EP0034820B1 - Glued truss and formwork constructed therefrom - Google Patents

Description

The invention relates to a glued timber truss, which is particularly intended for formwork construction, and to a formwork formed using the same.

From DE-A No. 2006886 a carrier for construction purposes is known, the structure of which is outlined in the preamble of claim 1. This carrier has a one-piece upper chord and a parallel one-piece lower chord.

The upper and lower chords are connected to each other via diagonal bars and vertical posts, which are embedded in several parallel layers in the upper and lower chords with a rectangular cross-section and are connected by gluing. The shorter sides of the rectangular cross section from the upper and lower chord run parallel to the beam height. The diagonal bars and the vertical posts converge at their ends to form nodes in the upper and lower chord. The distance between knot points forms a compartment. Triangular compartments are formed in connection with the rising and falling diagonal bars. At predetermined points, the stiffening of the longitudinal member formed by the diagonal bars rising and falling is interrupted by sections which are delimited by vertical posts and are free of diagonal bars. In the area of these sections, the carrier can later be subdivided into individual carrier sections in such a way that end constructions are present at the ends of the carrier sections obtained in this way, forming the carrier end compartments in which the straps have an overhang. In order that the cross-section of the girder can absorb the same forces as the other girder cross-sections at undivided use, the vertical posts of these sections are expediently connected to each other for stiffening by a web plate or the vertical posts are arranged close to one another. The sections delimited by vertical posts and free of diagonal bars are only arranged in the longitudinal direction of the beam at those points at which later cutting to achieve a predetermined length of a beam section appears expedient, and these sections are less resilient in cross-section as a result of the interruption in the stiffening due to the absence of diagonal bars the other girder cross-sections if the vertical posts of these sections are not connected to one another by a web plate. If such a web plate is provided between the vertical posts in these sections, no cross member can be carried out when forming a formwork beam and if the space between the vertical posts of these sections arranged closely next to one another is not filled, then one has to be satisfied with small cross member heights, with which it is difficult to achieve the desired stability of the formwork girder when using long girders of this type arranged in parallel as longitudinal girders. In particular, it must be taken into account here that the non-filled area between the vertical posts of these sections, which are arranged closely next to one another, is unfavorable due to the lack of transverse stiffening to the belts for the introduction of forces transmitted via the cross members to the longitudinal members for reasons of the load-bearing capacity and bending rigidity. When creating formwork girders of high construction height with sufficient stability, it is therefore necessary to reinforce several parallel girders with cross girders that are attached to the lower flange so that the formwork girder has a total construction height that is equal to the sum of the construction heights of the longitudinal girder and cross girder is. When using such formwork beams as wall formwork, wide scaffolding platforms are required. If formwork anchors are attached, the girders must be drilled through the entire height to pass through the anchor, because the anchor plate for the formwork anchor can only be arranged on the lower chord side. All of this additional work is time consuming and cumbersome.

DE-A No. 2821907 describes a wooden girder construction in which the upper and lower chords are in two parts, so that the wooden girder construction has an open cross-section with three layers, the two outer layers consisting only of belts and the middle layer of diagonal bars is formed, the ends of which are glued together to form a knot with the two parts of the upper chord and lower chord using a plywood-based intermediate layer. The longer cross-sectional side of the upper and lower flange with a rectangular cross-section is aligned parallel to the beam height.

The rule for truss structures is to push the bars into the knots without eccentricity. In this way, additional stresses in the bars are avoided. If the bars are knocked off center in the truss, misalignment moments occur which result in additional stress. Therefore, the goal, in order to construct economically, is to keep the eccentricity - if not avoidable - as small as possible.

The invention aims to provide a glued timber truss girder which, while overcoming the difficulties and disadvantages of the prior art, has a uniform and sufficient bending stiffness and in particular has a compact design, is easy to manufacture and is suitable for formwork construction with other parts, such as cross members , can be connected using simple connecting means.

