EP2071095B1 - Beam comprising a light weight concrete boom and a partially embedded truss in this boom - Google Patents

Description

The invention relates to a beam for use in the construction of a building.

BACKGROUND OF THE INVENTION

Such a known beam comprises a metal mesh forming a core, which is rigidly secured to a concrete heel, of generally parallelepiped shape. The wire mesh is a structure formed by steel bars, which is secured to the heel having its lower part embedded in this heel.

Such beams which are generally prefabricated are used for the realization of floors of single-family houses, group houses or buildings, either under construction or renovation.

Several beams are then placed parallel to each other being regularly spaced from each other, each beam having its heel located at the bottom, each lattice protruding from an upper face of the heel which it is secured.

Interjoists are then placed between two neighboring beams, so as to close the spaces between them. On this structure, a reinforcing reinforcement is put in place, and poured over the concrete forming the compression slab, so as to completely cover the trellis, to form the floor.

In this context, the known beams have satisfactory mechanical characteristics, but they have a significant weight which limits their use.

For example, on a renovation site of a building, access is difficult and it is generally not possible to provide a hoist for handling the beams. These must then be carried and set up manually by operators under conditions of great difficulty.

Concretely, the known concrete heel beams 4 cm thick have a weight of about 14 to 15 kg per meter, whereas it is considered that to be easily handled manually, a beam must have a weight of the order of 8 kg per meter. Indeed, a beam with a range of 6 meters and weighs about 50 kg and can be handled by two people.

To obtain a lighter structure, it was designed beams of similar morphology, but having a heel made of wood instead of being poured concrete, the mesh then being stapled or nailed to the wooden heel.

However, wood is a putrescible material, its use is prohibited for a crawl space, especially because of its sensitivity to termites, so this solution is not completely satisfactory.

In addition, in the case of wood, the craftsmen consider that it does not behave in a sufficiently stable manner for this type of application. He finally asks for an important shoring. The document FR2540540 discloses a beam having a concrete heel which is surrounded by a polystyrene shell having the function of increasing the thermal resistance of the beam. It is still known from the document FR2862994 a beam comprising a lattice, a U-shaped rail-shaped reinforcing metal sole, and a heel cast in this sole to coat part of the lattice, this heel being formed of light insulator such as a polyurethane foam.

This solution makes it possible to manufacture beams light enough to be handled manually. However, this solution is unsatisfactory in terms of fire resistance, so that the manufacture of a floor with such beams requires adding a reported protective ceiling.

This reported ceiling may be formed of a gypsum plaster of 2 cm thick, or gypsum board specifically designed to isolate fire, which induces a significant additional manufacturing cost.

Thus, both the wooden heel solution and the foam heel solution have drawbacks that greatly limit their use.

In other words, the known lightweight beams are not sufficient to equal the solution mesh and concrete heel with respect to all the performance that is expected of these beams, such as stability over time, fire resistance, and the cost of manufacture.

Similarly, recent lightweight concrete materials are also not suitable because they have a too low durability, so that they degrade thereby causing a degradation of the trellis, and therefore the entire beam.

OBJECT OF THE INVENTION

The object of the invention is to propose a solution to overcome the above disadvantages.

SUMMARY OF THE INVENTION

For this purpose, the subject of the invention is a beam comprising a heel and a lattice rigidly integral with each other and extending in a longitudinal direction, the lattice being an arrangement of steel bars welded to each other. others which is partially embedded in the heel to secure it to this heel while partially protruding from a so-called upper face of the heel, characterized in that the heel is lightweight concrete and that it comprises a polypropylene shell or polychloride vinyl, this shell covering and adhering to at least one of the faces of the heel.

With this solution, the material of the heel is protected from external aggressions by the shell, which improves its longevity. The heel is cast in a material such as lightweight concrete, without the risk of degradation.

The invention also relates to a beam as defined above, in which each end of the shell surrounds one end of the trellis, and in which each end of the trellis is suspended at one end of the shell.

During the manufacture of the beam, the mesh is put into position by simply engaging each of its ends in a corresponding end of the shell to hang it. The concrete of the heel can then be cast without having to wedge the trellis relative to the bottom of the hull.

The invention also relates to a beam as defined above, in which the shell comprises a sole in the form of a plastic profile having a cross section having a generally U-shaped shape, as well as two end-pieces each nested at one end of the soleplate. so as to form a mold for casting the concrete of the heel.

The invention also relates to a beam as defined above, in which the shell also comprises a hood which cap the soleplate by fitting on it, and in which each end of the cap surrounds one end of the trellis while being provided with lattice holding means suspended from this hood.

