CA1243501A - Steel materials for use with prestressed concrete - Google Patents
Steel materials for use with prestressed concreteInfo
- Publication number
- CA1243501A CA1243501A CA000470178A CA470178A CA1243501A CA 1243501 A CA1243501 A CA 1243501A CA 000470178 A CA000470178 A CA 000470178A CA 470178 A CA470178 A CA 470178A CA 1243501 A CA1243501 A CA 1243501A
- Authority
- CA
- Canada
- Prior art keywords
- steel
- heat
- synthetic resin
- tube
- resin tube
- Prior art date
- 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.)
- Expired
Links
Classifications
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B1/00—Constructional features of ropes or cables
- D07B1/16—Ropes or cables with an enveloping sheathing or inlays of rubber or plastics
- D07B1/162—Ropes or cables with an enveloping sheathing or inlays of rubber or plastics characterised by a plastic or rubber enveloping sheathing
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/08—Members specially adapted to be used in prestressed constructions
-
- D—TEXTILES; PAPER
- D07—ROPES; CABLES OTHER THAN ELECTRIC
- D07B—ROPES OR CABLES IN GENERAL
- D07B2501/00—Application field
- D07B2501/20—Application field related to ropes or cables
- D07B2501/2015—Construction industries
- D07B2501/2023—Concrete enforcements
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- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Reinforcement Elements For Buildings (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Steel materials for use with concrete that is prestressed by posttensioning are disclosed. In accordance with one embodiment of the invention, a steel member is sheathed with a heat-shrinkable synthetic resin tube. A
heat-fusible synthetic resin adhesive may be coated or placed on the inner surface of the heat shrinkable synthetic resin tube or on the outer surface of the steel member such that when heat is applied to cause the resin tube to shrink, the resin adhesive melts to provide firm adhesion between the steel member and the resin tube. In another embodiment, the steel member is sheathed with a foamed synthetic resin tube. Both embodiments are further applicable to the case of a stranded steel member, in which case it is preferred that the spiral grooves of the stranded member be filled with a resin before coating with an adhesive or sheathing with an external tube.
Steel materials for use with concrete that is prestressed by posttensioning are disclosed. In accordance with one embodiment of the invention, a steel member is sheathed with a heat-shrinkable synthetic resin tube. A
heat-fusible synthetic resin adhesive may be coated or placed on the inner surface of the heat shrinkable synthetic resin tube or on the outer surface of the steel member such that when heat is applied to cause the resin tube to shrink, the resin adhesive melts to provide firm adhesion between the steel member and the resin tube. In another embodiment, the steel member is sheathed with a foamed synthetic resin tube. Both embodiments are further applicable to the case of a stranded steel member, in which case it is preferred that the spiral grooves of the stranded member be filled with a resin before coating with an adhesive or sheathing with an external tube.
Description
35~ 1 STEEL MATERIALS FOR USE WITH PRESTRESSE~ CONCRETE
The present invention relates to steel materials for use with concrete that is prestressed by posttensioning.
Concrete has a relatively low tensile strength.
In order to overcome this disadvantage, prestress~d concrete has been developed. By means of high strength steel wires, bars or strands, a concrete member is precompressed. When the structure receives a load, the compression is relieved on that portion which would normally be in tension.
There are two general methods of prestressing, namely, pretensioning and posttensioning. The present invention relates to steel materials for use with concrete of the type that is prestressed by posttensioning.
Structural designs used to prevent direct contact between steel materials and the surrounding prestressed concrete are illustrated in Figs 1 and 2.
The design shown in Fig. 1 can be used whether the steel material is in the form of a wire, bar or strand. A steel member 1 having a grease coating 2 is sheathed with a PE
(polyethylene) tube 3. When the steel member 1 with the ~s~d~
3~
The present invention relates to steel materials for use with concrete that is prestressed by posttensioning.
Concrete has a relatively low tensile strength.
In order to overcome this disadvantage, prestress~d concrete has been developed. By means of high strength steel wires, bars or strands, a concrete member is precompressed. When the structure receives a load, the compression is relieved on that portion which would normally be in tension.
There are two general methods of prestressing, namely, pretensioning and posttensioning. The present invention relates to steel materials for use with concrete of the type that is prestressed by posttensioning.
Structural designs used to prevent direct contact between steel materials and the surrounding prestressed concrete are illustrated in Figs 1 and 2.
The design shown in Fig. 1 can be used whether the steel material is in the form of a wire, bar or strand. A steel member 1 having a grease coating 2 is sheathed with a PE
(polyethylene) tube 3. When the steel member 1 with the ~s~d~
3~
2 --1 PE tube 3 is placed within a concrete section 3, the lubricating effect of the intermediate grease coating 2 reduces the coefficient of friction between the steel member and concrete to as low as between 0.002 and 0.005 m~lO Because of this low coefficient of friction, the design in Fig. 1 provides great ease in posttensioning a long steel cable in concrete. However,- if the steel material is of short length, the need for preventing grease leakage from either end of the PE tube presents treat difficulty in fabricatiny and handling the steel material. Furthermore, steel members having screws or heads at both ends are difficult to produce in a continuous fashion.
