical displacement δv, drop sharply at and after the time when horizontal
force Q becomes Qmax1. This supports the aforementioned assumption that, in the
case of the reinforced column 205, the beltlike reinforcement 201 (polyester belt
199) exhibits a reinforcement effect; i.e., the beltlike reinforcement 201 bears
substantially the entire shear force in a horizontal-displacement region ranging from
a horizontal displacement corresponding to Qmax2 to a horizontal displacement
corresponding to Qmin.
The experimentally obtained value of minimum horizontal force Qmin appearing
on the reinforcement-present curve 243b is lower than a calculated value of 9 tf,
which is obtained through calculation using the models of FIGS. 27 and 28. This
can be said to be an experimental error and implies the occurrence of a drop in
strength at the bond area between the concrete surface of the column 205 and the
beltlike reinforcement 201 (polyester belt 199). The value of maximum shear force
Qmax2 is substantially equal to a calculated value of 18 tf.
As shown in FIG. 29, when horizontal displacement δh of the column 205 is
displacement amplitude δhc 247, the reinforcement-present curve 243b indicative of
horizontal force Q has a horizontal-force inflection point 249, and the
reinforcement-present curve 245b indicative of vertical displacement δv has a
vertical-displacement inflection point 251. Displacement amplitude δhc 247 is
horizontal displacement δh at around a point corresponding to the level 255c
equivalent to three times the level of the Hyogo-Ken Nanbu Earthquake on the
hysteretic loop 253 shown in FIG. 32; i.e., about 140 mm (angle of deformation 0.15
rad).
FIG. 33 is a graph showing the relationship between cumulative horizontal
displacement Σδh and hysteretic absorbed energy W in the column 205. FIG 34 is
a detailed view of FIG 33. In FIG 33, the horizontal axis represents cumulative
horizontal displacement Σδh, and the vertical axis represents hysteretic absorbed
energy W.
Cumulative horizontal displacement Σδh, which is represented by the horizontal
axis in FIGS. 33 and 34, was calculated by the equation shown below. In the
equation, i is the number of steps in data recording, and n is the current number of
steps. Cumulative horizontal displacement Σδh is calculated as an indicator of a
position on the hysteretic loop 253 shown in FIG 51.
Cumulative absorbed energy W represented by the vertical axis was
calculated by the following equation. Cumulative absorbed energy W is work done
by horizontal force Q; i.e., by shear force 227.
W = ∫Qd δ h
When a certain column 205 of a structure bears an axial force 229 of P,
corresponding mass m can be represented by use of gravitational acceleration g as
m = P/g. Thus, of energy which is input to the structure and consumed until
completion of vibration, work E which is done by shear force 227 imposed on the
column 205 is approximated by the following expression by use of velocity response
spectrum Sv of earthquake motion.
E = 0.5(P/g)Sv2
The curve of hysteretic absorbed energy 257 shown in FIG. 33 shows
hysteretic absorbed energy which is calculated from the experimentally obtained
hysteretic loop 253 shown in FIG. 51, by use of Eq. 28). The straight lines
indicative of a level 259a equivalent to the level of the Great Hanshin Earthquake
Disaster and a level 259b equivalent to five times the level of the Great Hanshin
Earthquake Disaster represent values which are calculated by Eq. 29) for
comparison with the curve of hysteretic absorbed energy 257. FIG 53 additionally
show values which are calculated by Eq. 29) and represented by the straight lines
indicative of a level 259c equivalent to two times the level of the Great Hanshin
Earthquake Disaster and a level 259d equivalent to three times the level of the
Great Hanshin Earthquake Disaster. Velocity response spectrum used in the
calculation by Eq. 29) was Sv = 90 cm/s at a natural period of 0.3 sec appearing in
the record of Kobe Marine Meteorological Observatory.
FIG. 35 is a graph showing the relationship between calculated cumulative
horizontal displacement Σδh and vertical displacement δv by use of Eq. 27). In FIG.
35, the horizontal axis represents cumulative horizontal displacement Σδh, and the
vertical axis represents vertical displacement δv (241 ). As mentioned previously in
the description which was given with reference to FIG. 31, when horizontal
displacement is horizontal amplitude δhc 247; i.e., about 140 mm, the
vertical-displacement inflection point 251 appears. At this time, cumulative
horizontal displacement Σδh is about 1500 mm. As shown in FIG. 35, vertical
displacement δv is not greater than 5 mm (strain 0.5%) until cumulative
displacement reaches about 1500 mm at the vertical-displacement inflection point
251.
The above-described experiment demonstrated the following:
As seen from the results of experiment shown in FIGS. 30 to 35, in which the
beltlike reinforcement 201, such as the polyester belt 199, is bonded directly to a
member, such as the column 205, exhibits continuously a reinforcement effect on
deformation ranging from a small one as observed after formation of the crack 215
to a large one.
