EP1135565A1

EP1135565A1 - Wooden trussed structural systems, such as frameworks, bridges, floors

Info

Publication number: EP1135565A1
Application number: EP99950859A
Authority: EP
Inventors: Jean-Luc Sandoz
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-12-03
Filing date: 1999-10-28
Publication date: 2001-09-26
Anticipated expiration: 2019-10-28
Also published as: FR2786796A1; US20020124521A1; BR9915894A; EP1135565B1; FR2786796B1; JP2002531731A; WO2000032891A1; ATE248965T1; AU3791000A; DE69911055T2; DE69911055D1

Abstract

The invention concerns a wooden trussed structure wherein each beam (1)(2)(3)(4)(M) is constructed from at least three elementary planks (10,11, 12), nailed together, the plank (10) located in the central part being offset relatively to the ends of the lateral planks (11, 12), so as to form thereat, tenons and/or mortises (13) for inserting, at the junction forming a node, a panel-type reinforcement (15), positioned in the core, and whereof the shearing surfaces correspond to the lateral surfaces at each node, said panel consisting of a wooden structural element such as a micro-lath or plywood as a plate-type solid web.

Description

TRIANGULAR STRUCTURAL SYSTEMS IN BOTS. SUCH AS

FRAMES. BRIDGES. FLOORS

Technical field Wood is a material widely used in construction, and with which it is possible to produce a whole series of load-bearing systems having their own mechanical properties, and making it possible to support all levels and all types of loads.

The different wooden load-bearing systems are posts and beams, triangulated systems, articulated systems, gantries, beam grids, shells and elements functioning as plates.

Among all these structural systems, the triangulated system is the most universal, because it allows to take up very large loads, while being very simple to build. As an indication, the triangulated system is causing farm systems used in Europe and which have been developed since the ^12th century and are still used today.

The triangulated wooden systems are to be classified into two main families illustrated schematically in Figures 1 to 6 attached.

The first system, called “parallel frame system”, illustrated by FIGS. 1 to 3, is used for example for bridges or horizontal floor systems.

Such a system consists of:

- a die or upper chord (1),

- a lower die or frame (2), - posts (3) and possibly uprights (M),

- diagonals (4).

The assembly thus produced rests on at least two supports (5). To reduce internal stresses, it is sometimes possible to add supports inside the system, but this is not always possible. The “triangle-shaped” systems, as illustrated by FIGS. 4 to 6, are generally used to make the roof frames and make it possible to give the slope to the latter.

The elements involved in the realization of such systems consist of one or two rafters (6), a tie (7), diagonals (8) and possibly one or more uprights (9).

Such assemblies rest on supports (5) disposed at each end of the tie rod (7).

The invention relates to this technical sector and relates more particularly to the production of a new type of support system both with parallel members and in the shape of a triangle, which, while having high mechanical characteristics, make it possible to reduce the costs of production and is easily adaptable according to the characteristics desired for each particular application (load to be supported, dimensions of the system ...).

PRIOR ART One of the main problems which arise in the context of the production of both systems with parallel members and systems in the shape of a triangle, is that of being able to absorb the maximum force flow which is situated at the level of the supports and generates maximum tensions and compressions in the bars linked on the first node by the different elements which transmit the forces on the support.

Conventionally, the first node, in the case of frames, links, tie rods (7), crossbowmen (6) and diagonals (8), is made with solid wood or glued laminated wood pieces, according to the needs of section and the knot is made by means of metal fittings for systems with high inertia, or sometimes even simply glued for floor systems with lower inertia.

Numerous proposals have been made for the realization of the knot for assembling triangulated wooden systems, whether they are with parallel members or in the shape of a triangle. Among these solutions, mention may be made of that which is the subject of US Pat. No. 4,891

927 which proposes a reinforcement of the triangulation knot by an internal metal connector, provided with nails or pins which sink into the members made up of two layers. Such a solution is very expensive, because it requires a force and factory assembly of the knot, which eliminates the possibility of an artisanal assembly on the site itself, and which can be easily adapted according to the works to be carried out. Furthermore, it is not entirely satisfactory in that the strength of the knot is dependent on the section of the wood.

German patent DE 3 910 027 proposes a solution with two-layer dies and a triangulation system with plank or compound diagonals positioned in the core. However, such a solution does not make it possible to strengthen the most stressed nodes.