The steel member 1 shown in Fig. 2, which is encapsulated in asphalt 5, has a slightly greater coefficient ox friction than the structure shown in Fig.
1. This design is extensively used with relatively short steel materials since it is simplP in construction, is leak-free, and provides ease in unbonding the steel material from the concrete, even if the steel member has screws or heads at end portions.
One problem with the design in Fig. 2 is that the presence of the asphalt (or, alternatively, a paint) may adversely affect the working environment due to the 1 inclusion therein of a volatile organic solvent. Moreover, the floor may he fouled by the splashing of the asphalt or paint. As another probl'em, great difficulty is involved in handling the' coated steel material during drying or positioning ~lithin a framework, and separation of the asphalt coating can easily occur unless utmost care is taken in ensuring the deslred coating thickness.
SUMMP~RY OF THE INVENTION
Accordingly t a-primary obj'ect of the present invention is to provide a steel material for use with prestressed concrete that is free from the problems associated with'the prior art techniques. s These and other objects of the present invention are'achieved by sheathing a steel material for prestressed concrete with'a heat-shrinkable synthetic resin tube or a roamed synthetic resin tube.
BRIEF: DESCRIPTION OF THE DRAWINGS
Figs. 1 and 2 show schematically conventional designs of steel materials for concrete prestressed by posttensioning;
Fig 3 lS a schematic presentation of a steel material of the present invention for use with prestressed concrete; and Fig. 4 shows a cross section of a steel strand sheathed with a resin tube according to the present invention.
~435 1 Fig. 5 shows measuring apparatus used to determine the co-efficient of friction as set out in tables 2 and 5 attached to steel material of the present invention for use with pre-stressed concrete.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the present invention will be described in detail with reference to Fiys. 3 and 4, in which -reference numeral indicates a steel number tl) and reference numeral 6 (7) a heat-shrinkable synthetic resin tube (roamed synthe-tic resin tube).
embodiment 1 According to this embodiment, the steel member is sheathéd with a heat--shrinkabIe synthetic resin tube.
The steel material need not be bonded to the heat-shrinkable synthetic resin tube with an adhesive material.
If improved rust-preventiny and anti-corrosion effects are desired, the steel member and the resin tube may be bonded by an adhesive material. If the steeI member is a bar, a heat-fusibLe synthetic resin adhesive is coated or placed on the inner surface of the resin tube or the outer surface of the steel bar, and, after the resin tube is slipped over the steel bar, heat is applied to cause the resin tube to shrink as the resin adhesive melts to provide firm adhesion between the steel bar and the resin tube. In order for the resin adhesive to melt while the resin tube only shrinks ~35~
1 when they are heated, the melting point of the resin adhesive must be lower than that of the resin tube. It has been found by the present inven-tors that this method is the simplest and best way to ensure firm bonding between the steel bar an(l the synthetic resin tube.
The steel material for prestressed concrete according to the this embodiment is illustrated in Fig. 3, wherein reference numeral 1 refers to the steeI member and 6 represents the heat-shrinkable synthetic resin tube coated on the surface of the steel member. In one pre-ferred example, the steel member 1 is inserted into a pre-fabricated heat~shrinkable synthetic resin tube, which is then heated by hot air, steam Gr with an IR (infrared) heater to shrink and tightly fit it onto the surface o-E the steel member.
The fall thickness of the heat-shrinkabIe synthetic resin tube must be at least 300 microns in order to isolate the steel member 1 and the surrounding concrete layer sufficiently to provide good slippage between the two components. The wall thickness to of the synthetic resin tube after heat shrinking can be approximated by the following equation:
t = (1/2) (((D + 2tl) - Dl + Do ) 2 - Do3~
where t: wall thickness (mm) after heat shrinking Do outside diameter (mm) of steel bar Dl: inside diameter (mm) of the tube before heat shrinking l wall thickness (mm) before heat shrlnking.
, . I ,,
The steel member 1 shown in Fig. 2, which is encapsulated in asphalt 5, has a slightly greater coefficient ox friction than the structure shown in Fig.
1. This design is extensively used with relatively short steel materials since it is simplP in construction, is leak-free, and provides ease in unbonding the steel material from the concrete, even if the steel member has screws or heads at end portions.
One problem with the design in Fig. 2 is that the presence of the asphalt (or, alternatively, a paint) may adversely affect the working environment due to the 1 inclusion therein of a volatile organic solvent. Moreover, the floor may he fouled by the splashing of the asphalt or paint. As another probl'em, great difficulty is involved in handling the' coated steel material during drying or positioning ~lithin a framework, and separation of the asphalt coating can easily occur unless utmost care is taken in ensuring the deslred coating thickness.
SUMMP~RY OF THE INVENTION
Accordingly t a-primary obj'ect of the present invention is to provide a steel material for use with prestressed concrete that is free from the problems associated with'the prior art techniques. s These and other objects of the present invention are'achieved by sheathing a steel material for prestressed concrete with'a heat-shrinkable synthetic resin tube or a roamed synthetic resin tube.
