NZ728649B2 - A gluelam structural member and a method of producing such a gluelam structural member - Google Patents
A gluelam structural member and a method of producing such a gluelam structural memberInfo
- Publication number
- NZ728649B2 NZ728649B2 NZ728649A NZ72864915A NZ728649B2 NZ 728649 B2 NZ728649 B2 NZ 728649B2 NZ 728649 A NZ728649 A NZ 728649A NZ 72864915 A NZ72864915 A NZ 72864915A NZ 728649 B2 NZ728649 B2 NZ 728649B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- lamellae
- structural member
- layer
- log
- wood
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 32
- 239000002023 wood Substances 0.000 claims abstract description 43
- 238000005452 bending Methods 0.000 claims abstract description 24
- 241000446313 Lamella Species 0.000 claims abstract description 17
- 229920002522 Wood fibre Polymers 0.000 claims description 16
- 239000002025 wood fiber Substances 0.000 claims description 16
- 238000005520 cutting process Methods 0.000 claims description 10
- 238000004026 adhesive bonding Methods 0.000 claims description 8
- 230000007423 decrease Effects 0.000 claims description 3
- 239000002994 raw material Substances 0.000 abstract description 9
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 239000010410 layer Substances 0.000 description 60
- 230000007547 defect Effects 0.000 description 6
- 238000001035 drying Methods 0.000 description 6
- 150000002500 ions Chemical class 0.000 description 6
- 210000001145 finger joint Anatomy 0.000 description 3
- 238000003475 lamination Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000007858 starting material Substances 0.000 description 3
- 241000826860 Trapezium Species 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 239000003292 glue Substances 0.000 description 2
- 238000005304 joining Methods 0.000 description 2
- 238000010030 laminating Methods 0.000 description 2
- 241000694515 Calidris tenuirostris Species 0.000 description 1
- 240000007182 Ochroma pyramidale Species 0.000 description 1
- 241000218657 Picea Species 0.000 description 1
- 235000008124 Picea excelsa Nutrition 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 241000894007 species Species 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27B—SAWS FOR WOOD OR SIMILAR MATERIAL; COMPONENTS OR ACCESSORIES THEREFOR
- B27B1/00—Methods for subdividing trunks or logs essentially involving sawing
- B27B1/005—Methods for subdividing trunks or logs essentially involving sawing including the step of dividing the log into sector-shaped segments
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27M—WORKING OF WOOD NOT PROVIDED FOR IN SUBCLASSES B27B - B27L; MANUFACTURE OF SPECIFIC WOODEN ARTICLES
- B27M3/00—Manufacture or reconditioning of specific semi-finished or finished articles
- B27M3/0013—Manufacture or reconditioning of specific semi-finished or finished articles of composite or compound articles
- B27M3/0026—Manufacture or reconditioning of specific semi-finished or finished articles of composite or compound articles characterised by oblong elements connected laterally
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27M—WORKING OF WOOD NOT PROVIDED FOR IN SUBCLASSES B27B - B27L; MANUFACTURE OF SPECIFIC WOODEN ARTICLES
- B27M3/00—Manufacture or reconditioning of specific semi-finished or finished articles
- B27M3/0013—Manufacture or reconditioning of specific semi-finished or finished articles of composite or compound articles
- B27M3/0026—Manufacture or reconditioning of specific semi-finished or finished articles of composite or compound articles characterised by oblong elements connected laterally
- B27M3/0053—Manufacture or reconditioning of specific semi-finished or finished articles of composite or compound articles characterised by oblong elements connected laterally using glue
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27M—WORKING OF WOOD NOT PROVIDED FOR IN SUBCLASSES B27B - B27L; MANUFACTURE OF SPECIFIC WOODEN ARTICLES
- B27M3/00—Manufacture or reconditioning of specific semi-finished or finished articles
- B27M3/0013—Manufacture or reconditioning of specific semi-finished or finished articles of composite or compound articles
- B27M3/0086—Manufacture or reconditioning of specific semi-finished or finished articles of composite or compound articles characterised by connecting using glue
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
- E04C3/12—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
- E04C3/12—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members
- E04C3/122—Laminated
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
- E04C3/12—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members
- E04C3/125—End caps therefor
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/19—Sheets or webs edge spliced or joined
- Y10T428/192—Sheets or webs coplanar
- Y10T428/195—Beveled, stepped, or skived in thickness
Abstract
