Classifications

• • 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
  • E04C3/29—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces built-up from parts of different material, i.e. composite structures
  • E04C3/292—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces built-up from parts of different material, i.e. composite structures the materials being wood and metal
• • 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
  • E04C3/18—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members with metal or other reinforcements or tensioning members

Definitions

• the present invention relates generally to wood structural material, and specifically relates to a method of producing a wood structural member as specified in the preamble of the accompanying claim 1 , a wood structural member according to the preamble of the accompanying claim 12, and a use according to claim 24.
• Glued-laminated wood is a product that may briefly be said to consist of a number of wood laminations that are stacked on top of each other and are glued to each other. Such products have been used for several years, mainly as structural members in different kinds of building or construction work.
• the main advantages of employing glued-laminated wood structural members in general, and not least as supporting members in buildings, are on the one hand that employing the different adhesively joined laminations minimizes the weakening effect of defects within the wood.
• such glued-laminated wood structural members have a significantly improved resistance to fire than both other types of wood structures and steel beams or corresponding structural members. Furthermore they have an aesthetically appealing appearance and are dimensionally stable.
• Patent Specification No. 5 050 366 does indeed disclose a suggestion for strengthening a glued-laminated wood beam by introducing a number of rods into the interior of the beam, but in this case the specific purpose is likewise to strengthen the upper and lower regions of the beam.
• the rods are positioned in grooves milled in separate or adjacent laminations. Apart from the fact that such a solution does not provide any uniform or evenly distributed reinforcement the milled grooves cause an undesirable weakening of the individual laminations that are provided with such grooves. To our knowledge, said product has not come to practical use in any greater extent, and this is probably also due to the difficulties of providing a rational and thereby economical production.
• a basic object of the invention is to provide a simple method of strengthening or reinforcing a glued-laminated wood structure. More specifically the object is to achieve this by providing a method of producing a glued-laminated wood structural member by means of which a strengthening is obtained that is uniform and relatively evenly distributed in the structural member. Expressed otherwise, the aim is to increase the applicability of such wood structural members by reducing the difference in dimensions between such structural members and for instance steel beams having equal strength.
• the invention is based on the understanding that the strength of a structural member of a given dimension and of the specified kind can be greatly increased by providing a steel reinforcement in the interior of the member, said reinforcement extending over substantially the entire height and length of the member.
• this is achieved by stacking wood segments on top of each other and gluing them to each other in at least two essentially parallel stacks, by providing a steel plate between the stacks or between at least two of the stacks and by adhesively fixing the steel plate to each of the stacks being adjacent thereto, as is specified in the characterizing portion of claim 1.
• This provides an integral, composite structural member that with a marginally increased weight has significantly improved strength properties with regard to different load conditions.
• a steel plate is chosen having a dimension essentially corresponding to the height and length of the stacks. Said steel plate is glued to the stacks as stated in the characterizing portion of claim 2.
• a structural member is obtained having a reinforcement that is evenly distributed over its entire height and length.
• a steel plate is chosen having a dimension being smaller than the height and length of the stacks, and is glued to the stacks, as stated in the characterizing portion of claim 3.
• a structural member is obtained where the strengthening or reinforcement is still evenly distributed over the main portion of its height and length, but where a possibility is simultaneously created of providing the steel plate or plates recessed in the member, as is stated the characterizing portion of claim 4.
• Such an embodiment is particularly applicable in an aggressive environment since the steel plates are protected from the environment or surroundings.
• a wood structural member employing the principles of the present invention is provided.
• the structural member of the invention comprises at least two substantially parallel stacks of segments that are glued to each other and a steel plate that is glued to the adjacent stacks. Together they form a composite, integral unit.
• a further aspect of the invention concerns a use of a wood structural member designed in accordance with the basic principles of the invention as a supporting or load-carrying member of a construction work.
• Fig. 1 is a partial perspective view of a wood structural member built up in accordance with the basic principles of the invention
• Fig. 2 is an end view of the wood structural member as illustrated in fig. 1 ,
• Fig. 3 illustrates an alternative embodiment of a wood structural member according to the invention