BRIEF: DESCRIPTION OF THE DRAWINGS
Figs. 1 and 2 show schematically conventional designs of steel materials for concrete prestressed by posttensioning;
Fig 3 lS a schematic presentation of a steel material of the present invention for use with prestressed concrete; and Fig. 4 shows a cross section of a steel strand sheathed with a resin tube according to the present invention.
~435 1 Fig. 5 shows measuring apparatus used to determine the co-efficient of friction as set out in tables 2 and 5 attached to steel material of the present invention for use with pre-stressed concrete.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the present invention will be described in detail with reference to Fiys. 3 and 4, in which -reference numeral indicates a steel number tl) and reference numeral 6 (7) a heat-shrinkable synthetic resin tube (roamed synthe-tic resin tube).
embodiment 1 According to this embodiment, the steel member is sheathéd with a heat--shrinkabIe synthetic resin tube.
The steel material need not be bonded to the heat-shrinkable synthetic resin tube with an adhesive material.
If improved rust-preventiny and anti-corrosion effects are desired, the steel member and the resin tube may be bonded by an adhesive material. If the steeI member is a bar, a heat-fusibLe synthetic resin adhesive is coated or placed on the inner surface of the resin tube or the outer surface of the steel bar, and, after the resin tube is slipped over the steel bar, heat is applied to cause the resin tube to shrink as the resin adhesive melts to provide firm adhesion between the steel bar and the resin tube. In order for the resin adhesive to melt while the resin tube only shrinks ~35~
1 when they are heated, the melting point of the resin adhesive must be lower than that of the resin tube. It has been found by the present inven-tors that this method is the simplest and best way to ensure firm bonding between the steel bar an(l the synthetic resin tube.
The steel material for prestressed concrete according to the this embodiment is illustrated in Fig. 3, wherein reference numeral 1 refers to the steeI member and 6 represents the heat-shrinkable synthetic resin tube coated on the surface of the steel member. In one pre-ferred example, the steel member 1 is inserted into a pre-fabricated heat~shrinkable synthetic resin tube, which is then heated by hot air, steam Gr with an IR (infrared) heater to shrink and tightly fit it onto the surface o-E the steel member.
The fall thickness of the heat-shrinkabIe synthetic resin tube must be at least 300 microns in order to isolate the steel member 1 and the surrounding concrete layer sufficiently to provide good slippage between the two components. The wall thickness to of the synthetic resin tube after heat shrinking can be approximated by the following equation:
t = (1/2) (((D + 2tl) - Dl + Do ) 2 - Do3~
where t: wall thickness (mm) after heat shrinking Do outside diameter (mm) of steel bar Dl: inside diameter (mm) of the tube before heat shrinking l wall thickness (mm) before heat shrlnking.
, . I ,,
3~
l If a steel bar of Do = 17 on is inserted into a resin tube having an inside diameter of 20 mm and a wall thickness of 0.3 mm and if the tube is heat-shrunk to prov'ide intimate'contact with the steeI bar, the tube around the steeI bar will have a wall thickness as large as about 0.35 mm. A heat-shrinkable polyolefin tube has a heat shrinkage of about 35%. Thus, the'inside diameter of he tube can be sel'ected from the'range'of l.l to 1.5 times 1:he outside'diameter of the steeI bar. This fairly large :inside diameter of the polyolefin tube permits considerable ease in inserting the steel bar through the tube. Further-nore, by properly seIecting the inside diameter and wall 1:hickness of the heat-shrinkable syntheti,c~"resin tube to be used with'a steel bar having a specific outside diameter 9 the desired wall thickness of the tube will be provided around the steeI bar after heat shrinkage.
Samples of steel materials for use'with prestressed concrete that included steel members coated with a heat-shrinkable synthetic resin tube were fabricated and subjected to various tests to determine their properties.
The results are shown in Tables 1 to 3, The method of measuring the frictional coefficient will be described with reference to Fig. 5.
First, the sample 24 as obtained from the above procedure was placed in concrete 23 and thereafter the concrete was solidified. toad cells 21 were provided at 3S~3~
1 both end portions o~'the sample member of wire 24 which' were'expose~ from bbth sides of the concret'e 23'and then tension was applied to the sample member 24 by a jack 22 provided at one end of the sample member 24 as shown in Fig. 5, At this time, a load applied to one end of the sample member by using the jack 22 and a load transmitted through the sample member applied to the other end of the sample member, i.e., the fixed side of the' sample member, were simultaneously detec-ted through both of the load cells 21 by a loadmeasuring detector 25.