structural member (10), such as a beam, a stud or a joist, is disclosed. The structural member comprises a plurality of glued-together wood lamellae (20a, 20b), each having a lamella cross section which is parallel with a cross section of the structural member (10) and a longitudinal direction which is parallel with a longitudinal direction of the structural member and with a principal grain direction of the wood lamellae (20a, 20b). In the structural member, the lamellae (20a, 20b) are formed as radial sections of a log and present cross sections which are triangular or trapezoidal and present a respective base surface (bs1) that is formed at a radially outer part of the log. The lamellae (20a, 20b) are arranged as at least two glued-together layers (L1, L2, L3) in which base surfaces (bs1) of a pair of immediately adjacent lamellae (20a, 20b) face opposite directions. The base surfaces (bs1) are perpendicular to the bending direction (B) provided by a vertical load of the structural member (10). A layer (L1) that is positioned closer, as seen in the main bending direction, to an outer face of the structural member presents a smaller number of annual rings than a layer (L2) that is positioned further away from the outer face. The structural member provides improved use of timber raw material in the manufacture of the structural member, as well as improved strength and/or reduced variation in strength between different beams. In particular, in the layer having the smaller number of annual rings, those lamellae may have a greater average annual ring radius of curvature than the lamellae of the layer that is positioned further away from the outer face. Hence, the outer layer will have higher strength. A method of forming a structural member is also disclosed. ch is parallel with a longitudinal direction of the structural member and with a principal grain direction of the wood lamellae (20a, 20b). In the structural member, the lamellae (20a, 20b) are formed as radial sections of a log and present cross sections which are triangular or trapezoidal and present a respective base surface (bs1) that is formed at a radially outer part of the log. The lamellae (20a, 20b) are arranged as at least two glued-together layers (L1, L2, L3) in which base surfaces (bs1) of a pair of immediately adjacent lamellae (20a, 20b) face opposite directions. The base surfaces (bs1) are perpendicular to the bending direction (B) provided by a vertical load of the structural member (10). A layer (L1) that is positioned closer, as seen in the main bending direction, to an outer face of the structural member presents a smaller number of annual rings than a layer (L2) that is positioned further away from the outer face. The structural member provides improved use of timber raw material in the manufacture of the structural member, as well as improved strength and/or reduced variation in strength between different beams. In particular, in the layer having the smaller number of annual rings, those lamellae may have a greater average annual ring radius of curvature than the lamellae of the layer that is positioned further away from the outer face. Hence, the outer layer will have higher strength. A method of forming a structural member is also disclosed.
Description
A structural member (10), such as a beam, a stud or a joist, is disclosed. The structural member ses a plurality of glued-together wood lamellae (20a, 20b), each having a a cross section which is parallel with a cross section of the structural member (10) and a longitudinal direction which is parallel with a longitudinal direction of the structural member and with a principal grain direction of the wood lamellae (20a, 20b). In the structural member, the lamellae (20a, 20b) are formed as radial sections of a log and present cross sections which are triangular or oidal and present a respective base surface (bs1) that is formed at a ly outer part of the log. The lamellae (20a, 20b) are arranged as at least two glued-together layers (L1, L2, L3) in which base surfaces (bs1) of a pair of immediately adjacent lamellae (20a, 20b) face opposite directions. The base surfaces (bs1) are perpendicular to the bending direction (B) ed by a vertical load of the structural member (10). A layer (L1) that is positioned closer, as seen in the main bending direction, to an outer face of the structural member presents a smaller number of annual rings than a layer (L2) that is positioned further away from the outer face. The structural member provides improved use of timber raw material in the cture of the ural member, as well as improved strength and/or reduced ion in strength between different beams. In particular, in the layer having the smaller number of annual rings, those lamellae may have a greater average annual ring radius of curvature than the lamellae of the layer that is positioned further away from the outer face. Hence, the outer layer will have higher strength. A method of forming a structural member is also disclosed. 728649 B2 A GLUELAM URAL MEMBER AND A METHOD OF PRODUCING SUCH A GLUELAM STRUCTURAL MEMBER Technical Field The present disclosure relates to a structural member, which may be used as a beam, a joist, a stud, a pillar or the like. The disclosure also relates to a method of producing the structural member.
Background Currently, glue-laminated beams lam") in Europe are mostly produced according to DIN 1052:2008 (German standard) or DIN EN 14080: 2013-09 (harmonized European standard). The beams 1 (Fig. 1) are built up with visually graded or machine graded boards 2, which are produced and kiln-dried in ls in the traditional way.
The gluelam producer takes these boards as raw material, grades them and produces the ed lamellae by cutting out defects (e.g. knots) and finger-jointing 3 the pieces together. After the finger-jointed lamellae 2 have been planed, glue is applied and the beam 1 is formed by gluing the lamellae 2 together. The final steps may comprise planing the beam, ng optical defects, packaging and loading it.
Hence, traditionally, timber is sawn into planks or ae according to the scheme depicted in Fig. 1 of US5816015, which discloses alternative methods of forming wood beams by laminating together a plurality of planks or lamellae.
EP1277552A2 discloses a similar method of forming a wood beam by cutting a round piece of timber into a ity of strips having a trapezoidal cross section and laminating together the pieces thus formed into a beam.