• Fig. 4 is a partial perspective view of a further variant of a steel plate intended for use in a structural member according to the invention
• Fig. 5a-c are partial, partly schematical end views of further embodiments of a structural member according to the invention, employing profiled steel plates
• Fig. 6 is an end view of a further embodiment of the wood structural member according to the invention
• Fig. 7 is a side view of the embodiment of fig. 6, and
• Fig. 8 illustrates a stack of laminations or segments in the structural member according to figs 6 and 7, in a cross-section along the line A-A in fig. 7.
• the basic object of the invention is to provide such an assembled structural member 1 having a unitary reinforcement being relatively evenly distributed in the member.
• this is achieved by forming two separate stacks 3a and 3b of segments 2 positioned on top of each other and glued to each other.
• a strengthening or reinforcing member in the shape of a steel plate 4 is positioned between the stacks 3a, 3b and is glued to their side surfaces facing each other.
• the invention is not restricted to the use of only two stacks 3a, 3b of wood segments 2.
• a greater number of parallel stacks may be used, as is indicated at 3a' and 3b' in fig. 2 and also in drawing figure 6 that is more closely described below.
• the invention makes it possible to selectively, for instance depending upon the actual load condition of a structural member 1 , provide steel plates 4 between only two, several or all adjacent stacks, and this is indicated in the embodiment that is illustrated in figs. 6-8 and is described in detail below.
• the embodiment having more than two stacks 3a', 3b', as indicated in fig. 2 illustrates a central positioning of the only steel plate 4, it lies within the scope of the invention to provide the steel plate or plates asymmetrically with respect to the center plane of the member 1 , that is between optional stacks. This may likewise be done for instance depending upon the actual load condition.
• segments 2 of a corresponding size may be stacked on top of each other and glued to each other.
• the manufacturing can be made more rational by forming a single stack from segments having a dimension corresponding to the total dimension of the structural member 1, that is with reference to the width of fig. 2.
• the segments have been glued to each other they are cut up to a desired number of stacks that are subsequently glued to each other or to an intermediate steel plate 4. It is obvious that with such a method the material that disappears through the kerf must be considered in connection with the dimensioning.
• the dimensional increase caused by the introduction of the steel plate/plates must also be considered, except by the embodiment according to figs. 6-8.
• the invention as such is not restricted to the use of specific material qualities or grades.
• the steel plate 4 this may be manufactured from a steel grade corresponding to the strength requirements that apply to the specific application.
• high strength materials may be considered in connection with very high requirements for strength or where small dimensions are required, and a stainless steel may be employed in the case where the member 1 shall be used in an aggressive environment.
• the segments 2 may be manufactured from materials usually used within this field. In order to meet specific strength requirements it is likewise possible to employ particularly strong wood. In situations where very high demands are set for strength and/or resistance to external influence it may thereby be interesting to use the compressed wood manufactured by Lign Multiwood AB.
• each segment 2 can be impregnated throughout prior to being glued together. This may be done by employing a very effective and also environment-friendly impregnation method that has likewise been developed by Lign Multiwood AB.
• the sides of the stacks 3 a, 3 b are glued to the steel plate 4 by means of flexible glue of a suitable composition, and in order to increase the adhesion against the plate 4 the plate surface may when required be treated in various manners, such as by blasting, anodizing, metal plating or other surface treatment.
• the plate 4 may be provided with through openings distributed across its surface. Said openings likewise contribute to strengthening the bond between the stacks 3 a, 3 b and the steel plate 4 and thereby to strengthening the entire member 1.
• FIG. 3 illustrates a profiled steel plate 4a having the general shape of an I- beam, whereby the web 6 of the I-beam shape is glued to the stacks 13a, 13b and the upper and lower cross pieces 7, 8 of the I-beam shape are glued to the uppermost and lowermost, respectively, segments 2 of the adjacent stacks.
• the cross pieces 7, 8 could be narrower than the width of the stacks 13a, 13b, as seen in the drawing figure, but they preferably have a width corresponding to the total width of the structural member 1. Such a design provides a good holding together of the member la and is particularly useful in the cases where, for esthetical reasons, a visible wood surface is not required around the entire member la.
• Fig. 4 illustrates a variant of a steel plate 4b having V-shaped punched portions 9a, 9b distributed across its surface. After having been punched said portions are bent outwardly substantially normal to the plate 4b surface, forming gripping teeth 11.
• the gripping teeth 1 1 are alternately bent outwardly to different sides of the plate 4b and accordingly only half of them are visible in the drawing figure.
• the gripping teeth 11 are pushed into the corresponding stack for providing a mechanical interlock between the stacks and the plate.
• Drawing figures 5a-c illustrate a further example of the use of a profiled steel plate in a structural member according to the invention.