Herel if Pi is defined as the'load at the~.applicati~n side of the tension using the jack and Po is defined as the load applied to the fixed side of the sample member 24, the friction between the sample membe'r and the concrete is obtained by subtracting Po from Pi and the frictional coefficient at unit length'of the sample member is obtained from the following equation:
, ;~ = (Pi - Po) /Po.~ = (Pi/Po - l 3L~43S~?l 1 Table 1 Basic properties of SamPles Dimensions of Bar having an outside diameter of steel member: 17 mm and a length of 2,830 mm . 5 Resin tube: High-density polyethylene tube that was rendered heat-shrinkable by cross-linking under exposure to electron beam Density: 0.95 g/cm2 Tensile strength: 1.0 kyJmm2 Elongation: 300%
Heat resistance: 350C (1 min.) Saltwater resistance: OK
Alkali resistance: OK
Acid resistance: ~10% HC1) OK
tl0% H2SO4) OK
35~
1 Table 2 Unbonding (Frictional) Properties Load (Kgf) Frictional Frictional Sample Tensioned Fixed loss (Kgf) coefficient No._ Side(Po) A (Mel) Remarks 1 19O490 19~110 380 0~00817 Length of concrete 2 19.540 19.135 405 0.00869 section:
Q=2,435 mm 3 19~530 19.190 340 0.00728
l If a steel bar of Do = 17 on is inserted into a resin tube having an inside diameter of 20 mm and a wall thickness of 0.3 mm and if the tube is heat-shrunk to prov'ide intimate'contact with the steeI bar, the tube around the steeI bar will have a wall thickness as large as about 0.35 mm. A heat-shrinkable polyolefin tube has a heat shrinkage of about 35%. Thus, the'inside diameter of he tube can be sel'ected from the'range'of l.l to 1.5 times 1:he outside'diameter of the steeI bar. This fairly large :inside diameter of the polyolefin tube permits considerable ease in inserting the steel bar through the tube. Further-nore, by properly seIecting the inside diameter and wall 1:hickness of the heat-shrinkable syntheti,c~"resin tube to be used with'a steel bar having a specific outside diameter 9 the desired wall thickness of the tube will be provided around the steeI bar after heat shrinkage.
Samples of steel materials for use'with prestressed concrete that included steel members coated with a heat-shrinkable synthetic resin tube were fabricated and subjected to various tests to determine their properties.
The results are shown in Tables 1 to 3, The method of measuring the frictional coefficient will be described with reference to Fig. 5.
First, the sample 24 as obtained from the above procedure was placed in concrete 23 and thereafter the concrete was solidified. toad cells 21 were provided at 3S~3~
1 both end portions o~'the sample member of wire 24 which' were'expose~ from bbth sides of the concret'e 23'and then tension was applied to the sample member 24 by a jack 22 provided at one end of the sample member 24 as shown in Fig. 5, At this time, a load applied to one end of the sample member by using the jack 22 and a load transmitted through the sample member applied to the other end of the sample member, i.e., the fixed side of the' sample member, were simultaneously detec-ted through both of the load cells 21 by a loadmeasuring detector 25.
Herel if Pi is defined as the'load at the~.applicati~n side of the tension using the jack and Po is defined as the load applied to the fixed side of the sample member 24, the friction between the sample membe'r and the concrete is obtained by subtracting Po from Pi and the frictional coefficient at unit length'of the sample member is obtained from the following equation:
, ;~ = (Pi - Po) /Po.~ = (Pi/Po - l 3L~43S~?l 1 Table 1 Basic properties of SamPles Dimensions of Bar having an outside diameter of steel member: 17 mm and a length of 2,830 mm . 5 Resin tube: High-density polyethylene tube that was rendered heat-shrinkable by cross-linking under exposure to electron beam Density: 0.95 g/cm2 Tensile strength: 1.0 kyJmm2 Elongation: 300%
Heat resistance: 350C (1 min.) Saltwater resistance: OK
Alkali resistance: OK
Acid resistance: ~10% HC1) OK
tl0% H2SO4) OK
35~
1 Table 2 Unbonding (Frictional) Properties Load (Kgf) Frictional Frictional Sample Tensioned Fixed loss (Kgf) coefficient No._ Side(Po) A (Mel) Remarks 1 19O490 19~110 380 0~00817 Length of concrete 2 19.540 19.135 405 0.00869 section:
Q=2,435 mm 3 19~530 19.190 340 0.00728
4 19.480 19.105 375 0.008~6 Sample S l9.S10 19.015 495 0.01059 tempera-ture:
.6 19O500 19.185 315 0.00674 T=25C
7 19.520 19.065 455 0.00980 Frictional 8 19~500 18.970 530 0.01147 coeffi-cient:
9 19.510 19.080 430 0.00926 =(Pi 1) 15 10 19.~70 19.110 360 o.oa774 35~
g 1 Table 3 Test Conditions Results 1. Continuous JIS Z 2371 No rust or blister saltwater (5~ aq. NaCl, 35C) formed on the sample spray test surface (2,000 hrs) No rust on the internal steel bar.
2. Saltwater Immersed in 3% aq~ No rust or blister immerion test NaCl at 25C formed on the sample (2,000 hrs) surface.
No rust on the internal steel bar.
3. Alkali Immersed in 3% aq. Mo rust or blister resistance NaCl at 25C that formed on the sample test was adjested to surfact.
(2,000 hrs) pH 11 with KOH
No rust on the internal steel bar.
~2435~
1 Embodiment 2 According to this embodiment, the steel member is sheathed by a foamed synthetic resin tube 7 in Fig 3.
Various methods may be used to cover the steel member 1 with the resin tube In one method, a synthetic resin powder containing a blowing agent is applied to provida a foamed coating on the surface of a preheated steel member by a fluidized dip coating or electrostatic coating technique Alternatively, a film oF synthetic resin containing a blowing agent is formed on the surface of the steel member 1, which is then passed through a heating chamber to expand the resin film into a foam. If desired, a preliminarily formed synthetic resin foam tube 6 may be slipped over the steel member lo The resln tube 6 may or may to be bonded to the steel member 1.