US4122878 discloses a method of converting balsa wood of relatively small diameter into panels.
There is still a need to provide improved use of the timber raw material, as well as a need for beams having improved strength and/or reduced variation in strength n different beams.
Summary It is a general object of the present invention to provide an ed structural member, such as a beam, a joist, a stud, a pillar or the like. A particular object includes the provision of a structural member which makes better use of existing raw materials and which is stronger. Further objects e the provision of improved control of the production process of structural members, such that properties of resulting members will present less variation.
The invention is defined by the appended independent claims. Embodiments are set forth in the dependent claims, in the following ption and in the attached According to a first aspect, there is provided a structural , such as a beam, a stud or a joist, presenting a predetermined main bending ion. The structural member comprises a ity of glued-together wood lamellae, each having a lamella cross section which is parallel with a cross section of the structural member and a longitudinal direction which is parallel with a longitudinal direction of the structural member and with a principal grain direction of the wood ae. The lamellae are formed as radial sections of a log and present cross sections which are triangular or trapezoidal and present a respective base surface that is formed at a radially outer part of the log. The ae are arranged as at least one layer in which base surfaces of a pair of immediately nt lamellae face opposite directions. The base surfaces are perpendicular to the bending direction.
The term "trapezoid" is the American h equivalent of the British English term "trapezium". The term "trapezoid is defined as a convex quadrilateral with one pair of parallel sides, referred to as "bases" and a pair of non-parallel legs.
The term "bending direction" can be replaced with "transversal load direction", which is perhaps more relevant for the case where the structural member is in the form of a beam which receives a transversal load over all or part thereof.
The invention is thus based on the understanding that strength properties (tensile as well as g strength) increase radially from pith to bark. Hence, the youngest (i.e. most outside lying) wood is the most valuable in terms of strength properties. While today’s sawmilling technology results in most of the outside lying wood being ted into chips and not into sawn-goods, the present ion provides for an enhanced use of the most valuable wood, since the inventive concept will result in the forming of pieces of wood which will always include the outermost part of the log.
It is estimated that beams formed according to the present disclosure can achieve about 10 % increase in strength ties given the same amount of raw material used.
The ae may have the shape of an les triangle and/or of an isosceles trapezoid.
Although other cross sections are possible, including varying or alternating cross sections, an isosceles trapezoid shape for all lamellae would appear to be the most practical one from a production perspective.
In the lamellae, an annual ring radius of curvature may decrease with an increasing distance from the base surface.
Hence, the youngest portion of the wood will be present at the major base surface and the age of the wood will increase gradually towards the minor base surface or towards the triangle apex, as the case may be.
The structural member ses at least two glued-together layers of lamellae that are ed such that base surfaces of a pair of immediately adjacent lamellae face opposite ions.
Hence, the present sure provides a modular approach to the design of structural members in that standardized building blocks may be used to form a y of structural members having different properties.
The layers may present different thickness as seen in a direction perpendicular to the base surfaces.
A layer that is positioned closer, as seen in the bending direction, to an outer face of the structural member presents a smaller number of annual rings than a layer that is positioned further away from the outer face.
In the layer having the smaller number of annual rings, those lamellae whose base surfaces face the same direction and which tute the greatest part by volume of that layer, may have a greater average annual ring radius of curvature than the lamellae of the layer that is positioned further away from the outer face.
Hence, the outer layer will have higher strength.
The lamellae may be formed of pieces of wood that are radial sectors of a log having their respective apex and arc portions cut away.
The ae may present a trapezoidal cross section, and the major base surfaces of the lamellae may present less cut-off wood fibers per area unit than the minor base surfaces of the lamellae.
Hence, the wood fibers at the major base surface will be intact to a higher degree than the wood fibers at the minor base surface. This means that the quality of the wood fibers having the greatest th will be preserved and maximum use will be made of the nt strength of the raw material.
At least one of the lamellae may be formed by at least two pieces of wood, which are joined together short side to short side, preferably by means of a finger joint.
According to a second aspect, there is provided a gluelam beam comprising a structural member as described above, wherein the beam has an te cross section presenting a horizontally oriented short side, wherein the base surfaces are parallel to the short side.
According to a third aspect, there is provided use of a structural member as described above as a beam, a joist, a stud, a pillar or a wall element.
A beam in this regard may be a straight horizontal beam or a slanted beam, i.e. a beam having an angle of 0˚-90˚ ve to a horizontal direction.
A beam may also be curved.
A wall element may be used to provide all or part of a wall. Typical wall elements may have a height ponding to a desired room height, lly about 2.1 - 4 m, perhaps most likely in the range of 2.2 - 3 m. A width of such a wall element may be e.g. from 0.6 m to 25 m, perhaps most likely 0.6 - 15 m or 0.6 – 6 m.
