FR2519671A1 - SKATE WOOD BEAMS - Google Patents

Abstract

Glued wooden beams intended particularly to concrete formwork in building and civil engineering. The cross-section of the beam has the shape of a rail and comprises a massive top boom (1) and a large bottom boom or footing block having a lower mean thickness (2). The single or double web (3) is comprised of plywood of which both thread directions of the plies are at 45<o> with respect to the booms. In the case of a double web, the two planks may be parallel or converging upwardly, the interval being either empty or filled with expanded synthetic material.

Description

SKATE WOOD BEAMS
The present invention relates to composite beams of glued wood intended in particular for concrete shuttering on construction sites: residential, public or industrial buildings, engineering or civil engineering structures.

The beams of this type already known often replace squared timber (baslaings or planks) thanks to their significant weight gain equal strength and their longevity.

They are mainly used in two ways - Horizontally and supported by props, they constitute a temporary joist supporting the formwork which receives the concrete from the floors (fig. 1).

- Vertically, they serve as stiffeners for the opposite formwork receiving the concrete from the walls (fig. 2).

The various existing beams are reduced to two types (fig. 3) - A truss where the members are joined by struts.

- Solid web, I-section where the frames are joined by a massive web or 9 three layers.

The various elements are assembled by finger jointing and gluing.

In all cases, the cross section of the beam is symmetrical with respect to a horizontal axis, the two members are identical, massive and rectangular.

The slenderness of the section (ratio of the height to the width) varies from 2.5 for the lightest joists to 3.6 for the tallest.

This type of section has the following main drawbacks - In horizontal use, there is a significant risk of overturning when workers pass by with them falling, due to the fault width of the beam, the actual width of the beam. support being further reduced by the chamfer of the frames.

Difficulty in nailing the joist to its support due to the massive shape of the support member.

- In vertical use, small support width for the formwork subjected to the very strong pressure of the concrete when the walls are being poured.

- For solid core beams, limited resistance to shearing forces due to the low resistance of the wood to shear forces parallel or perpendicular to the fibers.

- For truss joists, very unequal resistance to shearing forces depending on whether the support of the joist occurs at a truss knot or between two knots.

The beams according to the invention make it possible to avoid these drawbacks.

They have a continuous, solid or boxed core. The cross section has two members of different sections (fig. 4)
An upper chord of rectangular section or close to the rectangle (1)
A lower chord or shoe, wider and of lower average thickness (2).

The two members have an equivalent inertia with respect to an axis located at mid-height of the section.

Each member can be solid, made by gluing or glued board.

The profile of the joists is reminiscent of that of a classic sliding rail.

In horizontal use, the beam resting on its shoe is perfectly stable to the passage of workers walking on the narrow upper chords.

In addition, it is easy to nail the joist to its support.

In vertical use, the shuttering skin is nailed to the shoe which, due to its width, significantly reduces the free span of the shuttering panels, which makes it possible to further space the joists arranged as vertical stiffeners.

The & e of the beams (3) according to the invention consists of one or two plywood boards according to the possible arrangements indicated (fig 4).

The peculiarity consists in arranging the wires of the plies of the counterplate that å 450 in relation to the frames, which, at equal thickness, significantly increases the resistance to shearing.

côtes en cm.The beams according to the invention 'can be made in different substantially homothetic sections, with a height varying for example from 20 to 40 cms, non-limiting dimensions, the profile being characterized by the relationship between the height of the section H and the widths of the members. , upper b and lower (or pad) B;

ribs in cm.

Figure b shows an embodiment of a beam 22.5 cm high, comprising a plywood core 15 m / m thick and widths b - 8.5 cm and B - 11.5 cm.

Claims (3)

- CLAIMS easy nailing of the joist on its support. - In horizontal use ensure excellent stability and height of the section, said asymmetry allowing brures being of a substantially equivalent inertia with respect to the mid is wider and less thick than the upper chord the two members revised by their asymmetry due to the fact that the bottom chord or shoe Beams made of glued timber with I-carac cross section formwork between stiffeners trace to the width of the shoe. - When using vertical stiffeners, reduce the free door of 2 beams made of glued wood, according to claim 1, of which the single or double core is made of plywood, the wires of which folds are inclined 45th with respect to the chords. 3 beams made of glued timber according to claims 1 and 2, of which the box core may have two parallel plywood boards or converging upwards, the space between the two boards being either vacuum is filled with expanded synthetic material of density fault.