In order to isolate the steel material sufficiently from concrete to facilitate the subsequent posttensioning, the foamed synthetic resin tube 6 must have a wall thickness of at least 300 microns.
Furthermore, in order to reduce the frictional resistance and therefore the slippage between the steel member 1 and the concrete, the resin tube 6 preferably has a wall thickness of at least 500 microns.
Steel bars, one example oE a steel member 2435~
1 according to the present invention, were sheathed with a foamed polyethylene tube. The tube was prepared from a blowing agent loaded polyethylene powder that was applied to preheated steel bars using a fluidized dip coating technique. The properties of these samples were as sown in Tables 4 and 5:
~'9L3~
1 Tabl _ Basic Properties of Steel Bars -L
Bar dimensions: 17 mm~ X 2,830 mm Polyethylene tube: prepared from medium-density PE powder (density. 0.925 g/cm3, m.p. 120C) containing 1.0~
heat-decomposable blowing agent Wall thickness of 1~3 - 1.5 mm polyethylene tube:
Occluded cells: Open cells of a size of 0.3 - 0.5 mm distributed uniformity in a thickness ox 3 - 4 microns ~2~L35~
1 Table 5 Unbondinq_(Fri.ctional) Properties Load (Kgf) Frictional Frictional Sample Tensioned Fixed loss (Kgf) coefficient No. side (Pi) Side(Po) (m~1) Remarks 1 19.510 19.140 370 0.0079 Length of concrete 2 19.540 19.200 340 0.0073 section:
~=2,435 mm 3 19.500 19.010 490 0~0106 4 19.480 19.040 440 0.0095 Sample 19.510 19O115 395 0.0085 tempera-. ture:
.6 19.530 19.170 360 0.0077 T=25C
7 19.500 19.040. 455 0.009~
Frictional S 19.510 18.965 545 0.0118 coeffi-cient:
9 19.500 19.220 280 0.0060 ~=(Ppi 19.490 19.125 365 0.0078 ~LZ~3~
-- _4 1 Table 6 Resin coat Thickness Surface Same (microns) features Result Barax 300 - 500 unscratched No rust ormed (unbonded) even after 2,000 hrs Barax 300 - 500 scratched Severe rust formed (unbonded) around scratches . after 200 hrs Foamed 300 - 500 unscrachted No rust formed polyethylene even after 2,000 hrs coating Foamed 300 - 500 scratched Rust formed only polyethylene at scratches coating ater 500 hrs . . .
35~i~
1 The present invention is also applicable to a steel strand composed of a plurality of twisted steel wires as shown in Fig. 4. The resulting steel strand has spiral grooves as indicated by A and B in Fig. 4. Not onlv do these grooves render the posttensioning of the strand difficult, but they also increase the frictional resistance on the stressed concrete. In order to avoid these problems, the grooves are filled with a resin. Such filling with a resin may be accomplished by extrusion or other suitable techniques. Subsequently, the thus-treated steel strand is sheathed with the foamed synthetic resin -tube as above.
According to the present invention, a steel material for use with prestressed concrete can be easily manufacturedO The resulting steel material is easy to handle during transportation and installation.
.6 19O500 19.185 315 0.00674 T=25C
7 19.520 19.065 455 0.00980 Frictional 8 19~500 18.970 530 0.01147 coeffi-cient:
9 19.510 19.080 430 0.00926 =(Pi 1) 15 10 19.~70 19.110 360 o.oa774 35~
g 1 Table 3 Test Conditions Results 1. Continuous JIS Z 2371 No rust or blister saltwater (5~ aq. NaCl, 35C) formed on the sample spray test surface (2,000 hrs) No rust on the internal steel bar.
2. Saltwater Immersed in 3% aq~ No rust or blister immerion test NaCl at 25C formed on the sample (2,000 hrs) surface.
No rust on the internal steel bar.
3. Alkali Immersed in 3% aq. Mo rust or blister resistance NaCl at 25C that formed on the sample test was adjested to surfact.
(2,000 hrs) pH 11 with KOH
No rust on the internal steel bar.
~2435~
1 Embodiment 2 According to this embodiment, the steel member is sheathed by a foamed synthetic resin tube 7 in Fig 3.
Various methods may be used to cover the steel member 1 with the resin tube In one method, a synthetic resin powder containing a blowing agent is applied to provida a foamed coating on the surface of a preheated steel member by a fluidized dip coating or electrostatic coating technique Alternatively, a film oF synthetic resin containing a blowing agent is formed on the surface of the steel member 1, which is then passed through a heating chamber to expand the resin film into a foam. If desired, a preliminarily formed synthetic resin foam tube 6 may be slipped over the steel member lo The resln tube 6 may or may to be bonded to the steel member 1.
In order to isolate the steel material sufficiently from concrete to facilitate the subsequent posttensioning, the foamed synthetic resin tube 6 must have a wall thickness of at least 300 microns.