According to a fourth aspect, there is provided a method of forming a structural member, such as a beam, a stud or a joist, presenting a predetermined main bending direction. The method comprises cutting a log along a principal grain direction of the log, into a plurality of wood lamellae which are triangular or trapezoidal in cross section and present a respective base surface that is formed at a radially outer part of the log.
The method further comprises arranging the lamellae as at least one layer in which base surfaces of a pair of immediately adjacent lamellae face opposite directions, and gluing together the lamellae along long sides thereof. The method also comprises arranging the ae such that the base surfaces are perpendicular to the bending In the method, the lamellae may be formed with an isosceles triangular or an isosceles trapezoidal cross section.
The forming of the lamellae into trapezoid cross section may comprise ng a respective major base e of the lamella to be formed with an ost surface of the log, such that less wood fibers per area unit are cut off at the major base surface than at a minor base surface.
The method may comprise a drying step, wherein the lamellae are dried, preferably kiln-dried, to a moisture t suitable for lamination.
The method may further comprise a planing step, wherein the lamellae and/or the layers are planed to provide a sufficiently plane surface for lamination.
The method may comprise cutting away a portion of the layer comprising the base surfaces and gluing this portion to an opposing side of the layer or to a part of another layer forming part of the ural member and being parallel with the cut away portion.
According to yet another ive concept, there is provided a building component, such as a beam, a stud, a joist or a sheet, comprising a plurality of gluedtogether wood lamellae, each having a a cross section which is parallel with a cross section of the structural member and a longitudinal direction which is parallel with a longitudinal direction of the structural member and with a principal grain direction of the wood lamellae. The lamellae are formed as radial sections of a log and present cross sections which are trapezoidal and present a respective base surface that is formed at a radially outer part of the log. The ae are arranged as at least one layer in which base surfaces of a pair of immediately adjacent lamellae face opposite ions. Major base surfaces of the lamellae present less cut-off wood fibers per area unit than minor base surfaces of the lamellae.
Hence, the wood fibers at the major base surface will be intact to a higher degree than the wood fibers at the minor base surface. This means that the quality of the wood fibers having the greatest th will be ved and maximum use will be made of the inherent strength of the raw material.
This second inventive concept may be used with or without base surfaces that are are perpendicular to a bending direction or transversal load direction of the building component.
In the lamellae, an annual ring radius of ure may decrease with an increasing distance from the base e.
Hence, the youngest portion of the wood will be present at the major base surface and the age of the wood will increase gradually towards the minor base surface or towards the triangle apex, as the case may be.
The building component may comprise at least two glued-together layers of lamellae that are arranged such that base surfaces of a pair of ately adjacent lamellae face opposite directions.
Hence, the present disclosure provides a modular approach to the design of ng components in that rdized building blocks may be used to form a variety of building components having different properties.
The layers may present different ess as seen in a direction perpendicular to the base surfaces.
A layer that is positioned closer, as seen in a g direction or transversal load direction, to an outer face of the building component presents a smaller number of annual rings than a layer that is positioned further away from the outer face.
In the layer having the smaller number of annual rings, those lamellae whose base surfaces face the same direction and which constitute the greatest part by volume of that layer, may have a greater average annual ring radius of curvature than the lamellae of the layer that is positioned further away from the outer face.
Hence, the outer layer will have higher strength.
The lamellae may be formed of pieces of wood that are radial sectors of a log having their respective apex and arc portions cut ccording to a second aspect of the second inventive concept, there is provided use of a building component as bed above as a beam, a joist, a stud, a pillar or a wall element.
According to a third aspect of the second inventive concept, there is provided a method of forming a building component, such as a beam, a stud, a joist or a sheet, ting a predetermined main bending direction. The method ses cutting a log along a principal grain direction of the log, into a plurality of wood lamellae which are trapezoidal in cross section and present a respective base surface that is formed at a radially outer part of the log. The method r comprises arranging the lamellae as at least one layer in which base surfaces of a pair of immediately adjacent lamellae face opposite directions, and gluing together the lamellae along long sides thereof.
The forming of the lamellae into trapezoid cross section comprises aligning a respective major base surface of the lamella to be formed with an outermost surface of the log, such that less wood fibers per area unit are cut off at the major base e than at a minor base surface.
Brief ption of the Drawings Fig. 1 schematically illustrates a prior art gluelam beam.
Fig. 2 schematically illustrates a gluelam beam according to the present inventive concept.
Figs 3a-3c schematically illustrate different embodiments of gluelam beams according to the t inventive concept.
Fig. 4 schematically illustrates a part of a layer of a gluelam beam according to the present inventive concept.
Fig 5a-5c schematically illustrate different embodiments of gluelam beams according to the present inventive concept.
Figs 6a-6j schematically illustrate steps which may be used in the production of a gluelam beam according to the present inventive concept.