A conventional reinforcement method in which a member is wrapped with
reinforcement is characterized in that, in order to prevent formation of cracks, a
reinforcement material, such as carbon fiber or wrapping iron plate, having rigidity
equivalent to or greater than that of a major dynamic component of the member is
bonded directly to the surface of the member by use of resin or the like. The
beltlike reinforcement 201, such as the polyester belt 199, is bonded directly to a
member, such as the column 205 is not adapted to suppress formation of the crack
215 on the member surface but is adapted to restrain crack width 217 to an effective
value; for example, to about 2 mm, whereby the functional impairment of a member
is controlled to thereby maintain usability and safety of a structure.
A method in which a high-rigidity material, such as the polyester belt 199, is
bonded directly to the surface of a member is intended to enhance the effect of
maintaining the shape of the member with respect to deformation accompanied by
finite crack 215. As seen from Eq. 21) to Eq. 24), this effect is enhanced in
proportion to the circumferential rigidity of a reinforcement, and the enhancement of
the effect is limited by the magnitude of a shear force to be transmitted between the
surface of the member and the reinforcement. Accordingly, through a high-rigidity
reinforcement being bonded directly to a member, a reinforcement effect can be
enhanced.
The beltlike reinforcement 201 used in the ninth embodiment is not limited to
the polyester belt 199. Any material having strength and rigidity equivalent to
those of the polyester belt 199 can be used.
The reinforcement method is such that, through control of an increase in crack
width 217, the expansion of an apparent volume of a member is restrained. Thus,
in principle, the method is identical to that of the previous application. However,
the method employs the mechanism of restraining variation in shape and axial
strain and is verified theoretically and experimentally, thereby indicating high
practical viability thereof.
Next, a structure for enhancing a reinforcement effect for a member involving
an irregular profile and a member-to-member joint of the present invention will be
described. FIG. 36 is a perspective view showing a state in which connecting
reinforcements 269a and 269b are disposed on the joint between a column 261 and
a beam 263. The beam 263 is joined to the column 261 at right-hand and left-hand
side surfaces 265b.
The joint between the column 261 and the beam 263 is reinforced by use of
two sheetlike connecting reinforcements 269a and four connecting reinforcements
269b. The connecting reinforcement 269a assumes the form of a sheet and is
bonded to the column 261 and the beam 263 in such a manner as to cover the
joints between the side surfaces 265b of the column 261 and the side surface 267a
of the beam 263. A central portion of the connecting reinforcement 269a is
bonded to a side surface 265a of the column 261 and the right-hand and left-hand
side surfaces 265b adjacent to the side surface 265a. Opposite end portions of
the connecting reinforcement 269a are bonded to the side surface 267a of the
beam 263.
The connecting reinforcement 269a assumes the form of a sheet and is
bonded to the column 261 and the beam 263 in such a manner as to cover the joint
between the side surface 265b of the column 261 and the side surface 267b of the
beam 263. The connecting reinforcements 269a and 269b are, for example,
stretchable, fibrous or rubber sheet materials.
The connecting reinforcements 269a and 269b are not necessarily sheetlike
reinforcements but may assume the form of a beltlike reinforcement, such as the
polyester belt 199. The thickness, width, length, etc. of the connecting
reinforcements 269a and 269b, either sheetlike or beltlike, are determined to
provide a required amount of reinforcement.
The connecting reinforcements 269a and 269b may be bonded to the column
261 and the beam 263 in a tentative condition but may be bonded in such a manner
as to yield strength. Generally, the displacement amplitude of a structure depends
greatly on the deformation of a member-to-member joint. Thus, in view of the
amount of reinforcement being determined by the method shown in step 309 of FIG.
40, which will be described later, use of the latter bonding is practical.
FIG. 37 is a perspective view showing a state in which a beltlike
reinforcements 271a and 271b are disposed on the joint between the column 261
and the beam 263. In FIG. 37, a single beltlike reinforcement 271a and two
beltlike reinforcements 271b are disposed in such a manner as to cover the
connecting reinforcements 269a and 269b which are disposed as shown in FIG. 36.
The beltlike reinforcement 271a is disposed on the exterior of a bigger member; i.e.,
on the exterior of the column 261. The beltlike reinforcement 271a is wound onto
the column 261 in such a manner as to be continuously wound between a portion of
the column 261 located above the joint between the column 261 and the beam 263
and a portion of the column 261 located below the joint while obliquely crossing the
joint. The beltlike reinforcement 271b is disposed on the exterior of a thinner
member; i.e., on the exterior of the beam 263. The beltlike reinforcement 271b is
independently wound about the right-hand and left-hand beams 263 joined to the
column 261.
The above-described method is repeatedly carried out until a required amount
of reinforcement is obtained. In FIG. 37, the beltlike reinforcements 271a and
271b are disposed in two layers and cross-wound onto the joint between the
column 261 and the beam 263.
The beltlike reinforcements 271a and 271b are bonded to the column 261 and
the beam 263 in such a manner as to yield strength. FIG. 38 is a sectional view of
the joint between the column 261 and the beam 263 on which the connecting
reinforcements 269b, etc. are disposed. The beltlike reinforcements 271a and
271b are disposed on the connecting reinforcement 269b in a winding condition.