According to the invention, the disadvantages and difficulties in the prior art are remedied by the features specified in the claims. Appropriate further training are reproduced in the related claims.

According to the invention, the wooden truss has an open cross-section, which comprises at least three layers. Contrary to the otherwise usual principle in truss constructions, the filler rods in the invention are not brought together to form a node, but are at a predetermined distance from one another. The outer layers in the elevation level consist of belts, which are preferably divided into two, and vertical posts, which are divided into four and have a relatively large eccentricity to the imaginary junction. The middle, i.e. The position between the vertical posts, on the other hand, is formed only by a diagonal bar, which is arranged off-center both to the intersection of the bar axis belt posts and to the imaginary node to be set. The diagonal bars do not touch each other, but leave a space free. In the contact area with the two parts of the straps, they are glued flat. Since in the invention the longer sides of the rectangular cross section of the upper and lower chord run parallel to the beam height, there is a sufficiently large contact area between the diagonal bar and the upper and lower chord, so that a large glue area is available to simplify production. Belt weakenings are also avoided, which are unavoidable if the diagonal bars with the upper and lower belts have to be mortised and glued, so that a high degree of rigidity, in particular bending rigidity, is achieved.

To improve the bending stiffness, a diagonal bar is provided in each compartment, apart from possibly the end compartments, with a relatively large eccentricity in relation to the junction point that is intended to be applied, so that misalignment moments occur in the wooden truss beam according to the invention. These offset moments are accepted in the invention because a number of advantages are achieved thereby. Because the straps have rectangular cross-sections, the longer cross-section being parallel to the beam height, the additional moments resulting from the offset are absorbed.

The glued timber truss girder according to the invention is designed in such a way that, particularly due to its resolved cross-section, fastening means can be attached to almost any point on the upper and lower chord without having to drill. Holes weaken the belt. This advantage is particularly noticeable when formwork is attached to the formwork (can be supported on the top chord), several girders are assembled (girder joints can easily be realized on the protruding girdle ends in the area of the end compartments), supports are to be attached and suspension scaffold structures are to be attached. As a result of the use of thin wooden cross sections, the production is generally less expensive.

As is known per se, wooden construction parts across the grain are not very resilient. In claim 5 preferred designs of connections of the post with the straps are given. This improves the load-bearing capacity of the timber truss. This design of the connections given there enables the timber framework girder to be more resilient in the area of the vertical posts and, together with the measures according to claim 4, in the area of the ends of the timber framework girder, since the higher stress on the end timber can be used as a disc when designing the diagonal bar .

According to claims 6 and 7, a formwork, in particular large slab formwork, is formed using the timber truss girder according to the invention in that the spaces formed by the post expansion can be used to connect the crossbeams used in the spaces using, for example, squared timber. It can be seen from this that stable large-panel formwork with a high load-bearing capacity, which have a low overall height, can be assembled with the timber truss girder according to the invention. This not only improves the stability of the large panel formwork, it also saves space on the work platform of a wall formwork.

• Fig. 1 eine Seitenansicht eines geleimten Holzfachwerkträgers,
• Fig. 2 eine Schnittansicht längs der stufenförmig verlaufenden Schnittlinie 11-11 in Fig. 1,
• Fig. 3 eine Draufsicht auf eine Trägerstirnseite mit einem Trägerstoss,
• Fig. 4 eine Seitenansicht einer Verbindung von Querträger und Trägerenden,
• Fig. 5 eine Querschnittsansicht eines Grosstafelschalungselements mit mehreren geleimten Holzfachwerkträgern nach den Fig. 1 und 2 und Querträgern, und
• Fig. 6 eine vergrösserte Seitenansicht eines Endes eines geleimten Holzfachwerkträgers von Fig. 1 in einer bevorzugten Ausbildungsform einer Verbindung eines am Ende angeordneten senkrechten Pfostens zwischen den Gurten.