Furthermore, in order to reduce the frictional resistance and therefore the slippage between the steel member 1 and the concrete, the resin tube 6 preferably has a wall thickness of at least 500 microns.
Steel bars, one example oE a steel member 2435~
1 according to the present invention, were sheathed with a foamed polyethylene tube. The tube was prepared from a blowing agent loaded polyethylene powder that was applied to preheated steel bars using a fluidized dip coating technique. The properties of these samples were as sown in Tables 4 and 5:
~'9L3~
1 Tabl _ Basic Properties of Steel Bars -L
Bar dimensions: 17 mm~ X 2,830 mm Polyethylene tube: prepared from medium-density PE powder (density. 0.925 g/cm3, m.p. 120C) containing 1.0~
heat-decomposable blowing agent Wall thickness of 1~3 - 1.5 mm polyethylene tube:
Occluded cells: Open cells of a size of 0.3 - 0.5 mm distributed uniformity in a thickness ox 3 - 4 microns ~2~L35~
1 Table 5 Unbondinq_(Fri.ctional) Properties Load (Kgf) Frictional Frictional Sample Tensioned Fixed loss (Kgf) coefficient No. side (Pi) Side(Po) (m~1) Remarks 1 19.510 19.140 370 0.0079 Length of concrete 2 19.540 19.200 340 0.0073 section:
~=2,435 mm 3 19.500 19.010 490 0~0106 4 19.480 19.040 440 0.0095 Sample 19.510 19O115 395 0.0085 tempera-. ture:
.6 19.530 19.170 360 0.0077 T=25C
7 19.500 19.040. 455 0.009~
Frictional S 19.510 18.965 545 0.0118 coeffi-cient:
9 19.500 19.220 280 0.0060 ~=(Ppi 19.490 19.125 365 0.0078 ~LZ~3~
-- _4 1 Table 6 Resin coat Thickness Surface Same (microns) features Result Barax 300 - 500 unscratched No rust ormed (unbonded) even after 2,000 hrs Barax 300 - 500 scratched Severe rust formed (unbonded) around scratches . after 200 hrs Foamed 300 - 500 unscrachted No rust formed polyethylene even after 2,000 hrs coating Foamed 300 - 500 scratched Rust formed only polyethylene at scratches coating ater 500 hrs . . .
35~i~
1 The present invention is also applicable to a steel strand composed of a plurality of twisted steel wires as shown in Fig. 4. The resulting steel strand has spiral grooves as indicated by A and B in Fig. 4. Not onlv do these grooves render the posttensioning of the strand difficult, but they also increase the frictional resistance on the stressed concrete. In order to avoid these problems, the grooves are filled with a resin. Such filling with a resin may be accomplished by extrusion or other suitable techniques. Subsequently, the thus-treated steel strand is sheathed with the foamed synthetic resin -tube as above.
According to the present invention, a steel material for use with prestressed concrete can be easily manufacturedO The resulting steel material is easy to handle during transportation and installation.
Claims (17)
1. An elongated prestressing steel material embedded in prestressed concrete, comprising:
an elongated ungreased steel member, and a foamed synthetic resin tube sheathing bonded to said steel member and not bonded to said concrete.
an elongated ungreased steel member, and a foamed synthetic resin tube sheathing bonded to said steel member and not bonded to said concrete.
2. The prestressing steel material of claim 1, wherein a wall thickness of said tube is at least 300 microns.
3. The prestressing steel material of claim 1, wherein a wall thickness of said tube is at least 500 microns.
4. The prestressing steel material of claim 1, wherein said synthetic resin is a foamed polyethylene tube.
5. The prestressing steel material of claim 1, wherein said synthetic resin tube is formed by applying a synthetic resin powder containing a blowing agent to a surface of a preheated steel member.
6. The prestressing steel material of claim 1, wherein said synthetic resin tube is formed by applying a film of synthetic resin containing a blowing agent to a surface of
6. The prestressing steel material of claim 1, wherein said synthetic resin tube is formed by applying a film of synthetic resin containing a blowing agent to a surface of
Claim 6 continued....
said steel member and then heating said steel member to expand said resin into a foam.
said steel member and then heating said steel member to expand said resin into a foam.
7. An elongated ungreased prestressing steel material embedded in prestressed concrete, comprising:
a steel strand having a plurality of twisted steel wires, said steel strand having a plurality of spiral grooves formed therein;
a resin filling said grooves; and a foamed synthetic resin tube sheathing bonded to said strand and not bonded to said concrete.
a steel strand having a plurality of twisted steel wires, said steel strand having a plurality of spiral grooves formed therein;
a resin filling said grooves; and a foamed synthetic resin tube sheathing bonded to said strand and not bonded to said concrete.
8. A steel material for use with prestressed concrete, comprising a steel strand comprising:
a plurality of twisted steel wires, said steel strand having a plurality of spiral grooves formed therein;
a resin filling said grooves; and a foamed synthetic resin tube sheathing said strand and said resin filling said grooves.