The column 261 or the beam 263 and the sheetlike connecting reinforcement 269b
are bonded such that tension is mutually transmitted via shear resistance of a bond
zone. Similarly are bonded the following combinations: the connecting
reinforcement 269b and the beltlike reinforcements 271a and 271b; the column 261
or the beam 263 and the connecting reinforcement 269a; and the connecting
reinforcement 269a and the beltlike reinforcements 271a and 271b.
In case of need, a reinforcement 273a is wound about the exterior of the
column 261, and a reinforcement 273b is wound about the exterior of the beam 263.
The reinforcements 273a and 273b are stretchable sheetlike or beltlike materials.
As described above, according to the reinforced structure, the connecting
reinforcements 269a and 269b are disposed on the joint between the column 261
and the beam 263 so as to enhance a member-to-member reinforcement effect.
Furthermore, the beltlike reinforcement 271a is cross-wound onto a joint of a bigger
member, i. e., about a joint of the column 261, and the beltlike reinforcements 271a
and 271b are wound about the exterior of the column 261 and that of the beam 263
in layers, to thereby obtain a required amount of reinforcement.
In FIGS. 36 and 37, the reinforcement is cross-wound onto the joint. However,
the reinforcement can be wound about the joint in the form of the letter T or the like.
Reinforcement is applicable not only to the joint between a column and a beam but
also to the joint between other members. The method can be combined with the
method using slits or bores. This combined method is particularly effective for
reinforcing the joint between members of greatly different thicknesses or shapes,
such as the joint between a slab and a beam or the joint between a wall and a
beam.
When a sufficient amount of reinforcement can be obtained merely by use of
the beltlike reinforcements 271a and 271b, the connecting reinforcements 269a and
269b can be omitted.
In the above reinforced structure of a structural body, the reinforcing member is
made of a material having high ductility and high bendability, or extensibility, and
installed on the surface of or inside a structure member or substrate through the
fixation using an adhesive, so as to constrain the apparent volume expansion of the
structure member to control the change in shape or the damage of the structure
member.
A material which is inexpensive and facilitates working and bonding, such as a
polyester sheet, is used as a reinforcement material. The Young's modulus of
such a material is about one-tenth that of concrete or one-hundredth that of iron.
Thus, the reinforcement material's effect of bearing part of a load imposed on a
member during the elastic stage accompanied by very small strain as do reinforcing
bars of reinforced concrete, is very weak; specifically, as weak as the
above-mentioned Young's modulus ratios.
However, when repeated imposition of load induces yielding and cracking of
main component materials, such as concrete and iron, of a column; i.e., when
plastic deformation begins, the rigidity of the member drops; thus, the method of the
previous application exhibits significant effectiveness. Even after concrete or a like
component material of the column assumes a granular form and then a powder
form, and iron undergoes significant plastic deformation or ruptures retains these
component materials in a unitary shape, thereby exhibiting the capability of
maintaining an axial force and the capability of resisting an external force, such as
bending and shearing.
The reinforced member absorbs very large energy in the above-mentioned
sequential repeated-deformation process while maintaining rigidity, thereby
preventing the collapse of a structure which would otherwise result from reception
of an abrupt external force, such as a seismic force.
FIG. 41 is a diagram showing the relationship between cumulative deformation
and hysteretic absorbed energy with respect to a reinforced member on which a
repeated load is imposed. The horizontal axis represents cumulative deformation,
and the vertical axis represents hysteretic absorbed energy. As a result of a
repeated external force being imposed on a member during the member being
deformed with involvement of finite cracking, component materials of the member
are partially ruptured. A shear force transmitted between the member and a
reinforcement decreases accordingly. As a result, a reinforcement effect weakens,
and the effect of retaining the shape of the member also weakens. The rupture of
component materials of the member induced as a result of reception of a repeated
load can be measured in terms of work done by the external force; i.e., in terms of
hysteretic absorbed energy.
A certain limit (called a shape retainment limit energy 275) is present according
to the type and amount of material. When this limit is exceeded, a material
behaves in a granular fashion, and thus the shape of a member begins to vary
significantly. A member reinforced according to a method of the present invention
or the previous application is deformed such that the cross section assumes a
circular shape, and the entire shape approaches to the shape of linked balls.
Accordingly, the shape of a structure also varies significantly.
The method of the present application is characterized by being able to cope
with a wide energy region and a wide deformation region, and an enhancement of
an effect to be yielded as shown in FIG. 41. When the method of the present
invention are applied to a seismic isolator, the seismic isolator can absorb energy in
such an amount that a material having a volume equivalent to that of the seismic
isolator is pulverized substantially completely, while variation in shape is minimized,
and rigidity is retained. This is a very efficient behavior for a seismic isolator.