The invention is explained below using examples with reference to the accompanying drawings. It shows:

• 1 is a side view of a glued timber truss,
• 2 shows a sectional view along the step-shaped cutting line 11-11 in FIG. 1,
• 3 shows a plan view of a carrier end face with a carrier joint,
• 4 is a side view of a connection between cross member and carrier ends,
• 5 is a cross-sectional view of a large panel formwork element with several glued timber truss girders according to FIGS. 1 and 2 and cross beams, and
• Fig. 6 is an enlarged side view of one end of a glued timber truss girder of Fig. 1 in a preferred embodiment of a connection of a vertical post arranged at the end between the belts.

As can be seen from FIGS. 1 and 2, the wooden truss has upper and lower chords 1 and 2 with a rectangular cross section. The resolved cross section of the timber truss shown in FIG. 2 has three layers. The outer layers consist of belts 1 and 2 and vertical posts 3. The middle layer comprises only diagonal bars 4 arranged upwards and downwards between the belts 1 and 2 Posts 3 of two successive compartments r are at a distance a from one another, so that a square free space 5 is formed between the belts 1 and 2 by the expansion of the posts 3. All vertical posts 3 of the wooden truss are parallel arranges and glued in the belts 1 and 2 galvanized. Of course, other design forms of connections for the vertical posts 3 on the straps 1 and 2 are possible, for example using dowels.

The alternately rising and falling diagonal bars 4 do not meet at their ends, but are glued between the straps 1 and 2 in such a way that a free space 6 is formed in that the ends of the diagonal bars 4 are at a distance d from one another. In each compartment r of the timber truss, there are free spaces 5 and 6. The length of the wooden truss is an integral multiple of the compartment r. Therefore, the wooden truss can be cut to smaller lengths if necessary.

The upper and lower chords 1 and 2 are designed in two parts (see Fig. 2) and each part has a rectangular cross section. This rectangular cross-section is arranged in the timber frame girder in such a way that the longer cross-sectional side h in FIG. 2 runs parallel to the girder height. As a result, the straps 1 and 2 have sufficient flexural rigidity.

As can also be seen from FIG. 1, the wooden truss is designed such that the straps 1 and 2 protrude at its ends, namely by half the distance a between adjacent posts 3 of two successive compartments r. These protrusions facilitate the formation of a beam joint.

Since the wooden truss girder is expediently designed with at least three layers in accordance with FIG. 2, fastening means 13, 14 can be attached to almost any point on the upper and lower chord, which are used for connecting a formwork, for fastening formwork supports, for struts, Hanging frame or the like are determined. These fasteners 13, 14 can be easily carried out and attached by spreading the layers of the belts 1 and 2.

From Fig. 2 it can be seen that the cross sections of the straps 1, 2 are rectangular, i.e. that the ratio of the cross-sectional sides h to b is greater than 1. The diagonal bars 4 in the embodiment shown in FIG. 2 have the same width b as the belts 1 and 2 and the posts 3. If the resolved cross-section of the timber frame girder comprises more than three layers, the diagonal bars 4 are expediently wider than the belts 1 and 2. If, for example, crosswise arranged diagonal bars are provided, which is not shown in the drawing, a smaller width for the diagonal bars is also possible.

3 and 4, the formation of a beam joint is to be explained. For this purpose, two accessories 7 are arranged parallel to the top chords 1. In connection with a cross member 8 and using wedges 9, a circuit 10 can be attached without gradations. The wooden truss can therefore be extended in a very simple manner without the need for expensive bandages or special connecting means which have to be used in an otherwise conventional overlap joint.

5 shows, for example, a large panel formwork element which has a plurality of wooden truss girders as primary elements in accordance with the design according to FIG. 1. The same or similar parts as in Figs. 3 and 4 are given the same reference numerals in Fig. 5. For example, parallel squared timbers 7 and cross-distributing cross members 8 are shown. The crossbeams 8 extend through the free spaces 5 (FIG. 1) of the timber frame girder and in this way a stable flat girder with a reinforced top chord is formed for large-area formwork. The large-area formwork formed in this way has a low weight and a low static usable height, because the linings 11 are used to introduce the loads into the upper chords 1. Regardless of the use of large-area formwork as vertical wall formwork or horizontal ceiling formwork, such a compact construction with such a small height brings surprising advantages with large-panel formwork.