9. An elongated prestressing steel material embedded in prestressed concrete, wherein said prestressing steel material comprises:
a plurality of twisted steel wires, said steel strand having a plurality of spiral grooves formed therein;
a resin filling said grooves; and a foamed synthetic resin tube sheathing said strand and said resin filling said grooves.
9. An elongated prestressing steel material embedded in prestressed concrete, wherein said prestressing steel material comprises:
Claim 9 continued....
a steel member and a heat-shrinkable synthetic resin tube surrounding the outer surfaces of said steel member, and in which the prestressing steel material is subjected to posttensioning in an unbounded state wherein the prestressing steel material is not bonded to and is free to move relative to the concrete, and wherein the steel member is bonded to and is not movable relative to the heat-shrinkable synthetic resin tube.
10. A prestressing steel material embedded in prestressed concrete, wherein said prestressing steel material comprises:
a steel strand comprising a plurality of steel wires twisted together, said steel strand having spiral grooves;
a resin filling said grooves; and a heat-shrinkable synthetic resin tube covering said strand and said resin and heat-shrunk around said strand to provide intimate contact between said strand and said resin tube and further comprising an adhesive material provided between the steel member and the heat-shrinkable synthetic resin tube, wherein upon application of heat, the tube shrinks as the adhesive meets to adhere the steel member and the resin tube and wherein the prestressing steel
a steel member and a heat-shrinkable synthetic resin tube surrounding the outer surfaces of said steel member, and in which the prestressing steel material is subjected to posttensioning in an unbounded state wherein the prestressing steel material is not bonded to and is free to move relative to the concrete, and wherein the steel member is bonded to and is not movable relative to the heat-shrinkable synthetic resin tube.
10. A prestressing steel material embedded in prestressed concrete, wherein said prestressing steel material comprises:
a steel strand comprising a plurality of steel wires twisted together, said steel strand having spiral grooves;
a resin filling said grooves; and a heat-shrinkable synthetic resin tube covering said strand and said resin and heat-shrunk around said strand to provide intimate contact between said strand and said resin tube and further comprising an adhesive material provided between the steel member and the heat-shrinkable synthetic resin tube, wherein upon application of heat, the tube shrinks as the adhesive meets to adhere the steel member and the resin tube and wherein the prestressing steel
Claim 10 continued....
material is free to move relative to the concrete and the steel strand is not movable relative to the heat-shrinkable synthetic resin tube.
material is free to move relative to the concrete and the steel strand is not movable relative to the heat-shrinkable synthetic resin tube.
11. An elongated prestressing steel material embedded in prestressed concrete, wherein said prestressing steel material comprises:
a steel member;
a heat-shrinkable synthetic resin tube surrounding the outer surfaces of said steel member; and an adhesive material provided between the steel member and the heat-shrinkable synthetic resin tube, wherein upon application of heat, the tube shrinks as the adhesive melts to adhere the steel member and the resin tube and wherein the prestressing steel material is in an unbonded state and is free to move with respect to the concrete and the steel member is not movable relative to the heat-shrinkable synthetic resin tube.
a steel member;
a heat-shrinkable synthetic resin tube surrounding the outer surfaces of said steel member; and an adhesive material provided between the steel member and the heat-shrinkable synthetic resin tube, wherein upon application of heat, the tube shrinks as the adhesive melts to adhere the steel member and the resin tube and wherein the prestressing steel material is in an unbonded state and is free to move with respect to the concrete and the steel member is not movable relative to the heat-shrinkable synthetic resin tube.
12. The steel material of claim 11, wherein a wall thickness of said resin tube is at least 300 microns.
13. The steel material of claim 11, wherein said resin material is a polyolefin.
14. The steel material of claim 11, wherein said resin is a high-density polyethylene.
15. A steel material for use with prestressed concrete, comprising:
a steel member;
a synthetic resin tube surrounding outer surfaces of said steel member and made of a heat-shrinkable resin;
a heat-fusible synthetic resin adhesive, said adhesive being provided between said steel member and said heat-shrinkable synthetic resin tube, said adhesive having a melting point point lower than that of the resin tube;
whereby said heat-fusible synthetic resin adhesive melts when heat is applied to the heat-shrinkable resin tube to provide firm adhesion between the heat-shrinkable tube and the steel member.
a steel member;
a synthetic resin tube surrounding outer surfaces of said steel member and made of a heat-shrinkable resin;
a heat-fusible synthetic resin adhesive, said adhesive being provided between said steel member and said heat-shrinkable synthetic resin tube, said adhesive having a melting point point lower than that of the resin tube;
whereby said heat-fusible synthetic resin adhesive melts when heat is applied to the heat-shrinkable resin tube to provide firm adhesion between the heat-shrinkable tube and the steel member.
16. A steel material for use with prestressed concrete, comprising:
a steel strand comprising a plurality of steel wires twisted together, said steel strand having spiral grooves;
a resin filling said grooves; and a heat-shrinkable synthetic resin tube covering said strand and said resin and heat-shrunk around said strand to provide intimate contact between said strand and said resin tube.
a steel strand comprising a plurality of steel wires twisted together, said steel strand having spiral grooves;
a resin filling said grooves; and a heat-shrinkable synthetic resin tube covering said strand and said resin and heat-shrunk around said strand to provide intimate contact between said strand and said resin tube.