When a special filler is mixed into a component material of a seismic isolator, the
filler functions to internally reinforce the material through utilization of energy, such
as heat, to be generated by work which is done by an external force in the
above-mentioned process, thereby further enhancing a seismic isolation effect.
Next, the fibrous sheetlike reinforcements and beltlike reinforcements as
mentioned above are impregnated with resin will be described. FIG. 42 is a graph
showing the relationship between tensile stress and strain with respect to a
reinforcement material impregnated with resin and a reinforcement material
unimpregnated with resin. The vertical axis represents tension, and the horizontal
axis represents extensional strain (%).
An impregnated-with-resin curve 277 shows the stress-strain relation obtained
from a tensile test which was conducted on a polyester sheetlike textile
impregnated with epoxy resin after the resin was cured. An
unimpregnated-with-resin curve 279 shows the stress-strain relation obtained from
a tensile test which was conducted on the same sheetlike textile unimpregnated
with epoxy resin.
Comparison in FIG. 42 between the impregnated-with-resin curve 277 and the
unimpregnated-with-resin curve 279 shows the following: as a result of
impregnation with resin, rigidity; i.e., the gradient of the parting line of the graph, is
significantly large at a strain of 0% to about 3%; and deformation can be maintained
without rupture until large strain is reached. Similar test results are also obtained
from a polyester beltlike material, such as the polyester belt 199 shown in FIG. 21.
The test results shown in FIG. 42 show the following: as a result of a sheet or
beltlike material woven from polyester fiber being impregnated with resin, resin
yields the effect of restraining deformation of fiber for the range of small strain; thus,
the material represented by the impregnated-with-resin curve 277 exhibits
increased rigidity as compared with the material represented by the
unimpregnated-with-resin curve 279. When deformation increases, the material
represented by the impregnated-with-resin curve 277 loses the above-mentioned
effect without significant breakage of fiber. As a result, deformation can be
maintained until a large strain of not less than 15% is reached.
Thus, through a reinforcement material impregnated with resin; i.e., a material
of a single kind, enhances the effect of restraining deformation for the range of
small strain as well as yields the effect of bearing a load for the range of large strain.
The aforementioned reinforcing member can be designed as follows.
As described above, the dynamic property (the relationship between external
force and deformation) of the reinforced structure is defined by the following
parameters. Thus, the reinforced structure can be designed by calculating the
performance of a structural body subject to reinforcement, according to these
parameters and data of the structural body.
1) | Thickness of reinforcing member | t |
2) | Young's modulus of reinforcing member | Ef |
3) | Fracture strain of reinforcing member | εfb |
4) | Reinforcing-member stress at yield of fixation structure | σfmax |
5) | Reinforcing-member installation mode | |
(Whether reinforcing-member is closingly looped (FIG. 1) or not (FIG. 3)) | ||
6) | Reinforcing-member installation range | |
(When not closingly looped) expressed by | b | |
7) | Peeling-limit elongation | δ1 |
For determination of reinforcing-member stress at yield of fixation structure, the following 8) or 9) can be used. | ||
8) | Constraint length b and Average fixation strength | τf |
9) | Peeling energy of boundary surface of fixation structure | Gf |
Further, the gap width and reinforcing-member tensile force in a
SRF-reinforced structure has a relationship as shown in FIG. 44. Specifically, if
the gap width is increased from zero, a reinforcing member will be elongated in a
fixation zone, and thereby a reinforcing-member stress will be generate. When the
elongation of the reinforcing member on the gap reaches δ1, the release of the
fixation structure is initiated to generate a free length a (FIG. 44). If the fixation is
based on bonding, and the reinforcing member is bonded even at a position
sufficiently away from the gap, the fixation force will be kept at an approximately
constant value as long as a constraint length (the distance between the gap and a
position where the fixation force is not zero) can be increased in conjunction with
the increase of the gap width (FIG. 4). This is the range from Point A to Point B in
FIG. 44. Subsequently, a fixation length (s = b - a) is reduced, and thus the
reinforcing-member stress is reduced. This is the range from Point B to Point C.
According to the theory shown in the expressions [1] to [4], the bonding is released
all at once when the reinforcing-member stress becomes half of its maximum value.
If the reinforcing member is closingly looped, or a geometrical constraint exists at
the comer of the structure member or the like, the fixation force will be maintained
to increase a reinforcing-member tensile force in proportion to the gap width until
the reinforcing member reaches a fracture stress (stress corresponding to the
fracture strain ε fb) (range from Point C to Point D).
For example, in case of a bar-shaped structure member, the relationship
between reinforcing-member tensile force and restoring force can be determined
from the theory as shown in the expressions [9] and [10], or an experimental test.
Further, the reinforcing-member elongation δ1 providing the maximum value of the
reinforcing-member tensile force is a value derived from integrating strains in the
fixation zone of the reinforcing member at the time of the limit where the bonding is
released (when the reinforcing-member tensile force reaches σ fmax), and becomes
smaller as the Young's modulus of the reinforcing member is increased. This
factor is ignored in the theory shown in the expressions [1] to [4].