Detailed Description In the present sure, the inventive concept will be illustrated with reference to a beam 10, which presents a cross section and a longitudinal direction L, and which will typically be intended to receive and support one or more loads, which may be distributed more or less evenly over all or parts of the longitudinal direction of the beam 10. In most cal situations, the force will be vertical, and so the vertical bending of the beam 10 will be the most relevant.
The cross section may, as illustrated in Fig. 2, be substantially rectangular with short sides of the rectangle being substantially horizontal. For simplicity, the surfaces defined by the short sides will be referred to as "upper side" and "lower side". The long sides of the rectangle define side surfaces of the beam. Such a beam may be arranged substantially horizontally, or it may extend more or less at an angle to the horizontal direction, for example to t a staircase, a roof, etc. As yet another example, the beam may be curved, for e to support a curved roof.
Fig. 2 thus schematically illustrates a beam 10, which is formed of three layers L1, L2, L3 of lamellae 20a, 20b. A bending direction B is rated as the ion in which a l transversal load will act upon the beam 10. Hence, for a beam which is subjected to a transversal load (e.g. a dicularly oriented load), the bending direction B will coincide with the transversal load direction.
The lamellae 20a, 20b present a respective cross n, which, in the illustrated example, has the shape substantially of an isosceles oid, which is the result of the lamellae being formed by radially sectioning a log or a piece of timber.
Each lamella cross section will thus present a pair of bases b1, b2 defining tive base surfaces bs1, bs2 of the lamellae 20a, 20b and a pair of legs l1, l2 defining respective side surfaces ss1, ss2 of the lamella 20a, 20b. The base surfaces bs1, bs2 comprise a major base surface bs1 and a minor base surface bs2. In each lamella, the major base surface bs1 is formed at an outer portion of the log, closer to the bark than to the pith and the minor base surface bs2 is formed at an inner portion of the log, closer to the pith. It is preferable to provide the longitudinal sides of the major base surface bs1 to coincide with the l surface of the useful part of the log (i.e. the outermost part of the log when the bark has been cut away.
The lamellae 20a, 20b in each layer L1, L2, L3 are arranged side surface ss1 to side surface ss2 with major base surfaces bs1 of immediately adjacent lamellae 20a, 20b facing opposite directions.
Hence, in e.g. the uppermost layer L1 of Fig. 2, the upwardly facing e of the beam 10 , will be formed by major base surfaces bs1 and minor base surfaces bs2, which are presented ating as seen in a width direction of the beam 10. The ly and/or downwardly facing surface of the beam may thus consist essentially to at least 50 %, preferably at least 60 %, at least 70 %, at least 80 %, at least 90 %, at least 95 % or at least 98 %, of the major base surfaces bs1.
Fig. 3a schematically rates the simplest form of beam or joist that can be formed ing to the present inventive concept, with a single layer of lamellae 20a, 20b which are laminated side by side with major base surfaces bs1 facing alternating upwardly and downwardly, respectively.
Fig. 3b schematically illustrates a two-layer beam or joist that can be formed according to the present inventive concept. This beam is thus formed by two layers L1, L2 of lamellae, each of which are formed according to what has been discussed above with reference to Figs 2 and 3a. The layers L1, L2 may be laminated together by gluing using conventional gluing technique. In order to provide a longer structural member, it is possible to join together layers L1, L2 of lamellae, e.g. by finger ng, prior to the joining of the layers. L1, L2 to form the structural member.
Fig. 3c schematically illustrates a layer beam or joist that can be formed according to the present ive concept and similarly to that of Fig. 3b. Hence, in this embodiment, the beam is formed of three layers L1, L2, L3 of lamellae 20a, 20b, each layer being formed as disclosed above with reference to Figs 2, 3a and 3b.
Each layer may typically have a thickness of about 5-20 cm, preferably about 10- cm. A beam may be formed of as many layers as deemed ary. Current standard beams are available at a height of up to 1.2 m, which would translate into a beam having 6-24 layers. Most likely, a beam of that height would have 10-12 layers.
Fig. 4 schematically illustrates an enlarged view of the product illustrated in Fig. 3a. As the uppermost and lowermost portions are formed mainly by the outer wood, i.e. the younger wood, high strength zones HS will be provided at the uppermost and lowermost portions, while a middle strength zone MS will be provided in between.
As can be seen in Fig. 4, the high strength zones HS will consist mainly of wood from the outermost part of the log. This would then provide an optimal beam, as it would be the strength of the uppermost and lowermost portions that would be decisive for the g strength of the beam.
Visually, the zones HS, MS can be distinguished by the radius of curvature of the annual rings: the high strength zone HS will have a larger proportion of annual rings having a greater radius of curvature than the middle th zone MS.
It is currently not possible to provide a clear limit on what is a high strength zone and what is a middle strength zone. The decision on how to define the zones may be based on experimental strength data and on due regard to the cost of carrying out the "moving" operation.