The invention also relates to a beam as defined above, in which each end of the cover is in the form of an easel, and in which the means for holding the suspended trellis are lugs projecting from the internal faces of this trestle.

The invention also relates to a beam as defined above, wherein the trellis comprises three straight bars extending parallel to the heel, including two so-called lower bars embedded in the heel, and a so-called upper bar by which this lattice is suspended from the hull.

The invention also relates to a beam as defined above, comprising means for holding the mesh suspended from the shell located between the ends of the mesh and the shell.

BRIEF DESCRIPTION OF THE FIGURES

• the figure 1 is a perspective view showing the lattice and the sole of the beam according to the invention;
• the figure 2 is a perspective view showing the lattice with the sole and the cover of the beam according to the invention;
• the figure 3 is a perspective view showing the beam according to the invention as a whole;
• the figure 4 is a perspective view showing a variant of beam according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The beam according to the invention 1, represented in figure 1 , comprises a lattice 2 formed of metal bars partially embedded in a concrete heel not visible in the figure 1 , the lattice and the heel extending in a direction AL corresponding to the main direction of the beam.

The heel is cast in a sole or plastic chute, marked by 3 in the figure 1 and also extending parallel to the AL direction.

The lattice comprises three straight steel bars 4, 6 and 7, parallel to the direction AL being located at the vertices of an isosceles triangle when viewed in cross-section with respect to the axis AL.

The bar 4 is a so-called upper bar, which is located outside the concrete heel, and bars 6 and 7, said lower, are located in the sole 3 being completely embedded by the concrete of the heel.

These straight bars are connected to each other by U-shaped or V-shaped steel bars, indicated by 8 and 9, each bent bar being welded to each of the three straight bars.

The bent bars are arranged along the straight bars being regularly spaced from each other, the straight bars being located on the inner side of the V formed by each bar bent.

Each bent bar has a shape of U or V comprising two branches joined by a base area with strong curvature, each branch thus having a free end opposite to the base area.

Each bent bar has its base area welded to the upper straight bar 4, and each of its branches welded respectively to the lower straight bar 6 and 7.

The bent bars 8 and 9 which have flat shapes are oriented in planes oblique to a plane normal to the longitudinal direction AL, being inclined by about thirty degrees with respect to the latter. The inclinations of the bent bars are alternated: two consecutive bent bars 8 and 9 along the straight bars have opposite inclinations with respect to a transverse plane.

The ends of the branches of the bent bars 8 and 9 constitute, together with the lower straight bars 6 and 7, two straight lower edges of the mesh, which are completely embedded in the concrete of the heel, once it is cast.

The sole 3 is a plastic profile, obtained for example by extrusion, having a general shape of chute or rail. Its cross section has a generally U-shaped, the ends of the branches of this U being folded inwards.

This sole 3 thus comprises a main wall, namely a bottom wall 11 corresponding to the base of the U, extended by two side walls 12 and 13 each corresponding to a branch of the U. These walls are generally flat, two adjacent walls being perpendicular. one to the other.

Each side wall is itself extended by an upper wall, or return, marked respectively by 14 and 16, these returns being flat walls in the form of strips parallel to the bottom wall.

These returns have their free edges located vis-à-vis one another while being spaced from each other by a distance corresponding to the width of the lattice to define an opening traversed by the trellis which thus exceeds the sole.

This sole has a symmetrical shape with respect to a plane containing the longitudinal direction AL and normal to the bottom wall 11.

It defines a generally parallelepipedal internal space delimiting the shape of the concrete heel, having a lower face corresponding to the wall 11, two lateral faces respectively corresponding to the side walls 12 and 13 and an upper face located at the level of the return walls 14 and 16 .

The lower walls 11 and side walls 12 and 13 are generally flat while being provided with ribs oriented in the direction AL, marked by 17, which give relief to the internal faces of these walls, so as to obtain the best possible cohesion between the soleplate 3 and concrete heel poured into it.

The beam also includes a hood 18, appearing in the figure 2 , and which fits on the sole 3 partially covering the trellis and the upper opening of the sole.

Just like the sole 3, the hood has a symmetrical shape with respect to a vertical median plane of the beam. It comprises two lateral parts 19 and 21 symmetrical to each other with respect to the median plane, and connected to one another by two bridges in the form of arched walls 22 and 23 covering the trellis and located at the ends of the parts 19 and 21 along the AL axis.

The first lateral portion 19 comprises an upper wall 24 having an outer longitudinal edge extended by a side wall 26 oriented perpendicularly to this upper wall, and an inner longitudinal edge extended by a medial wall 27. The second lateral portion 21 similarly comprises a upper wall 28, a side wall 29, and a medial wall 31.