The maximum reinforcing-member tensile force may be derived from dividing
the product of the restraint length and the average bonding strength by the
reinforcing-member thickness from the expression [4]. However, if the reinforcing
member is wounded around a structure member, and the structure member is
installed over a wide range, the constraint length cannot be figured out in some
cases. This problem can be solved by determining the maximum
reinforcing-member tensile force using the boundary-surface peeling energy in the
following expression [101]:
σ f max = 2Ef Gf t
The boundary-surface peeling energy is defined as energy required for peeling
the bonding boundary-surface of unit area between a thin elastic body and a
substrate as shown in FIG. 44, and can be calculated from the following expression
[102] using the maximum tensile force σ fmax caused in the elastic body and the
thickness t and Young's modulus of the elastic body, which are obtained as the
result of a peeling test.
Gf = t 2Ef σ2 f max
The expression [101] is obtained by resolving the formula [102] about σ fmax.
In a design for SRF-reinforcing a reinforced concrete structure member, a
conventional design formula for reinforced concrete structure members can be
applied to the calculation of the reinforcement effect of a SRF reinforcing member
by substituting the SRF reinforcing member with a reinforcing bar and calculating
the reinforcement effect using the boundary-surface peeling energy etc. by use of
the phenomenon that a SRF reinforcing member apparently yields at σ fmax as
shown in FIG. 55 (expression [103]). However, there is possibility that the gap
width in the design limit state does not reach the peeling-limit elongation δ1
illustrated in FIGS. 44 and 55 due to a small Young's modulus of the SRF
reinforcing member as compared to that of reinforcing bar. Thus, it is required to
take notice of checking whether δ1 is caused within the design limit, through an
experimental test or the like, or putting a limit on the reinforcing-member stress.
For example, in a design for a SRF reinforcing member installed based on
bonding in such a manner that it is wounded around a bar-shaped reinforced
concrete structure member shown in FIG.7, an equivalent shear reinforcing bar
amount Pwf after reinforcement is calculated as follows:
Pwf = Pw + 2t σ f max bm σ sy
, wherein t is the thickness of the reinforcing member, bm being the width of the
section of the structure member, pw being the ratio of the shear reinforcing bar to
the structure member subject to reinforcement, and σ sy being a yield stress of the
reinforcing bar. Further, while a maximum reinforcing-member tensile force σ fmax
is calculated using the expression [101], it is given that the reinforcing-member
stress does not go beyond a value corresponding a reinforcing-member strain of
1%.
The above apparent yield stress (σfmax in the expressions [101] and [102]) is a
maximum stress capable of being borne before the fixation of the reinforcing
member is released (FIG. 45), and calculated from the Young's modulus of the
reinforcing member, the boundary-surface peeling energy and the thickness of the
reinforcing member using the expression [101]. In the expression [101], the
apparent yield stress is reduced in reverse proportion to the square root of the
thickness. Thus, the reinforcing-member thickness can be determined by a simple
repeated calculation.
As above, while the present invention has been described in conjunction with
preferred embodiments of a reinforced structure, reinforcing method,
quake-absorbing structure, and reinforcing member for a structural body according
to the present invention, the present invention is not limited to such embodiments.
It is obvious to those skilled in the art that various changes and modifications may
be made therein without departing from the spirit and scope of the present invention.
Therefore, it is intended that such changes and modifications are obviously
encompassed within the scope of the present invention.
As mentioned above, the present invention can provide a reinforcing material
or member excellent in ductility and load-withstanding capacity, quickly at a low cost.
The effects of the reinforcing member according to the present invention is effective
to repair, maintenance and reinforcement of existing structure bodies, and usable in
new structural bodies. In either case, the cost, construction period etc. required for
satisfying a desired performance can be reduced as compared to those in
conventional techniques. The reinforcing material or member according to the
present invention is useable as a safeguard against sudden external forces such as
explosion, which have been untreatable by conventional techniques. In addition,
the reinforcing member installed on the outer surface of a structure member as a
primary element thereof makes it possible to provide a reinforced structure readily
at a low cost and achieve enhanced reinforcement performance. Furthermore, the
present invention facilitates reuse of decrepit or affected structural bodies to
promote effective use of existing structural bodies and industrial resources and to
allow industrial wastes to be reduced.
Moreover, a reinforcement configuration, a seismic isolator, and a
reinforcement method for a structure according to the present invention can suitably
be applied to, for example, the following cases: a member to be reinforced involves
undulation or an irregular profile; a member is joined to or located in proximity to
another member or a nonstructural member; a reinforcement is possibly
deteriorated due to interaction between a member and the reinforcement or
between the reinforcement and an external environment; a reinforcement effect
must encompass a small deformation through a large deformation; and seismically
isolating reinforcement is required.
Claims (64)
- A reinforcing member comprising a woven body formed by a weaving process to have a high ductility and high bendability, said reinforcing member being adapted to be installed on a surface of a structure member or a boundary portion of said structure member, or inside said structure member, to reinforce said structure member, wherein said woven body has a Young's modulus equal to or less than that of said structure member, and a tensile fracture strain of 10% or more.