Furthermore, it has been proposed for a long time, as is apparent from US-A-2 886 857, in order to reduce the costs of manufacturing triangulated systems, to produce the beams used in the production of such systems, not to from solid wood of large section or relatively expensive glued wood, but by structures made up of boards nailed to each other to recompose larger sections from wood of small section, therefore economical.

Such a structure from nailed boards makes it possible to lower the cost prices and to recompose a large section without having the problems of solid wood such as deformations and cracks.

Furthermore, with thin planks, for example of the order of 30 to 50 mm, it is possible to carry out an artificial drying under conventional conditions.

In addition, the wood being nailed dry, there is no more deformation of the compound section.

The solution described in the aforementioned patent however has a certain number of drawbacks with regard to the strengthening of the nodes and is not adaptable equally to the two main families of triangulated wooden systems known as “parallel frame systems” and “triangle-shaped systems”.

First of all, this solution has boards in the central layer which are nailed between the two boards of the other members. This nailing tends to cause the central board to crack because the distance from the loaded edge, parallel to the fibers, is too small. This central plank core is therefore of poor performance in terms of its assembly.

Then, the fact of having a succession of planks in central core makes it possible to create inertia by spacing the external members, but this planked core being discontinuous transversely, it cannot take again neither the moment of bending nor the local shearing generated by the two internal beams, for example the compressed diagonal and the stretched upright. It therefore does not strengthen the knot in relation to bending and local shears which are important mechanical components of the knot system.

Finally, this central core is forced to fill all the space between the external members, since it only has rigidity on one axis, its longitudinal axis. This core therefore constitutes a global zone between the external members, and does not allow local reinforcement, adjusted for a single connecting node. It does not allow the optimization of the node, neither in performance (fragility in nailing), nor in economy of material (full area, compared to local area).

Statement of the invention

Now it has been found, and this is the subject of the present invention, that it was possible to produce structural systems both with parallel members and in the form of a triangle of the type illustrated by FIGS. 1 to 6 , the various elements of which - dies, diagonals, posts, tie rods, uprights, rafters, - which, in the following description, will be designated by the common expression "beam", allow, in a simple way, to reinforce the knots of junction between these elements, each beam being constructed from boards nailed to each other to compose larger sections. In general, in the wooden structural systems according to the invention, the different beams are produced on the site itself by nailing at least three elementary planks, nailed to each other, and they are characterized in that : - the three elementary boards constituting each beam are of the same thickness;

- the board located in the central part:

• being offset from the ends of the side planks, so as to form, at this level, tenons and / or mortises making it possible to include, at the junction zones forming a knot, a “panel” type reinforcement , positioned in the core, and whose shear surfaces correspond to the lateral surfaces at each node, said panel being constituted by a wooden structural element of the “microlame” or “plywood” type allowing the support area to be stiffened by functioning as a full "plate" type rib,

• consisting either of a continuous plank or of elementary planks placed end to end or spaced from each other so as to form a mortise capable of receiving a reinforcement of “panel” type or, possibly, for knots which would not require reinforcement, a simple tenon formed by the end of the central board of a beam associated with the system

Such a solution makes it possible to withstand greater efforts, the interface panels at the junction zones (node) increasing the nailing zones.

Furthermore, the solution according to the invention also makes it possible to reduce the bending moments in the joint since the reinforcement itself absorbs the bending since the “plate” type reinforcement has very high rigidity since it works in both directions of his plan. Such a reinforcement makes it possible to take up the shearing forces of the internal beams, such as for example the shearing between a compressed diagonal and a tensioned beam, at the level of the node, by mechanically relieving the external beam as much. This reinforcement can be more or less isotropic depending on the forces to be taken up.

As indicated above, the beams used in the production of a system according to the invention will consist of at least three layers, the reinforcements therefore being positioned at the level of the central layer, which allows double shearing of the through nails by compared to the reinforcement that would be exposed outside the system, as is often the case.

According to a particular embodiment which will emerge from the following description, in particular in the case of a system with parallel members, the two end posts will also consist of three layers nailed together, the central layer not being constituted by a board, but by a wooden structural element of microlame type extending beyond the ends of the two lateral boards as well as towards the inside of the structure in order to form tenons capable of receiving the mortises of the other beams of the system.

