GB2051908A

GB2051908A - Prefabricated Roof Truss

Info

Publication number: GB2051908A
Application number: GB7920513A
Authority: GB
Original assignee: Jean Champeau Et Cie SA Entrep
Current assignee: Jean Champeau Et Cie SA Entrep
Priority date: 1979-06-13
Filing date: 1979-06-13
Publication date: 1981-01-21

Abstract

A prefabricated roof truss has a lower tie-beam (8) fixed between principal rafters (1, 2). Uprights (9, 10) extend between the tie-beam (8) and the rafters (1, 2) and delimit the habitable area of the roof. A joist (14) is spaced apart from the tie-beam (8) and fixed to the uprights (9, 10). The joist (14) is rigidly connected to the tie-beam (8) to form a beam (16) which is capable of supporting a floor. <IMAGE>

Description

SPECIFICATION A Prefabricated Truss The present invention relates to a prefabricated truss.

The industrialisation of building has been accompanied by the appearance of prefabricated trusses on the market. Such trusses have been described, for example, in published French Patent Applications No. 2,303,911 and No.

2,305,561.

Furthermore, it has already been proposed to incorporate a joist in a truss in order to render a roof habitable. A construction of this kind has been described in published French Patent Application No. 2,197,103. However, because of the mass of the truss produced for this purpose and because of the floor stress, a construction of this kind can only be achieved by the prefabrication of three elements, delivered separately to the site, on condition that an intermediate support is provided for the beam assembled on the site.

It is an object of the invention to provide an entirely prefabricated truss incorporating a joist which is capable of supporting a floor in the absence of any intermediate support.

According to the present invention there is provided a prefabricated truss comprising a lower tie-beam and first and second members extending upwardly from the tie-beam and delimiting a roof space, a joist being mounted in spaced apart relationship relative to said tie-beam and being rigidly assembled thereto to form a beam, the joist being fixed at each of its ends to a respective one of said upwardly extending members.

The beam, which is capable of supporting a floor, may be a lattice beam. The lattice beam is assembled by any suitable technique, for example by the technique of forming mixed wooden/metal beams, as described in French Patent 1,542,293.

In an embodiment, the beam formed by the rigid assembly of the tie-beam and the joist is a compound beam, for example a plate-web beam.

In all cases, according to the invention, the joist and the tie-beam are spaced apart from one another. This construction provides the truss with a better resistance to deformation as the tie-beam and the joist have separate points of attachment to the other elements of the truss, and as the joist and the tie-beam are rigidly joined together. At the same time, the structure is very much lighter than structures in which the functions of the tiebeam and joists are performed by a single massive beam. As the structure is light it is not necessary to provide intermediate support points.

One end of the joist is preferably attached to a first upright extending between the tie-beam and a first principal rafter. The other end of the joist is attached either to a second opposite upright or to the purlin post of the opposite principal rafter and/or to the opposite principal rafter.

Embodiments of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a plan view of a first embodiment of a truss according to the invention, Figure 2 shows a plan view of a second embodiment of a truss with another type of beam, and Figure 3 shows an end view of the beam employed in the embodiment of Figure 2.

The wooden prefrabricated truss shown in Figure 1 comprises two principal rafters, 1 and 2, an upper double tie-beam, 3 and 4, and a kingpost 5, to which no further reference will be made because it forms part of the known art. As is known, each of the principal rafters, 1 and 2, is assembled in the workshop from two pieces by means of a respective brace, 6 or 7, and bolts at the level of attachment of the rafters to the upper double tie-beam 3 and 4.

A lower tie-beam 8 is joined, by each of its ends, to the base of the two principle rafters 1 and 2. The truss additionally comprises two uprights, 9 and 10, and also two purlin-posts, 11 and 12. Everything which has been described hitherto forms part of the art. All the pieces described can be assembled by any suitable means, such as clamping by means of metal connectors 13 as described in French Patent 1,474,407.

According to the invention, the truss additionally comprises a joist 14 which is mounted so as to be spaced from the tie-beam 8.

This joist 14 does not extend over the same length as the tie-beam 8, but only over the length between the uprights 9 and 10, to which its ends are fixed by means of metal connectors 1 5.

The joist 14 and the tie-beam 8 are rigidly joined in order to form a lattice beam denoted by 1 6. This lattice beam 1 6 comprises connecting supports 1 7 and stays 18. In one embodiment, the connecting supports 17 are made of wood and are fixed to the joist 14 and to the tie-beam 8 by means of metal stays 18, the ends of which are shaped as metal clamping connectors.

A truss such as that described is very simple to manufacture. Of course, the lattice beam 1 6 will be prepared as a single unit before the other pieces are assembled.

This truss is also relatively light in terms of the acceptable floor stress. It is easy to position without intermediate support, on two opposite walls 19 and 20.

Figure 2 shows a further embodiment which is suitable for a roof possesing a sitting dog. In order to simplify the description, the features of Figure 2 which are the same as features described with respect to Figure 1 are not further described.

In the embodiment of Figure 2, the purlin-post 11 acts as the upright on one side, that is, on the left-hand side as shown in Figure 2. Thus, the joist 1 4 extends as far as the purlin-post 11 , that is to say substantially onto the principal rafter near the foot of the truss. This is the point which, in order to simplify the description, is referred to above as the foot of the truss. A single, metal clamping connector 21 can, if necessary, join the principal rafter 1, the purlin-post 11 and the joist 14.

In another modification, which is not related to the above described modification, the beam 16 is not made into a lattice beam but into a compound plateweb beam. That is to say, the beam 16 comprises two half tie-beams, 8 and 8', separated in the longitudinal direction, and two half-joists, 14 and 14' separated in the longitudinal direction, the whole being joined by a laminated web 27 as is shown in Figure 3.

Claims

1. A prefabricated truss comprising a lower tiebeam and first and second members extending upwardly from the tie-beam and delimiting a roof space, a joist being mounted in spaced apart relationship relative to said tie-beam and being rigidly assembled thereto to form a beam, the joist being fixed at each of its ends to a respective one of said upwardly extending members.

2. A truss as claimed in claim 1, wherein the beam formed by the rigid assembly of the tiebeam and the joist is a lattice beam.

3. A truss as claimed in claim 2, wherein said lattice beam is a mixed wooden/metal beam.

4. A truss as claimed in claim 1, wherein the beam formed by the rigid assembly of the tiebeam and the joist is a compound beam.

5. A truss as claimed in claim 4, wherein said compound beam has a solid web.

6. A truss as claimed in any preceding claim, wherein said first upwardly extending member in a first upright extending between the tie-beam and a first principal rafter.

7. A truss as claimed in claim 6, wherein said second upwardly extending member is a second upright arranged opposite to said first member and extending between the tie-beam and a second principal rafter.

8. A truss as claimed in claim 6, wherein the second upwardly extending member is a purlinpost attached to a second principal rafter and/or the second principal rafter.

9. A prefabricated truss substantiaily as hereinbefore described with reference to and as illustrated in Figure 1, Figure 2 or Figure 3 of the accompanying drawings.