- The reinforcing member as defined in claim 1, wherein the Young's modulus of said woven body is in the range of 1/2 to 1/20 of that of said structure member.
- The reinforcing member as defined in claim 1, wherein the Young's modulus of said woven body is in the range of 1/5 to 1/10 of that of said structure member.
- The reinforcing member as defined in claim 1, wherein the Young's modulus of said woven body is in the range of 500 to 50000 MPa.
- The reinforcing member as defined in claim 1, wherein the Young's modulus of said woven body is in the range of 1000 to 10000 MPa.
- The reinforcing member as defined in claim 1, wherein said woven body has a thickness in the range of 0.2 to 20 mm.
- The reinforcing member as defined in claim 1, wherein said woven body has a thickness in the range of 0.5 to 15 mm.
- The reinforcing member as defined in claim 1, wherein said woven body has a thickness in the range of 1 to 10 mm.
- The reinforcing member as defined in claim 1, wherein said woven body includes yarns made of polyester.
- The reinforcing member as defined in claim 1, wherein said woven body has a bending deformation angle of 90-degree or more, and a shear deformation angle of 2-degree or more.
- The reinforcing member as defined in claim 1, which is heat-set to allow a Young's modulus in a limit state to be greater than a Young's modulus immediately before fracture.
- The reinforcing member as defined in claim 11, which has an elongation strain in the range of 0.1% to 10% in said limit state.
- A reinforcing member comprising a tape-shaped or sheet-shaped body made of a rubber-based or resin-based elastic material having a high ductility and high bendability, said reinforcing member being adapted to be installed on a surface of a structure member or a boundary portion of said structure member, or inside said structure member, to reinforce said structure member, wherein said tape-shaped or sheet-shaped body has a Young's modulus equal to or less than that of said structure member, and a tensile fracture strain of 10% or more.
- The reinforcing member as defined in claim 13, wherein the Young's modulus of said tape-shaped or sheet-shaped body is in the range of 1/2 to 1/20 of that of said structure member.
- The reinforcing member as defined in claim 13, wherein the Young's modulus of said tape-shaped or sheet-shaped body is in the range of 1/5 to 1/10 of that of said structure member.
- The reinforcing member as defined in claim 13, wherein the Young's modulus of said woven body is in the range of 500 to 50000 MPa.
- The reinforcing member as defined in claim 13, wherein the Young's modulus of said woven body is in the range of 1000 to 10000 MPa.
- The reinforcing member as defined in claim 13, wherein said tape-shaped or sheet-shaped body has a thickness in the range of 0.2 to 20 mm.
- The reinforcing member as defined in claim 13, wherein said tape-shaped or sheet-shaped body has a thickness in the range of 0.5 to 15 mm.
- The reinforcing member as defined in claim 13, wherein said tape-shaped or sheet-shaped body has a thickness in the range of 1 to 10 mm.
- The reinforcing member as defined in claim 13, wherein said tape-shaped or sheet-shaped body has a bending deformation angle of 90-degree or more, and a shear deformation angle of 2-degree or more.
- A reinforced structure for a structural body comprising:a reinforcing member including a woven body formed by a weaving process to have a high ductility and high bendability, said woven body having a Young's modulus equal to or less than that of a structure member of said structural body, and a tensile fracture strain of 10% or more,
- The reinforced structure as defined in claim 22, wherein said reinforcing member is fixed to said structure member in such a manner that an effective constraint range of said reinforcing member covers the pre-calculated width and length of a gap to be generated in said structure member in future.
- The reinforced structure as defined in claim 22, wherein the Young's modulus of said woven body is in the range of 1/2 to 1/20 of that of said structure member.
- The reinforced structure as defined in claim 22, wherein the Young's modulus of said woven body is in the range of 1/5 to 1/10 of that of said structure member.
- The reinforced structure as defined in claim 22, wherein the Young's modulus of said woven body is in the range of 500 to 50000 MPa.
- The reinforced structure as defined in claim 1, wherein the Young's modulus of said woven body is in the range of 1000 to 10000 MPa.
- The reinforced structure as defined in claim 22, wherein said woven body has a thickness in the range of 0.2 to 20 mm.
- The reinforced structure as defined in claim 22, wherein said woven body has a thickness in the range of 0.5 to 15 mm.
- The reinforced structure as defined in claim 22, wherein said woven body has a thickness in the range of 1 to 10 mm.
- The reinforced structure as defined in claim 22, wherein said woven body includes yarns made of polyester.
- The reinforced structure as defined in claim 31, wherein said woven body has a bending deformation angle of 90-degree or more, and a shear deformation angle of 2-degree or more.
- The reinforced structure as defined in claim 22, wherein said reinforcing member is heat-set to allow a Young's modulus in a limit state to be greater than a Young's modulus immediately before fracture.