The upper walls and the side walls have longitudinally extending rectangular strip shapes, the two upper walls being located in the same plane, and the side walls extending parallel to each other.

The hood 18 fits on the upper part of the sole, so that once in position, as in the figure 2 or 3 , its upper walls 24 and 28 respectively cover the returns 16 and 14 of the sole, and its opposite side walls 26 and 29 partially cover the opposite side walls 12 and 13 of the sole.

The interlocking of the cover 18 on the upper part of the soleplate is ensured by two longitudinal ribs 32 and 33 protruding from the outer faces of the walls 12 and 13 of the soleplate, and which fit respectively into two longitudinal grooves 34 and 36 , complementary, made at the inner faces of the side walls 26 and 29 of the cover.

The hood is also provided with longitudinal ribs 37, 38 protruding from the lower faces of its upper walls 24 and 29, and which bear on the inner edges of the returns 12 and 13 of the sole, the upper walls 24 and 29 having more large dimensions that these returns, to cover them completely.

The assembly formed by the rib 32 and the complementary groove 34 in combination with the longitudinal rib 37 provides a snap of the side portion 21 of the hood on the sole. Similarly, the assembly formed by the rib 33 and the groove 36, with the rib 38 ensures the latching of the side portion 19 on the sole.

Each arched wall or bridge 22, 23 has a shape that is symmetrical with respect to a longitudinal median plane, and these walls 22 and 23 are symmetrical to one another with respect to a plane normal to the longitudinal direction AL.

The arched wall 22 comprises a curved portion 39, in the form of a cylinder portion of axis coinciding with the upper bar 4, extended by two flanks 41, 42 connecting this curved portion respectively to the side wall 27 and the side wall 31.

The vaulted portion 39 thus surrounds one end of the upper straight bar 4, and constitutes, because it is formed of plastic material, a pseudo joint allowing the side parts 19 and 21 to be moved apart or brought closer together. the other. But the mesh 2 is suspended from this arched wall, being supported on four pins protruding from the inner faces of the flanks 41 and 42 of this arched wall.

More particularly, the flank 41 comprises two lugs 43 and 44, in the form of walls with a generally triangular outline, protruding from the internal face of the sidewall. 41, being located near the curved portion 39 and extending in a plane normal to the longitudinal direction AL. The other side 42 also includes two lugs protruding from its inner face, one of which, marked 46 is visible in the figure 2 .

The other arched wall, namely the wall 23 also includes a curved cylindrical portion 47 extended by two flanks 48 and 49 connecting it to the median walls 27 and 31 of the cover 18. It is also provided with four lugs suspension bar rectilinear upper 4, in accordance with the provision of the arched wall 22.

As shown in the figures, the side wall 27, and the flanks 42 and 49 form a single generally flat wall inclined at about thirty degrees to a longitudinal median plane normal to the bottom wall of the sole. Similarly, the side wall 31 and the flanks 41 and 48 also constitute the same plane wall inclined at thirty degrees with respect to the median plane.

As shown in the figure, the mesh 2 is suspended from the trestles formed by the arched walls 22 and 23, each end of its upper straight bar 4 being supported on the internal lugs of these arched walls.

The support of each end on the lugs is a ball joint, or articulation of the lattice on the hood, which can thus pivot about its longitudinal axis when both ends are engaged in the trestles being supported on these lugs.

This suspension of the mesh makes it possible to maintain it in a simple manner in position during the casting, in the soleplate, of the constituent concrete of the heel. As clearly visible in the figure 2 , the lattice is held in a position such that the lower straight bars 6 and 7 are located substantially at mid-height of the sole, to be embedded in the concrete of the heel being halfway up the latter so as to obtain the best possible cohesion.

As we see on the figure 2 , the cover 18 is further provided with lateral openings, marked respectively by 51 and 52, and allowing the entry of concrete into the shell of the beam during the casting of the compression slab. Each opening is at mid-length of the hood being located at the junction of an upper wall and a median wall thereof.

As shown in figure 2 , the sole 3 and the cover 18 have the same length along the direction AL. Each end of this set is delimited by a closed edge whose path is inscribed in a plane normal to the direction AL.

Each end of this assembly is closed by a tip, these tips being marked by 53 and 54 in the figure 3 . Each tip is a generally flat piece having a contour whose shape corresponds to the closed edge delimited by the end of the sole and that of the cover, so as to cover the entire opening defined by this edge, while fitting into the -this.

