DE29606133U1 - Glulam made of star slats for use in structural timber construction - Google Patents

Description

PG/GP 8560-DE RALPH KIRST, Office for Timber Constructions, Irmenach

Glued laminated timber made from star lamellas for use in structural timber construction

The invention relates to a glued laminated timber made up of glued lamellas and a method for its production.

Conventional glued laminated timber beams, so-called glued laminated timber, have been manufactured for several decades and are used, for example in the form of beams, in practically all areas of structural timber construction. They are made up of so-called lamellae that are glued together and have three decisive advantages over conventional solid wood: firstly, they can be manufactured in any length and dimension, with lengths of up to around 40 m being common today, secondly, they are almost crack- and twist-free due to the prior drying of the individual lamellae and thirdly, due to their

Ralph KIRST - 2 - PG/GP 8560-DE

The structure and the glue joints can be subjected to 10% higher loads.

However, one disadvantage of the conventionally used glued laminated timber is that it is significantly more expensive than solid wood due to the complex process required for its production. In addition, there is an enormous loss of material from the round timber to the finished truss, which increases the price per cubic metre of glued laminated timber even further, and ultimately amounts to around three times the price of solid wood.

Another problem in the production of glued laminated timber is the selection of the individual lamellas. Due to the natural defects in its structure (knots, cracks, twisted grain, reaction wood, etc.), wood is not always equally resilient, which requires extremely careful pre-selection. Depending on the quality of the starting material, a considerable loss is therefore to be recorded here too if the required quality of the finished product is to be guaranteed.

A crucial point here is the so-called annual ring position. This is referred to as vertical or horizontal annual rings, whereby any conceivable intermediate angle is also possible. The higher the proportion of vertical annual rings, the higher the quality of the wood, as on the one hand the load-bearing capacity is greater and on the other hand the so-called swelling/shrinkage behavior of the lamella is more favorable. Wood swells or shrinks.
When the humidity changes, the wood shrinks radially only about half as much as it does tangentially, which causes the wood to warp when it dries.

The object of the invention is to provide a high-quality laminated timber which does not have the disadvantages known from the prior art.

This object is achieved by a glued laminated timber according to claims 1 to 8, which is made up of star or triangular lamellas and, due to its more favourable annual ring position, can be subjected to significantly higher static loads than a conventional glued laminated timber. The inventive

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Glued laminated timber can also be produced with significantly lower
costs than the well-known glued wood trusses.

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The invention is explained in more detail with reference to the following figures.

Figure \ shows schematically the conventional cutting process for producing rectangular slats.

Figure 2 shows schematically the star cutting process for producing the star or triangular lamellas that are used to produce the glued laminated timber according to the invention.

Figure 3 shows schematically a conventional

Glued laminated timber constructed from rectangular lamellas.

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Figure \ shows schematically the inventive, from

Glued laminated timber constructed from star or triangular lamellas.

Figure 5 shows schematically the manufacturing process of the glued laminated timber according to the invention.

The cutting process used to produce the triangular lamellae (Figure 2) differs from the conventional one (Figure \) in that no rectangular cross-sections are produced, but rather, after milling an octagon out of the round log, for example with the aid of a profile cutter, triangular lamellae 1 are cut with a so-called star cut (Figure 2). In this way, sixteen triangular lamellae 1 with a rectangular cross-section are produced, the long sides of which are 2/3 radial (Figures 2 and ⁵ O).

One advantage of this process is that no changes need to be made to the sawing machine, since the round wood used is always sawn at the same angle, regardless of its diameter. The lamellas produced then only differ in their width or height. In production, a system can therefore be used that, firstly, does not require complex control and, secondly, does not require any set-up times, apart from resharpening.

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of the saws, requires.

The second advantage of this process is the significantly higher yield of sawn timber. With the conventional sawing (Figure \), the yield of the main product is in the range of 45 - 50%, plus 10 - 15% of side products. With the star sawing (Figure 2), on the other hand, the yield is up to 73%; in addition, the sawn timber is completely available as the main product. The average yield with the star sawing process is therefore around 25% higher than with the conventional sawing.

Before the individual lamellas 1 are glued together, they must be dried and planed (Figure 5), which means a further loss of 30 - 35% for conventional lamellas, since the above-mentioned warping of the wood during drying means that the raw lamellas must be very large in order to obtain a full-sized lamella after the planing and planing process. These losses are reduced to 15 - 25%, or around half, for triangular lamellas due to the more favorable swelling/shrinkage behavior.

Overall, thanks to the star-cut process, the material losses from round timber to glued laminated timber will no longer be 60 - 70% as before, but only 40 - 60%. While a cubic meter of conventional finished lamellas costs between 600 and 650 DM, star lamellas can be produced for 400 to 450 DM, i.e. around 2/3 of the previous costs.

When producing the laminated timber according to the invention (Fig. 5), the cut triangular lamellae 1 are glued together after drying and planing. In this process, two of the triangular lamellae 1 are first joined together to form a cuboid 4 and glued together at an angle. Depending on the dimensions of the triangular lamellae 1 used, correspondingly dimensioned cuboids are obtained. The cuboids 4 are then glued together to form a beam of any length and/or width and/or height.

In a conventional rectangular slatted

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In the case of laminated timber (Fig. 3), the above-mentioned annual ring position is usually such that mainly horizontal annual rings are present, which means that, depending on the content of horizontal annual rings, the swelling/shrinkage behavior of the beam is unfavorable and the load-bearing capacity is limited.

In the star-cutting process used to produce the glued laminated timber according to the invention (Fig. 2), only lamellae 1 with vertical annual rings are necessarily produced. A beam composed of these triangular lamellae 1 (Fig. \) therefore has a much more favorable swelling/shrinkage behavior and, above all, is statically much more resilient than conventional glued laminated timber.

Claims (8)

Expectations 1. Glued laminated timber made of lamellae glued together, characterized in that triangular lamellae (1) made of radial cutouts from logs are glued together. 2. Glued laminated timber according to claim 1, characterized in that the cross section of the triangular lamellas (1) is designed as a right-angled triangle. 3. Glued laminated timber according to claim 2, characterized in that at least one of the two longitudinal sides (2 or 3) of the triangle is a radial. 4. Glued laminated timber according to claim 2, characterized in that both longitudinal sides (2 and 3) of the triangle are radial. 5. Glued laminated timber according to one of the preceding claims, characterized in that triangular lamellae of an octagonal section of a log are divided in the middle into two lamellae each (1). 6. Glued laminated timber according to one of the preceding claims, characterized in that two triangular lamellas (1) are joined to form cuboids (4) and glued together. 7. Glued laminated timber according to claim 6 in the form of a beam, characterized in that the cuboids (4) are glued together. 8. Glued laminated timber according to claim 7 in the form of a beam, characterized in that the cuboids (4) are glued to one another in such a way that the standing annual ring sections in the longitudinal section (Fig. \) of the beam extend substantially in the longitudinal direction of the beam.