• the profiled steel plate 4c, 4d, 4e serves the double purpose of on the one hand increasing the strength of the plate and thereby of the structural member and on the other hand of strengthening the adhesion between the stacks 23a, 23b, 33a, 33b, 43a, 43b and the steel plate 4c, 4d, 4e by increasing the available glue surface.
• fig. 5a symbolizes the use of a "corrugated" plate 4c, for instance a so called slit plate, which is a type of profiled thin plate that has very high flexural rigidity.
• the sides of the stacks 23a, 23b being adjacent to the plate are profiled in the corresponding manner.
• Fig. 5b illustrates an alternative profiled plate 4d having right-angled bends, and corre- spondingly profiled sides of the adjacent stacks 33a, 33b, whereby the a kind of finger joint is formed with the intermediate plate profile.
• the "fingers" of the stacks are in this case formed by every other lamination or segment of the stacks, which facilitates manufacturing.
• Fig. 5c illustrates a variation having a wave-shaped plate profile 4e and correspondingly profiled sides of the stacks 43a, 43b.
• figs. 6-8 illustrate an embodiment of the invention that is particularly suitable to use in the cases where the structural member lb shall be applied in an outdoor environment or in another aggressive environment that may have a negative effect upon the steel plate. From another aspect said embodiment is appropriate for use in cases where a visible steel plate would be considered disturbing the esthetical appearance of the structural member lb.
• the structural member lb is formed by four substantially parallel stacks 53a, 53b, 53c, 53d between which are received three steel plates 4f, said steel plates having a generally planar shape.
• Figs. 6 and 7 illustrate that in this embodiment the steel plates 4f have a dimension that is smaller than that of the assembled structural member lb as partially shown in fig. 7, both with regard to its width or height and its length.
• the steel plates 4f do in all directions terminate inside the outer surfaces of the structural member lb.
• the latter are provided with cut-in portions or recesses 54 illustrated in fig. 8, which shows a cross section, along the line A-A of fig. 7, through the stack 53a being positioned furthest to the left in the structural member lb of fig. 6.
• the stack 53a is an outer stack and is, like the other outer stack 53d, provided with only one cut-in portion 54 in one 55 of its side surfaces that is facing inwardly.
• the middle stacks 53b, 53c are provided with one cut-in portion in each side surface.
• the dimensions of the cut-in portions or recesses 54 are adapted to the overall dimensions of the plates 4f and they are centered in the respective side surface 55, that is they are at all sides surrounded by a remaining portion of the side surface 55.
• the height of the recesses 54 extends across all of the segments 2a-c of the stacks 53a-d, that is they terminate in the uppermost 2a and lowermost 2b segments respectively and are accordingly formed to be continuous, with respect to the height in fig. 8, in the middle segments 2c.
• Fig. 7 also illustrates that they are formed such that in the longitudinal direction they terminate at a corresponding distance from the ends of the structural member lb. Furthermore, they are each formed having a depth corresponding to or slightly exceeding half the thickness of the steel plate 4f, such that the two recesses 54 in the facing side surfaces of two adjacent stacks together form a pocket adapted to receive a steel plate 4f therein with a minimum of play.
• the illustrated embodiment discloses steel plates introduced between all of the stacks, it shall be emphasized that here also the number of steel plates and their positioning and thus also the number of recesses and their positioning may be varied optionally depending upon the desired properties.
• Characteristic of structural members manufactured in accordance with the principles of the invention is the evenly distributed, continuous strengthening or reinforcement thereof, which is obtained by the steel plate introduced between stacks of wood laminations.
• a structural member designed in accordance with the principles of the invention provides the following advantages over a typical conventional glued-laminated wood member:
• a significantly increased strength of the structural member - performed test show that a member according to the invention becomes approximately five times stronger than a conventional glued-laminated wood member having no reinforcement. • A significantly reduced dimension of the structural member, with maintained strength. • A possibility of "tailoring" the strength properties of the structural member by an alternative positioning of the steel plates as well as by choosing different steel grades and/or differently profiled steel plates.
• the invention is regarded having its primary use in connection with construction work, which is here regarded as including residential buildings, office buildings and industrial buildings as well as sports halls and bridges.

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• Engineering & Computer Science (AREA)
• Architecture (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Rod-Shaped Construction Members (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (2)

Citations (5)

Family Cites Families (2)

• 1999
  • 1999-03-15 SE SE9900918A patent/SE513499C2/sv not_active IP Right Cessation
• 2000
  • 2000-03-10 AU AU38509/00A patent/AU3850900A/en not_active Abandoned
  • 2000-03-10 WO PCT/SE2000/000469 patent/WO2000055445A1/en not_active Application Discontinuation
  • 2000-03-10 EP EP00917553A patent/EP1163404A1/en not_active Withdrawn

Patent Citations (5)

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