In Fig. 5a, there is illustrated the case of Fig 3a, which will thus present high strength zones at the upper and lower surfaces and a middle strength zone in between.
As is illustrated in Fig. 5a, a high strength zone HS may be cut away, e.g. by sawing at the line C1, and moved, as will be discussed below.
In Fig. 5b, there is illustrated an embodiment wherein the beam or joist is formed of four layers L1’, L2’, L3’, L4’: a pair of central layers L2’, L3’ and a pair of outermost layers L1’, L4’. It is noted that the most lly d high strength zones HS of the central layers L2’, L3’ have been removed and laminated as outermost layers L1’, L4’.
Hence, effectively, the high strength zones HS have been moved from a l location, where they are of less use, to an outermost location, where better use will be made of their strength.
These moved high strength zones will appear as outer layers that have smaller thickness in the vertical direction than the l layers L2’, L3’. For example, an average radius of ure of the annual rings of the outer layer L1’, L4’ lamellae may be greater than an average radius of ure of the central layers L2’, L3’.
In Fig. 5c, there is illustrated a concept similar to that of Fig. 5b, but with the beam or joist having three l middle strength zones MS and six outer high strength zones HS, each outer layer being formed by "moving" the centrally located high strength zones HS.
The description will now be directed towards a method for production of the beam described above. As mentioned above, the number of layers to be included in the beam is a matter of selection.
In Fig. 6a, there is illustrated a log 100 which has been longitudinally cut in half and then radially sectioned into six segments 200, i.e. 12 segments per log. Hence, each segment will have an apex angle of 30˚. It is noted that the number of segments into which each log will be ned may be ed according to what is deemed appropriate. As a rule of thumb, the greater the log diameter, the greater the number of segments. As another example, 16 segments may be a suitable alternative, with the apex angle then being 22.5˚.
As examples, the starting material 100 may be a complete log or a longitudinally cut log (as illustrated in Fig. 6a). The log may be regarded as cylindrical (or semicylindrical ) or as a ted cone. In any event, the starting material is radially sectioned, whereby a plurality of lamellae blanks 200 are provided, the cross sections of which being in the form of a segment of a circle.
When g the log, it is possible, and perhaps most practical, to form the segments as les trapezoids, as discussed above. However, it is also possible to form the segments with other shapes, such as triangles, trapeziums or trapezoids, and to te such shapes together with an ensuing planing step that will provide the final shape of a layer L1, L2, L3.
In Fig. 6b, there is illustrated a step in which the lamellae blanks 200 prepared in the preceding steps are laid up for drying. The drying process may be any known type of drying process, e.g. a kiln-drying process and the segments 200 may be dried to a moisture content that is suitable for the lamination process that is to be used. There are many different techniques for stacking lamellae, and many different techniques for drying, and no limitation is intended in this regard.
In Fig. 6c, there is illustrated a step of fication and removal (cutting away) of defects, such as knots. Processes for identifying and managing defects in wood are known from e.g. US8408081B2 and EP1355148. Parts of the lamellae blanks 200 that are deemed to have insufficient th may thus be identified and removed, e.g. by cutting away the entire portion of the ae blank 200 that is affected by the defect.
In Fig 6d, there is rated a step of optimizing the lamellae. In this step, lamellae blanks 200 are inspected and it is ined what will be the optimal ae cross section for each lamellae blank. As is illustrated in Fig. 6d, for lamellae blanks having the same original cross n it is possible to provide trapezoidal lamellae having, e.g. differently sized base surfaces and/or different heights. The selection of what cross section to e may depend on factors such as wood type and quality, occurrence of defects, etc.
In Fig. 6e, there is illustrated a step of formatting lamellae 20 from the lamellae blanks 200. In this step, the segment apex (i.e. the pith) and the segment arc (i.e. the bark or the portion closest to the bark) may be cut away to provide the desired triangular, trapezoidal or isosceles triangular or trapezoidal shape. The formatting may also include planing and/or profiling of the side edges and/or of the base surfaces. The formatting step is typically carried out to achieve the shape determined in the optimization step.
It is noted that while in traditional sawmill ce; a log is treated as a cylinder, wherein the smallest cross section of the log (typically the uppermost part of the log) will define the diameter of the cylinder.
However, a log is actually a truncated cone with a taper of generally about 5-7 mm/m tree height for Norway spruce in middle Europe. Other tapers may apply to different wood species and/or in different locations. Consequently, when using the traditional approach to ting a lamella, some of the most ble wood, close to the bark, will be cut away while the less desirable wood, closer to the pith, will be kept.
While the present inventive concept may very well be practiced using this traditional approach, another approach will be described.