- The reinforced structure as defined in claim 22, wherein said reinforcing member has an elongation strain in the range of 0.1 % to 10% in said limit state.
- The reinforced structure as defined in claim 22, wherein said substrate is at least one selected from the group consisting of (1) concrete, (2) steel frame, (3) brick, (4) block, (5) gypsum board or plaster board, (6) wood, (7) rock, (8) earth or soil, (9) sand, (10) resin and (11) metal.
- The reinforced structure as defined in claim 22, wherein said fixation is performed by means of an adhesive.
- The reinforced structure as defined in claim 36, wherein the layer of said adhesive applied to said reinforcing member or said structure member has a thickness in the range of 5 to 90% of the thickness of said reinforcing member.
- The reinforced structure as defined in claim 36, wherein the layer of said adhesive applied to said reinforcing member or said structure member has a thickness in the range of 20 to 40% of the thickness of said reinforcing member.
- The reinforced structure as defined in claim 36, wherein said fixation is performed by placing said reinforcing member on said structure member through the layer of said adhesive and then applying a pressing force or a beating force to said reinforcing member while allowing a part of said adhesive to be infiltrated into said reinforcing member, wherein the fixed portion of said reinforcing member has a void ratio of 1.1 or more.
- The reinforced structure as defined in claim 36, wherein the bonding strength of said fixation is less than the strength of said structure member.
- The reinforced structure as defined in claim 36, wherein said adhesive is a one-component, non-solvent adhesive.
- The reinforced structure as defined in claim 36, wherein the bonding strength of said fixation is in the range of 10 to 80% of peeling/shear fracture strength in the surface of said structure member applied with said adhesive.
- The reinforced structure as defined in claim 22, wherein said fixation is performed without chamfering said structure member and adjusting the unevenness of the surface of said structure member.
- A reinforced structure for a structural body comprising:a reinforcing member including a tape-shaped or sheet-shaped body made of a rubber-based or resin-based elastic material having a high ductility and high bendability, said tape-shaped or sheet-shaped body having a Young's modulus equal to or less than that of a structure member of said structural body, and a tensile fracture strain of 10% or more,
- The reinforced structure as defined in claim 44, wherein said reinforcing member is fixed to said structure member in such a manner that an effective constraint range of said reinforcing member covers the pre-calculated width and length of a gap to be generated in said structure member in future.
- The reinforced structure as defined in claim 44, wherein the Young's modulus of said tape-shaped or sheet-shaped body is in the range of 1/2 to 1/20 of that of said structure member.
- The reinforced structure as defined in claim 46, wherein the Young's modulus of said tape-shaped or sheet-shaped body is in the range of 1/5 to 1/10 of that of said structure member.
- The reinforced structure as defined in claim 44, wherein the Young's modulus of said tape-shaped or sheet-shaped body is in the range of 500 to 50000 MPa.
- The reinforced structure as defined in claim 44, wherein the Young's modulus of said tape-shaped or sheet-shaped body is in the range of 1000 to 10000 MPa.
- The reinforced structure as defined in claim 44, wherein said tape-shaped or sheet-shaped body has a thickness in the range of 0.2 to 20 mm.
- The reinforced structure as defined in claim 44, wherein said tape-shaped or sheet-shaped body has a thickness in the range of 0.5 to 15 mm.
- The reinforced structure as defined in claim 44, wherein said tape-shaped or sheet-shaped body has a thickness in the range of 1 to 10 mm.
- The reinforced structure as defined in claim 44, wherein said tape-shaped or sheet-shaped body has a bending deformation angle of 90-degree or more, and a shear deformation angle of 2-degree or more.
- The reinforced structure as defined in claim 44, wherein said substrate is at least one selected from the group consisting of (1) concrete, (2) steel frame, (3) brick, (4) block, (5) gypsum board or plaster board, (6) wood, (7) rock, (8) earth or soil, (9) sand, (10) resin and (11) metal.
- The reinforced structure as defined in claim 44, wherein said fixation is performed by means of an adhesive.
- The reinforced structure as defined in claim 44, wherein the layer of said adhesive applied to said reinforcing member or said structure member has a thickness in the range of 5 to 90% of the thickness of said reinforcing member.
- The reinforced structure as defined in claim 44, wherein the layer of said adhesive applied to said reinforcing member or said structure member has a thickness in the range of 20 to 40% of the thickness of said reinforcing member.
- The reinforced structure as defined in claim 44, wherein said fixation is performed by placing said reinforcing member on said structure member through the layer of said adhesive and then applying a pressing force or a beating force to said reinforcing member while allowing a part of said adhesive to be infiltrated into said reinforcing member, wherein the fixed portion of said reinforcing member has a void ratio of 1.4 or more.
- The reinforced structure as defined in claim 44, wherein the bonding strength of said fixation is less than the strength of said structure member.
- The reinforced structure as defined in claim 44, wherein said adhesive is a one-component, non-solvent adhesive.
- The reinforced structure as defined in claim 44, wherein the bonding strength of said fixation is in the range of 10 to 80% of peeling/shear fracture strength in the surface of said structure member applied with said adhesive.