Each endpiece comprises a central opening, located opposite the cover 18. These openings which are marked respectively by 56 and 57 facilitate the entry of concrete into the shell during the casting of the compression slab.

In the example of Figures 1 to 3 , the beam according to the invention comprises only two arched walls, located at each of its ends. But it is also possible to provide a hood comprising three arched walls, namely a vaulted wall at each of its ends, and a third located midway between the two.

This variant is adapted to the case of a beam of greater length, as shown in FIG. figure 4 and it makes it possible to improve the maintenance of the lattice in its central zone by preventing it from sagging under the effect of its own weight.

The central arched wall, indicated by 58, also comprises an arched portion 59 extended by two flanks 61 and 62 connecting it to the median walls 27 and 31 of the cover 18. As shown in the figure, this central arched wall, which also includes spigots suspension of the lattice has a general shape corresponding to that of the two end vaulted walls 22 and 23 placed end to end.

In general, in the beam according to the invention, the sole ensures the protection of the cast heel concrete in the latter, so that the concrete of the heel is not likely to degrade, or thereby cause degradation wire mesh.

This heel is cast in a lightweight concrete, a density of less than 1.2 relative to water, as opposed to concrete usually used in such beams whose density is of the order of 2.4.

The lightweight concrete used is, for example, a concrete based on light aggregates such as expanded clay, perlite or other.

This sole which is also a mold for casting the heel is advantageously made of plastic material, just like the rest of the shell, which allows to further lighten this beam.

The combination of a lightweight concrete for the heel with a plastic shell allows to achieve a weight of between 7 and 8 kg per meter, allowing an operator to install the beam without having to resort to a hoist. Plastics are polypropylene (PP) or polyvinyl chloride (PVC), seeking the best possible adhesion with concrete heel. It is also possible to use a plastic material reinforced with fibers, a mineral filler or the like.

The presence of the cap provided with means for suspending the trellis singularly facilitates the manufacturing process of the beam on the production site: the simple fact of engaging the ends of the upper longitudinal bar of the trellis on the internal lugs of the cover is sufficient for the position relative to the sole when the hood is fitted on this sole.

This positioning of the lattice, suspended from the bonnet, furthermore makes it possible to comply with the fire resistance requirements, which result in a minimum distance to be respected between the lower face of the bead and the lower edge of the mesh encased in this bead.

Claims (7)

1. Beam (1) comprising a heel and a truss (2) rigidly secured to one another and extending in a longitudinal direction (AL), the truss (2) being an arrangement of steel bars (4, 6, 7, 8, 9) welded to one another which is partially embedded in the heel to secure it to this heel while partially projecting from a face of this heel termed the upper face, the heel is made of concrete and it includes a shell (3, 18, 53, 54), this shell (3, 18, 53, 54) covering and adhering to at least one of the faces of the heel, characterized in that the heel is made of lightweight concrete and the shell is made of polypropylene or polyvinyl chloride to increase the service life of this heel by protecting it from external attack.
2. Beam (1) according to claim 1, in which each end (22, 23) of the shell (3, 18, 53, 54) surrounds one end of the truss (2) and in which each end of the truss (2) is suspended from one end (22, 23) of the shell (3, 18, 53, 54).
3. Beam (1) according to claim 1, in which the shell (3, 18, 53, 54) comprises a sole plate (3) in the form of a plastic section having a generally U-shaped cross-section and two end pieces (53, 54) each nested at one end of the sole plate (3) so as to form a mould for casting the lightweight concrete of the heel.
4. Beam (1) according to claim 1 or 2, in which the shell (3, 18, 53, 54) also comprises a cap (18) which caps the sole plate (3) by nesting over it and in which each end (22, 23) of the cap (18) surrounds one end of the truss (2) whilst being provided with means (43, 44, 46) for keeping the truss (2) suspended from this cap (18).
5. Beam (1) according to claim 4, in which each end of the cap (18) is in the shape of a trestle (22, 23) and in which the means for keeping the truss (2) suspended are lugs (43, 44, 46) protruding from the internal faces of these trestles.
6. Beam (1) according to any one of claims 1 to 5, in which the truss (2) comprises three straight bars (4, 6 7) extending parallel to the heel, including two bars (6, 7) termed the lower bars embedded in the heel and a bar (4) termed the upper bar by which this truss (2) is suspended from the shell (3, 18, 53, 54).
7. Beam (1) according to any one of claims 1 to 6, comprising means for keeping the truss (2) suspended from the shell (3, 18, 53, 54) located between the ends of the truss (2) and of the shell (3, 18, 53, 54).

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