Finally, FIG. 6 shows an enlarged view of one end of a timber truss girder from FIG. 1. From this it can be seen that the upper and lower chords 1 and 2 protrude% a above the last vertical post 3. Also shown in Fig. 6 in broken line is a going through the belt 1 and glued into the post 3 round rod 12 through which the daytime forces are introduced into the post 3. Since the pressures that can be absorbed by the belts 1, 2 are only small across the fiber, round rods are expediently glued in, so that the bearing surface is kept small. High support forces can also be absorbed by gluing a pane of plywood, chipboard and / or metal plates in place of the diagonal bar 4 in the support area of the wooden truss girder. Of course, combinations of glued-in round bars 12 and designs of the diagonal bar 4 in the support area as a disk are also possible, wherein the vertical posts 3 can also be provided twice in this support area.

Claims (7)

1. Glued wooden truss, in particular for the construction of formwork, having parallel booms (1, 2), vertical posts (3) and diagonal web members (4), of rectangular cross-section, and comprising several boxes (r) in the longitudinal direction, that is to say there is a distance between the truss nodes, the booms in the truss end boxes having projecting ends, and sections, which are each bounded by vertical posts and are free of diagonal web members, being provided at certain points in the longitudinal direction of the trusses, characterised in that the exploded cross-section of the wooden truss comprises at least three layers, the two outer layers consisting of booms (1, 2), and vertical posts (3) of an exploded cross-section with a widening (a), that is to say there are two consecutive boxes (r) at a distance between adjacent vertical posts (3), the truss nodes each having to be placed, in an imaginary view in the longitudinal direction of the trusses, in the middle of the widening (a) in the upper or lower boom (1, 2), that, moreover, in all boxes (5) with the possible exception of the end boxes, the central layer between vertical posts (3) is formed only by diagonal web members (4) which, in the region of the booms (1, 2), are glued in with their surfaces between the boom parts and have a mutual distance (d) which is smaller than the widening (a), that the longer cross-sectional sides (h) of the rectangular cross-section of the booms (1, 2) are parallel to the truss height, that each box (r), with the possible exception of the end boxes, comprises only one diagonal web member (4), as viewed in the longitudinal direction, and that the boxes (r) are all made with the same length.

2. Wooden truss according to claim 1, characterised in that the exploded cross-section of the wooden truss comprises five layers, three layers consisting of booms and vertical posts, between each of which a layer is arranged which is formed only by diagonal web members (4).

3. Wooden truss according to claim 1, characterised in that the booms (1, 2), the posts (3) and the diagonal web members (4) have identical cross-sections.

4. Wooden truss according to one of claims 1 to 3, characterised in that the diagonal web members (4) of the end boxes are shaped as a disc which has a multi-layer structure consisting of plywood, chipboard and/or metal panels.

5. Wooden truss according to one of claims 1 to 4, characterised in that the posts (3) are joined to the booms (1, 2) by means of dovetailed glued bonds and/or by means of glued-in round bars (12) of hardwood, ground steel or the like, which pass through the booms (1,2) and project into the end grain of the posts (3) flush with the surface, or that the posts (3) are joined to the booms (1,2) by glued-in self-tapping cylindrical screws.

6. Formwork constructed with the use of a truss according to one of the preceding claims, characterised in that several trusses are arranged parallel and the upper boom is reinforced by a panel, and cross girders (8) pass through the free spaces (5) formed by the widening (a) in the particular truss.

7. Formwork according to claim 6, characterised in that, in place of every second and third truss arranged in parallel, a square timber (7) resting on the cross girders (8) is provided.

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