FR2669066A1 - Device for stressing glued laminated wood beams - has two curved half-beams on adjustable platform to cater for two or more supports using chamber - Google Patents

Abstract

Equipment for stressing glued laminated wood beams on two or more supports, comprises two curved half-beams (1,2) on an adjustable platform. The radius of curvature is a function of the prestressing force. For two supports, the platform is cambered equal to the beams' camber plus a stripping relaxation allowance. For more supports platform and half-beams are alternately cambered and deformed. The half-beams' cambers are added to the platform's to impart the prestressing value to the beam. Curvature imparted to the half-beams plus camber less relaxation equals prestressing camber. USE/ADVANTAGE - Balanced prestressing without cables anchors etc.

Description

DESCRIPTION
PRECON GLUE LAMELLED WOOD BEAMS
BALANCED TRAIN
the present invention concerned the manner. to obtain, only by deformation, a balanced equal prestress at the top and bottom of the section (compression compression).

 It is in the field of glued laminated wood structures for more specifically its application to isostatic and hyperstatic beams.

 Traditionally, prestressing on glued laminated wood beams is for example carried out using steel wires stretched in housings of generally parabolic shape; they are stopped at their ends by anchor cones supported on metal shoes. The system, with non-adherent wires, has similarities with the technique used for concrete.

The difference lies in the possibility for the wood to envisage a state of equal stress in tension and compression. Unfortunately the position of the wires, their eccentricity does not allow this equality to be obtained.

The implementation of the process:
- shaping of the wire housing,
- installation of support plates and anchor cones,
difficult application to a hyperstatic structure, in fact a heavy system to which is added the problem of protection of hypertensive wires.

 The process which is the subject of the invention makes it possible to remedy these drawbacks; it does not use any other means than the glue and wood usually used for the manufacture of closed beams on glued laminated wood.

 [, with distribution of the stresses is the same one on the lower and higher ribs, the prestressing is balanced.

 according to the invention, it comprises a first characteristic: two pre-curved half-beams of a value related to the prestressing force to be obtained are presented after gluing of the assembly joint, arrows at the top, shaped and held tight by stirrups on a convex shaping bench adjusted according to the profile to be produced.

 After polymerization of the adhesive joint and stabilization the beam is ready for use.

 The clamping on the form gives the two half-beams the prestressing force: the upper fiber is stretched, the lower is compressed.

 When loading the resulting beam, the forces will reverse, compression at the top of the section, traction at the bottom.

 The value of the prestress is a function of the curvature of the half-beams, of the amplitude of the convex part of the form, of the relaxation on demolding.

Finally:
(the curvature of the half-beams) + (the arrow on the shape) - relaxation = the prestressing force
The accompanying drawings illustrate the invention.

 - Plate 1 in figure 1 represents the diagram of a beam on two supports.

 - Figure 2 plate 1 represents the initial position of shaping of the elements.

 - Figure 3 the half-beams clamped on the form bench.

 - Figure 4 the resulting beam installed, after demolding, on two supports.

 With reference to these drawings, the device comprises: FIG. 2 two half-beams (1) and (2) presented arrow up (4) on a bench (3) of convex shape (5).

 Figure 3 shows mark (6) the resulting beam assembled by the adhesive joint (8) held on the bench (3) by stirrups (7).

Figure (4) shows mark (6) the beam
@@ llante with two supports with its manufacturing arrow
cation (9).

 plancîto 2 schematically represents figure 5 the curve of the moments of a beam on multiple supports.

 Figure 6 the initial position of shaping of the elements on multiple supports.

 Figure 7 the half-beams of alternate curvature flanged on the form bench.

 Figure 8 the resulting continuous beam after demolding.

 The device comprises FIG. 6 two half-beams (10) and (11) of alternating curvatures according to their position in span or on supports (13) and (14). (15) and (16) represent the concave and convex parts of the form bench (12).

 Figure 7 shows mark (17) the resulting beam assembled by the adhesive joint (18) held on the bench of alternately convex and concave shape by stirrups (7).

 Figure 8 plate 2 shows mark (17) the resulting beam assembled by the adhesive joint (18).

 The reference (21) represents a load installed in span on the convex part.

 The mark (22) a load on the cantilever joint.

 (19) and (20) the location of the supports.

 Plate 3 in FIG. 9 represents the diagrams of the different charge states obtained in application of the invention.

 The (23) is the diagram as there is figure 3 board 1 and figure 7 board 2.

 The reference (24) represents the value of the relaxation generated by the mold release.

 The reference (25) is the result of the transformation of the diagram (23) due to the relaxation (24).

 The reference (26) represents the diagram resulting from a stress which would have for value the maximum bearable by a normal beam not prestressed.

 The reference (27) represents the diagram resulting from a new constraint equal in value to the previous case.

 To read the different diagrams, the parts to the left of the vertical bars show the tensile stresses, the parts to the right the compression stresses.

 The method, object of the invention, is particularly intended for the improvement of glued laminated wood structures.

Claims (2)

 1 Device for the constraint of beams in i is glued lamella, on two supports and more, characterized ('10 ('O that it comprises two-half curved beams (1) and (2) or (10) (11 ) assembled by gluing on a previously adjusted form bench.  3) Device according to claim 1 characterized in that the form bench has a convex part (for beams on two supports) of a value equal to the manufacturing arrows plus that of instantaneous relaxation on demolding.  2) Device according to claim 1 characterized by the prior shaping of two curved half-beams, the value of the radius of curvature (4) or (13) and (14) is a function of the prestressing force to be obtained within the limit characteristics of the material  4) Device according to claim 1 characterized in that the form bench and the half-beams alternately have convex and concave parts (15) and (16) for application on multiple supports.  5) Device according to claim 1 characterized by the absence of other means for obtaining the result than that of the assembly by gluing of the two curved half-beams (1) (2) or (10) (11) on the forming bench (3) or (12).  6) Device according to the preceding claims taken as a whole characterized by the fact that the arrows of the curved half-pieces (4) or (13) are added to those of the form bench (3) or (12) for printing on the resulting beam the value of the prestress.  7) Device according to the preceding claims, taken as a whole, characterized in that: the value of the curvature previously imprinted on the half-beams plus the value of the arrow obtained when tightening on the bench less the relaxation at the exit of the bench equal the value of the prestressing deflection.