17. The steel material of claim 16, further comprising a heat-fusible synthetic resin adhesive, said adhesive being provided between said steel strand having spiral grooves and the heat-shrinkable resin tube which covers said steel strand, said adhesive having a melting point lower than that of the resin tube, whereby said heat-fusible synthetic resin adhesive melts when heat is applied to the heat-shrinkable resin tube to provide firm adhesion between the heat-shrinkable tube and the steel member.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP194473/83 | 1983-12-16 | ||
| JP1983194474U JPS60102327U (en) | 1983-12-16 | 1983-12-16 | PC steel material |
| JP1983194473U JPS60102326U (en) | 1983-12-16 | 1983-12-16 | PC steel material |
| JP194474/83 | 1983-12-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1243501A true CA1243501A (en) | 1988-10-25 |
Family
ID=26508522
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000470178A Expired CA1243501A (en) | 1983-12-16 | 1984-12-14 | Steel materials for use with prestressed concrete |
Country Status (5)
| Country | Link |
|---|---|
| EP (2) | EP0146126B1 (en) |
| AU (2) | AU571913B2 (en) |
| CA (1) | CA1243501A (en) |
| DE (2) | DE3485807T2 (en) |
| NZ (1) | NZ210568A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104847055A (en) * | 2015-03-16 | 2015-08-19 | 山西省交通科学研究院 | Grouting-free adhesive-bonded prestressed steel bar and preparation and construction method thereof |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0198398B1 (en) * | 1985-04-08 | 1990-08-01 | Sumitomo Electric Industries Limited | Prestressing steel material |
| JPH0811791B2 (en) * | 1987-07-27 | 1996-02-07 | 神鋼鋼線工業株式会社 | Coating material for prestressed concrete tendons |
| AU625551B2 (en) * | 1990-02-08 | 1992-07-16 | Shinko Wire Company, Ltd also known as Shinko Kosen Kogyo Kabushiki Kaisha | Tendons for prestressed concrete structures and method of using and process for making such tendons |
| AUPN645295A0 (en) * | 1995-11-08 | 1995-11-30 | Armacel Pty Limited | A reinforcing bar |
| DE102014003015A1 (en) * | 2014-03-07 | 2015-09-10 | Tss Technische Sicherheits-Systeme Gmbh | Concrete guide wall and method for producing a concrete guide wall |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1559568B2 (en) * | 1965-02-11 | 1976-04-08 | Intercontinentale-Technik Gesellschaft f. Planung u. Konstruktion mbH, 8000 München | TENSIONER |
| FR2059452A1 (en) * | 1969-08-07 | 1971-06-04 | Alexandre Pierre | Protecting steel prestressing members inconcrete |
| US3646748A (en) * | 1970-03-24 | 1972-03-07 | Frederic A Lang | Tendons for prestressed concrete and process for making such tendons |
| DE2703670C2 (en) * | 1977-01-29 | 1983-11-10 | Drahtseilwerk Saar GmbH, 6654 Kirkel | Wire rope with a rope core encased in foamed plastic |
| DE2911212A1 (en) * | 1979-03-22 | 1980-10-23 | Falkner Horst | Concrete stress members compound layered sheathing - has heated inner plastics layer swelling into cavities in outer insulating layer |
-
1984
- 1984-12-14 EP EP19840115412 patent/EP0146126B1/en not_active Expired - Lifetime
- 1984-12-14 EP EP19880111961 patent/EP0298524B1/en not_active Expired - Lifetime
- 1984-12-14 DE DE19843485807 patent/DE3485807T2/en not_active Expired - Lifetime
- 1984-12-14 AU AU36677/84A patent/AU571913B2/en not_active Ceased
- 1984-12-14 CA CA000470178A patent/CA1243501A/en not_active Expired
- 1984-12-14 NZ NZ21056884A patent/NZ210568A/en unknown
- 1984-12-14 DE DE8484115412T patent/DE3485571D1/en not_active Expired - Fee Related
-
1988
- 1988-02-24 AU AU12147/88A patent/AU582321B2/en not_active Ceased
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104847055A (en) * | 2015-03-16 | 2015-08-19 | 山西省交通科学研究院 | Grouting-free adhesive-bonded prestressed steel bar and preparation and construction method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| NZ210568A (en) | 1991-01-29 |
| AU1214788A (en) | 1988-06-02 |
| DE3485571D1 (en) | 1992-04-16 |
| AU3667784A (en) | 1985-06-20 |
| AU571913B2 (en) | 1988-04-28 |
| EP0298524A3 (en) | 1989-02-01 |
| DE3485807T2 (en) | 1992-12-10 |
| EP0146126A3 (en) | 1986-12-17 |
| EP0298524A2 (en) | 1989-01-11 |
| AU582321B2 (en) | 1989-03-16 |
| EP0146126A2 (en) | 1985-06-26 |
| EP0298524B1 (en) | 1992-07-08 |
| DE3485807D1 (en) | 1992-08-13 |
| EP0146126B1 (en) | 1992-03-11 |
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| MKEX | Expiry |