- The reinforced structure as defined in claim 44, wherein said fixation is performed without chamfering said structure member and adjusting the unevenness of the surface of said structure member.
- A method of designing a reinforcing member which includes a woven body formed by a weaving process to have a high ductility and high bendability, said reinforcing member being adapted to be installed on a surface of a structure member or a boundary portion of said structure member, or inside said structure member, to reinforce said structure member, wherein said woven body has a Young's modulus equal to or less than that of said structure member, and a tensile fracture strain of 10% or more, said method comprising determining the thickness of said reinforcing member according to a calculation based on an apparent yield stress of said reinforcing member.
- A method of designing a reinforcing member which includes a tape-shaped or sheet-shaped body made of a rubber-based or resin-based elastic material having a high ductility and high bendability, said reinforcing member being adapted to be installed on a surface of a structure member or a boundary portion of said structure member, or inside said structure member, to reinforce said structure member, wherein said tape-shaped or sheet-shaped body has a Young's modulus equal to or less than that of said structure member, and a tensile fracture strain of 10% or more, said method comprising determining the thickness of said reinforcing member according to a calculation based on an apparent yield stress of said reinforcing member.
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
WOPCT/JP01/08287 | 2001-09-25 | ||
PCT/JP2001/008287 WO2003027416A1 (en) | 2001-09-25 | 2001-09-25 | Structure reinforcing construction, reinforcing material, earthquake isolation device, and reinforcing method |
WOPCT/JP02/02167 | 2002-03-08 | ||
PCT/JP2002/002167 WO2003027414A1 (en) | 2001-09-25 | 2002-03-08 | Construction and method for reinforcing structure, construction and method for base isolation, and reinforcement material |
PCT/JP2002/009838 WO2003027417A1 (en) | 2001-09-25 | 2002-09-25 | Reinforcement material and reinforcement structure of structure and method of designing reinforcement material |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1437459A1 true EP1437459A1 (en) | 2004-07-14 |
EP1437459A4 EP1437459A4 (en) | 2005-07-06 |
Family
ID=11737749
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP02775228A Withdrawn EP1437459A4 (en) | 2001-09-25 | 2002-09-25 | Reinforcement material and reinforcement structure of structure and method of designing reinforcement material |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1437459A4 (en) |
JP (3) | JPWO2003027416A1 (en) |
TN (1) | TNSN04043A1 (en) |
TW (2) | TW521113B (en) |
WO (2) | WO2003027416A1 (en) |
Cited By (2)
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ITRM20090380A1 (en) * | 2009-07-17 | 2011-01-18 | Giovanni Cenci | METHOD FOR THE REALIZATION OF AN ANTI-SEISMIC BUILDING WITH SUPPORTING STRUCTURE IN FIBRORINFORCED WOOD AND WITH SEISMIC INSULATORS. |
ITBO20120564A1 (en) * | 2012-10-16 | 2014-04-17 | Anton Massimo Galluccio | METHOD AND EQUIPMENT FOR THE REINFORCEMENT OF BUILDING STRUCTURES |
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JP4639380B2 (en) * | 2005-06-22 | 2011-02-23 | 学校法人東京理科大学 | Reinforcement method for columns with sleeve walls |
JP2008008142A (en) * | 2007-07-27 | 2008-01-17 | Ohbayashi Corp | Concrete member reinforcing structure and reinforcing method |
CN103717939B (en) * | 2011-07-28 | 2015-09-23 | 株式会社普利司通 | The manufacture method of the manufacture method of the plug composition in the plug composition in base isolation structure, base isolation structure plug, base isolation structure, base isolation structure and base isolation structure plug |
CN108979196A (en) * | 2018-08-27 | 2018-12-11 | 西安建筑科技大学 | Utilize the ruggedized construction with fill plate prevention steel-frame structure continuous collapse in R-joining |
KR102030966B1 (en) * | 2019-04-24 | 2019-10-10 | 석용희 | Member for improving adhesive strength and method for manufacturing molded article using the same |
KR102440309B1 (en) * | 2021-11-19 | 2022-09-05 | 이지안 | Seismic retrofit frame structure |
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ITBO20120564A1 (en) * | 2012-10-16 | 2014-04-17 | Anton Massimo Galluccio | METHOD AND EQUIPMENT FOR THE REINFORCEMENT OF BUILDING STRUCTURES |
Also Published As
Publication number | Publication date |
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TW521113B (en) | 2003-02-21 |
EP1437459A4 (en) | 2005-07-06 |
JPWO2003027414A1 (en) | 2005-01-06 |
WO2003027416A1 (en) | 2003-04-03 |
JPWO2003027417A1 (en) | 2005-01-06 |
TWI268980B (en) | 2006-12-21 |
TNSN04043A1 (en) | 2006-06-01 |
JPWO2003027416A1 (en) | 2005-01-06 |
WO2003027414A1 (en) | 2003-04-03 |
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