In addition to beams comprising three elementary layers, it can also be envisaged to produce beams with five or more layers, the reinforcement can either be positioned only in the central position, or can be doubled and then being positioned in the layers (two) and (four).

In other words, in such a case, the structural system according to the invention is characterized in that the number of planks entering into the constitution of each layer is odd and is greater than three, five for example, a reinforcement being positioned at each node in the even layers.

The ribs or reinforcing plates are arranged at least at the support zones where the forces are maximum. Possibly, the internal forces being lower in the uprights and diagonals, the assemblies of the triangulated system can possibly be carried out conventionally by a simple assembly of the “tenon / mortise” type, the tenon being formed by the offset towards the outside of the board. central, and the mortise by the spacing between two elementary planks constituting the central plank.

It is however advantageous to also reinforce these zones by fitting a reinforcing plate at this level making it possible to directly absorb the shear between the compressed diagonal and the tensioned post or vice versa. At the junction zones, the reinforcement or rib is fixed over its entire perimeter to the other beams (tie rods, crossbowmen, uprights or diagonals) by simple nailing, which is the most economical solution and which has the advantage of being semi- rigid allowing the entire plate to be stressed, after deformation of the edge connectors.

Brief description of the drawings

The invention and the advantages which it brings will however be better understood thanks to the following description which is illustrated by the appended diagrams in which:

- Figures 1 to 3 and 4 to 6 illustrate, as said above, the general structure on the one hand of the systems with parallel members and on the other hand in the form of a triangle achievable in accordance with the invention;

- Figure 7 is a schematic elevational view of a system with parallel members produced in accordance with the invention;

- Figure 8 is a detailed exploded perspective view of the circled area of Figure 7 showing the production of the assembly nodes at the support;

- Figure 9 is a schematic perspective view showing a frame produced according to the invention with nailing of the various elements together;

- Figure 10 is an exploded view, in perspective, of the realization of the nodes at the end support area and the central upright with the tie and the diagonal of the frame.

Way of realizing the invention

To produce these structures, the elementary planks used in the constitution of each beam are solid planks whose cross section is generally between 10 and 30 cm in width for 3 to 8 cm in thickness.

For structures that can represent a very high resistance, individual planks can be recomposed into larger sections.

The length of said boards can be variable and depends on the systems to be produced and will for example be between four to eight meters. The concrete examples of embodiment which follow will allow a better understanding of the invention.

Construction of a system with parallel members Such a system is of the type shown in FIG. 1.

To produce a system in accordance with the invention, illustrated by FIGS. 7 and 8, all of the beams entering into its constitution, namely the dies or members (1) and (2), the posts (3), diagonals ( 4) and the intermediate uprights (M) which the system comprises have the following structure.

Regarding the horizontal dies or members (1) and (2) as well as the diagonals (4) and the uprights (M) (uprights not shown in Figure 8), each beam consists of three elementary planks (10,11,12 ). The intermediate board (10) is offset with respect to the ends of the side boards (11,12), and this, in this case, by a distance of approximately 50 cm thus allowing to provide at each end a recess forming a mortise (13).

The diagonals (4) are produced in a similar manner from three boards and also have a mortise at their end.

The internal uprights (M) are made in a similar way.

The post (3) is, in turn, made up of two external planks (14) between which is inserted, over its entire length, a third plank (15), intended to constitute the panel-type reinforcement positioned in the core and which is formed of a microlame type structural panel having a thickness of 4 cm, the external boards (14) also having a thickness of 4 cm.

This panel (15) projects at each end with respect to the side boards (14,15) and forms a tenon having a height of 20 cm therefore corresponding to the width of the boards (10,11,12) constituting the dies, and a length 50 cm corresponding to the length of the mortise (13) provided at the ends of the beams constituting the dies.

The association of the different elements together is carried out by studding. If in the example illustrated, the reinforcement plate (15) extends over the entire surface of the system at each end at the level of the supports (5), it could possibly be envisaged to produce reinforcement plates only at each end , the central part of the post (3) then being constituted by an additional board, set back from the ends of the side boards.

Concerning the nodes (17) formed at the level of the internal junction zones, dies, uprights, diagonals, the connection is also carried out by inserting, at the level of the junction zones, additional plates.

Each of the elements therefore comprises at the junction zone a mortise intended to receive the reinforcing element.