In the formatting step, the major base surface bs1 of the trapezoid will be fitted as closely as possible along the outermost surface of the lamella blank, as is illustrated in the far right part of Fig. 6e. Consequently, less material will be cut away from the ost portion of the log and more material will be cut away from the portion closest to the pith.
In uence, more of the desirable wood will be kept.
As wood fibers actually run parallel to the bark (i.e. the envelope of a truncated cone) rather than along the length direction, of a log (which would assume the log is a cylinder), the traditional method will lead to a lot of wood fibers being cut off at the major base surface bs1. Thus, for each area unit of the base surface, there will appear more cut off wood fibers at the major base surface than at the minor base surface bs2.
However, with the herein described , there will be less cut off wood fibers per area unit at the major base e than at the minor base surface, thus resulting in more of the valuable wood being retained where it is needed. Phrased differently, the g of the most le part of the wood will be more el to the fiber direction than in the traditional method.
During the formatting step, the triangle or trapezoid may be taken at a radial distance from the pith which optimizes the use of the lamellae blank 200, bearing in mind that the lamellae blank, as a consequence of being formed from a starting material which is actually slightly frusto-conical in shape, may have a cross section which varies over its length. At the end of the formatting, a lamella in the form of a piece of wood having a prismatic shape with a trapezoidal cross section and a longitudinal direction parallel with the fibers at the outermost part of the log from which it was formed has been obtained.
In Fig. 6f, there is illustrated a step of providing an end portion of a segment with a finger joint. Joining of wood lamellae is known per se and the s may extend parallel with the base surfaces of the isosceles trapezoid, parallel with a side surface of the trapezoid or parallel with a central radius of the lamella blank 200 from which the lamella is formed.
In Fig. 6g, there is illustrated an alternative way of providing the finger joint. In this step, the fingers will extend along a side e of the trapezoid, which may be advantageous for lamellae having a relatively high and narrow cross section as the lamella would rest more stably on the support when the fingers are being cut.
Other types of joints may be used, with a ence for a joint that only involves the use of wood and glue.
In Fig. 6h, there is rated a finished lamella, which is formed of a plurality of joined together segments. If the side edges have not previously been planed or ted, or additional planing or formatting is called for, a side edge planing step may be provided at this point.
In a non-illustrated step, the finished lamella are arranged with base surfaces bs1, bs2 of immediately adjacent lamellae 20a, 20b facing opposite directions, whereupon the lamellae 20a, 20b are glued er side surface ss1 to side surface ss2 to form a sheet 201 having a pair of opposing major surfaces which are formed by the base surfaces bs1, bs2 of the lamellae 20a, 20b. In this step, the sheet illustrated in Fig. 6i is provided. That sheet 201 may be used as is, or further converted, as will be described below.
In Fig. 6i, there is illustrated a step of sawing the sheet 201 formed in the preceding step into a plurality of planks 202 having the approximate width of the beam that is to be formed.
In one ment (e.g. Fig. 3a, 5a), the beam or joist may be ready at this point, with optional steps of planing and/or grinding remaining.
In a non-illustrated step, the planks 202 thus ed may be stacked major e to major surface and glued together to form a beam blank 203.
In one embodiment of the invention (e.g. Fig. 3b, 3c), each beam 10 may be formed by a predetermined number of planks. Hence, at this point, the beam may be ready, with optional steps of planing or ng remaining.
In Fig. 6j, there is illustrated a step of sawing the beam blank 203 into beams 10 of suitable height.
While the present disclosure has been given with nce to a beam, which is intended to receive a vertical load, which is distributed over all or part of a length of the beam, it is understood that the subject matter of the present disclosure may also be applied to e.g. floor joists, wall studs, pillars and the like.
Typically, a layer having base surfaces which are parallel to an outermost surface of the ural member can be applied to each longitudinal side of, e.g., a pillar, joist, stud or the like, having a polygonal cross section (such as rectangular, square, pentagonal, hexagonal, etc.) or any other cross section, such as circular or otherwise curved.
For example, in the case of a , multiple bending directions may be defined (typically four for a square or rectangular cross section pillar), whereby a layer L1, L2, L3 may be provided on each side surface of the pillar.
It should also be noted that the sheets rated in Figs 6i and 6j may be used as they are shown in the respective figure, for example where a building component, such as a ural board or a wall element, is desired. Board materials may be produced measuring e.g. about 3x15 m with a thickness of 10-20 cm, preferably 10-14 cm. Such boards may be used for constructing walls or wall segments, floors or floor segments and/or ceilings/roofs or ceiling/roof segments.
I/WE
Claims (13)
1. A structural member (10), such as a beam, a stud or a joist, presenting a predetermined main bending direction (B), sing: a plurality of glued-together wood lamellae (20a, 20b), each having a lamella cross section which is parallel with a cross section of the structural member (10) and a longitudinal direction which is el with a longitudinal direction of the structural member and with a pal grain direction of the wood lamellae (20a, 20b), wherein the lamellae (20a, 20b) are formed as radial sections of a log, n the ae (20a, 20b) present cross sections which are triangular or trapezoidal and present a respective planar base surface (bs1) that is formed at a radially outer part of the log, wherein the base surfaces (bs1) are perpendicular to the main g direction wherein the structural member comprises at least two glued-together layers (L1, L2, L3) of lamellae (20a, 20b) that are arranged such that base surfaces (bs1) of a pair of immediately adjacent lamellae (bs1) face opposite directions, and wherein a layer (L1) that is positioned closer, as seen in the main bending direction, to an outer face of the structural member presents a smaller number of annual rings than a layer (L2) that is positioned further away from the outer face.
2. The structural member as claimed in claim 1, n the lamellae (20a, 20b) have the shape of an isosceles triangle and/or of an isosceles trapezoid.
3. The structural member as claimed in claim 1 or 2, wherein, in the lamellae (20a, 20b), an annual ring radius of curvature decreases with an increasing distance from the base surface (bs1).
4. The ural member as claimed in claim 1, wherein the layers (L1, L2, L3) present different thickness as seen in a direction perpendicular to the base surfaces (bs1).
5. The structural member as claimed in claim 1, wherein, in the layer (L1) having the smaller number of annual rings, those lamellae (20a; 20b) whose base surfaces (bs1) face the same direction and which constitute the greatest part by volume of that layer (L1), have a greater average annual ring bending radius than the lamellae of the layer (L2) that is positioned further away from the outer face.
6. The structural member as claimed in any one of the ing claims, wherein the lamellae (20a, 20b) are formed of pieces of wood that are radial sectors of a log having their tive apex and arc portions cut away.
7. The structural member as claimed in any one of the preceding claims, wherein the lamellae (20a, 20b) present a trapezoidal cross section, and wherein the major base surfaces (bs1) of the lamellae present less cut-off wood fibers per area unit than the minor base surfaces (bs2) of the lamellae.
8. A gluelam beam (10) in the form of a structural member as claimed in any one of the preceding claims, wherein the beam has an elongate cross section presenting a horizontally oriented short side, n the base surfaces (bs1) are el to the short side.
9. Use of a structural member as claimed in any one of claims 1-7 as a beam, a joist, a stud, a pillar or a wall element.
10. A method of forming a structural member, such as a beam, a stud or a joist, presenting a predetermined main bending direction (B), the method comprising: g a log (100), along a principal grain direction of the log, into a plurality of wood ae (20, 20a, 20b, 200), arranging the ae (20, 20a, 20b, 200) as at least two layers (L1, L2, L3) in which planar base surfaces (bs1) of a pair of immediately adjacent lamellae (20a, 20b) face opposite directions, and gluing together the lamellae (20a, 20b) along long sides (ss1, ss2) thereof, wherein cutting the log (100) comprises cutting the log (100) such that the plurality of wood lamellae (20, 20a, 20b, 200) are triangular or trapezoidal in cross section and present a respective planar base surface (bs1) that is formed at a radially outer part of the log (100), wherein arranging the lamellae comprises arranging the lamellae (20a, 20b) such that the base surfaces (bs1) are perpendicular to the main bending ion (B), and such that a layer (L1) that is oned closer, as seen in the main bending direction, to an outer face of the structural member presents a smaller number of annual rings than a layer (L2) that is positioned further away from the outer face.
11. The method as claimed in claim 10, n the lamellae (20a, 20b) are formed with an les triangular or an isosceles trapezoidal cross section.
12. The method as claimed in claim 11, wherein the g of the lamellae into trapezoid cross section comprises aligning a respective major base surface (bs1) of the lamella to be formed with an outermost surface of the log, such that less wood fibers per area unit are cut off at the major base surface (bs1) than at the minor base e (bs2).
13. The method as claimed in any one of claims 10-12, further comprising cutting away a portion of the layer (L1, L2, L3) comprising the base surfaces (bs1) and gluing this portion to an opposing side of the layer (L1, L2, L3) or to a part of another layer (L1, L2, L3) forming part of the structural member and being parallel with the cut away portion. Stora Enso Oyj By the Attorneys for the Applicant SPRUSON & FERGUSON
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE1450929-3 | 2014-08-08 | ||
SE1450929A SE538283C2 (en) | 2014-08-08 | 2014-08-08 | A gluelam structural member and a method of producing such agluelam structural member |
PCT/IB2015/055934 WO2016020848A1 (en) | 2014-08-08 | 2015-08-05 | A gluelam structural member and a method of producing such a gluelam structural member |
Publications (2)
Publication Number | Publication Date |
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NZ728649A NZ728649A (en) | 2022-03-25 |
NZ728649B2 true NZ728649B2 (en) | 2022-06-28 |
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