Optionally, the assembly could be carried out without reinforcing element and the ends of the uprights (M) and diagonals (4) will have the shape of a tenon formed by the offset towards the outside of the central board while the dies or members (1,2) will include, along their length, mortises obtained by making the internal plank (10) by means of elementary planks spaced from each other by a length corresponding to the tenon of the ends.

Construction of a framework

Such an embodiment according to the invention is illustrated in FIGS. 9 and 10 and corresponds to the general structure which is the subject of FIG. 4, it being understood that structures of the type could be produced in a similar manner illustrated by figures 5 and 6.

This structure is also made from boards having a section of 20 cm x 4 cm.

In this example, all of the junction zones between the rafters (6), the tie rod (7), the diagonals (8) and the upright (9) have reinforcement panels designated by the same reference (20). As illustrated above, the set of beams used in the constitution of such a system, is made up of three elementary planks

(21,22,23) nailed to each other. The central plate (21) is, at the ends, set back relative to the ends of the side boards, so as to form at this level a mortise (24) capable of receiving a reinforcing element.

At the junction between the ends of the tie rod (7) and the crossbowman (6), the reinforcement insert (20) is of triangular shape, the base of which has a length of 700 mm and a height of 400 mm. .

At the knot formed by the diagonals (8), the uprights (9) and the tie (7), mortises are provided at each end of the diagonals (8) and uprights (9), and this by shifting the layer internal with respect to the ends of the side planks, the mortise in the tie rod (7) being, for its part, obtained by producing the central plank from elementary planks spaced from one another.

As before, the connection between the various constituents is obtained by nailing and the reinforcements (20) of the nodes, the junction of which is produced from a panel constituted by a wooden structural element of microlame type having a thickness of 4 cm.

Such systems with triangulated structure have many advantages compared to previous solutions, namely: possibility of realization on the same site, possibility of recomposing a large section, and this very economically, possibility of putting material (panel) , only to allow the necessary nailing and the resumption of the localized bending moment as well as the shearing of the internal beams arriving in the knot, for example the shearing generated by a compressed diagonal and a post stretched or vice versa.

Furthermore, the fact of making such a structure from nailed planks to constitute the different beams entering the system, makes it possible to make tenons and mortises by simply shifting one layer in relation to the others.

In addition, the reinforcement panels positioned in the core of each beam, make it possible to increase the surface of the nailing zones reinforcing the structure. Such an interface panel also regulates the bending moments in the articulation on the dies in the case of a system with parallel or triangulated members since the reinforcement itself absorbs bending; it thus absorbs the shear between the internal beams arriving in the node by mechanically relieving the external beam.

Of course, the invention is not limited to the embodiments described above, but it covers all the variants produced in the same spirit and can also be implemented to produce structures as shown diagrammatically in FIGS. 2, 3, 5 and 6.

Claims

1 / System with triangulated wooden structures, with parallel members or in the shape of a triangle, for the production of frames, bridges, floors, consisting of beams (1,2,3; 4, M) - (6,7,8, 9) constructed from at least three elementary boards (10,11,12,14,15) - (21,22,23), nailed to each other, characterized in that:

- the three elementary planks constituting each beam are of the same thickness;

- the board (10,15) - (21) located in the central part: • being offset from the ends of the side boards

(ll, 12.14) - (22.23), and this so as to form, at this level, tenons (16) and / or mortises (13-24) making it possible to include, at the level of the junction zones forming a knot, a reinforcement (15) (17) (20) of “panel” type, positioned in the core, and the shear surfaces of which correspond to the lateral surfaces at the level of each knot, said panel being constituted by an element structural wooden type

"Microlame" or "plywood" allowing the support area to be stiffened by functioning as a full rib of the "plate" type,

• consisting either of a continuous plank or of elementary planks placed end to end or spaced from each other so as to form a mortise capable of receiving a reinforcement of “panel” type or, possibly, for knots which would not require reinforcement, a simple tenon formed by the end of the central board of a beam associated with the system.

2 / structural system according to claim 1, characterized in that the number of boards entering into the constitution of each layer is odd and is greater than three, five for example, a reinforcement being positioned at each node in the even layers.

3 / Structural system according to one of claims 1 to 2, characterized in that the reinforcing plate constituted by a wooden structural panel constitutes the central board (15) of the beams constituting the posts (3) of a system with a triangulated structure with parallel members.