WO2000031355A1

WO2000031355A1 - Embedded timber formwork element, floor cavity and spandrel using same

Info

Publication number: WO2000031355A1
Application number: PCT/FR1999/002710
Authority: WO
Inventors: Jean Roux; Christian Herreria; Jean-Paul Py; Farid Sahnoune
Original assignee: Bedaricienne Doras Industries
Priority date: 1998-11-26
Filing date: 1999-11-05
Publication date: 2000-06-02
Also published as: AU1052400A; DE69926073T2; EP1133605A1; FR2786514B1; FR2786514A1; DE69926073D1; ES2245517T3; ATE299212T1; EP1133605B1

Abstract

The invention concerns an embedded timber formwork element for a concrete structure produced in a flammable thermoplastic material shaped in the form of a thin wall (P) whereof the surface (F) designed to be in contact with the concrete is provided with a texturing in the form of raised parts (R) whereof the height is of the order of the wall thickness, whereby the area of the element in contact with the concrete is increased and its anchoring in the concrete is ensured.

Description

Lost formwork element, interjoists and tympanum applying.

The present invention relates to the field of construction and building, and more particularly to lost formwork elements of which an application is constituted, in the construction of floors, by interjoists and end eardrums. The lost formwork elements are wall elements which, associated with each other, define a volume in which a concrete is poured and which remain associated with the concrete, the latter once taken to form a coating. The assembly therefore constitutes a composite material which must meet a certain number of requirements, in particular as regards fire resistance and fire propagation. However, it is the lost formwork elements which are in contact with the flame and it is they which, mainly, must have these qualities of fire resistance and reaction to fire to satisfy the tests, tests and standards in force. In this context, these lost formwork elements are then produced in complex materials based on flame retardant components, which makes them expensive and requires the implementation of manufacturing methods whose performance is limited in terms of possible shape.

Thanks to the specific measures of the invention, it was possible to produce lost formwork elements in inexpensive thermoplastic material such as polyethylene, polypropylene, polyvinyl chloride (PVC) or polyethylene terephthalate (PET) and their derivatives. , able to be produced by molding (injection) in the most varied forms. Thus, the subject of the invention is an element of lost formwork for a concrete structure which is made of a flammable thermoplastic material, shaped into thin walls, the face of which intended to be in contact with concrete is provided with a texturing in the form of reliefs whose dimensions are of the order of the thickness of the wall. These reliefs forming the texturing of this surface are therefore distributed over the entire surface and constitute the means for anchoring the element to the concrete which is also distributed. We have in fact realized that this distributed anchoring, which results from the presence of these reliefs, results in the fact that in the presence of a fire on the side of the lost formwork element, we only find that a fusion of the very local plastic with a significant evacuation of the heat on the side of the concrete which plays the role of an efficient energy dissipator. It follows that the formwork element does not come off as a block from the concrete and therefore only ignites with great difficulty.

This lack of detachment is a very important factor in the non-propagation of the fire and the composite material formed by the concrete and its thermoplastic facing belongs to the category of materials which is the least conducive to transmitting fire whereas the thermoplastic material alone does not not meet this criterion at all.

The optimum of the qualities of the material with regard to the fire is obtained on the one hand, when the reliefs have dimensions (height, width ...) which are of the order of the average thickness of the wall on one face of which they are provided and on the other hand insofar as the clearance of the surfaces of the reliefs perpendicular to the aforesaid face of the element is minimal, just necessary for demolding of the element during its manufacture. We also realized that, if the qualities of mechanical resistance allow it, the thickness of the wall (basic that is to say with the exception of the reliefs) is weak, the better the qualities of the product with respect to the fire. This is why, in a preferred embodiment, the thickness of the base wall is between 1.5 and 2.5 mm while the reliefs are formed by parallel and / or intersecting ribs with a height between 0 , 8 and 2 mm and also between 0.8 and 2 mm in width with a pitch or gap less than 10 mm. Finally, the surface condition of the element on its face opposite the concrete will advantageously be rough in order to create micro asperities which promote intimate contact between the concrete and the formwork element. These micro roughnesses will be obtained by a surface treatment (mechanical or chemical) of the walls of the injection mold. An interesting application of the element according to the invention consists of a glimpse for the production of a building floor in association with two prestressed heel beams or reinforced parallel concrete. According to the invention, the wall of the interjoist is limited by two parallel longitudinal edges and two transverse end edges and this wall has a general shape curved around a direction parallel to these two longitudinal edges, with its textured face of the convex side, this wall having a view from this convex side, transverse parallel depressions regularly spaced from one another which define a succession of compartments in open boxes on the concave side.

Finally, the invention also finds an interesting application when it is produced in the form of an end eardrum intended to complete, a span of interjoists. This eardrum has a substantially vertical wall whose external profile is similar to the profile of a cross section of a interjoist, fitted on one side with a horizontal flange at the level of the underside of the beam and on the other side of a housing gutter at the end of the last interjoist of the span. The textured side of this eardrum is the continuation of the concave side of the gutter. Other characteristics and advantages of the invention will become apparent during the description given below by way of example of some embodiments. Reference will be made to the appended drawings, in which: FIGS. 1 to 3 illustrate different textures of a formwork element according to the invention,

- Figure 4 is a partial exterior view of a interjoist according to the invention from the side of its convex face, - Figure 5 is a cross-sectional view of this interjoist, Figure 6 is a partial longitudinal sectional view illustrating 1 stacking of two interjoists and the cooperation of two adjacent interjoists. FIG. 7 is a diagram partially illustrating the cooperation of a interjoist according to the invention and of two adjacent floor joists,

- Figures 8 and 9 illustrate various details of embodiment of the interjoist according to the invention, - Figure 10 is a view of a tympanum according to

1 invention.

Figures 1 to 3 are partial diagrams of a formwork element according to the invention, seen from the side of their surface intended to be in contact with concrete. The material used will preferably be polypropylene but may also be polyethylene, polyvinyl chloride or PET.

The element according to the invention has a base wall P whose thickness is denoted e in the figures and one face F of which is provided with reliefs R. In FIGS. 1 and 2 these reliefs are simply constituted by parallel ribs whose width 1 can vary for example between 1.2 and 3 mm. The height h of these grooves can vary between 0.8 and 1.2 mm, the thickness e of the base plate being of the order of 1.5 to 2.5 mm. The pitch between the ribs is less than 10 mm and, in the case of the figure, equal to 8 mm.

In FIG. 3, the reliefs R are formed by a network of intersecting ribs which define nodes NI, N2, which are sometimes at a maximum altitude relative to the surface F, sometimes at a minimum. When the thickness e of the plate is of the order of 2.5 mm, the mesh shown has the dimension of 8 mm, the altitude of the lower nodes N2 is of the order of 0.8 to 1 mm while 1 the altitude of the upper nodes is approximately 2 mm above the surface F. In addition, it will be noted that the thickness of these ribs is in the variable figure with a maximum in the vicinity of the lower nodes N2 and a minimum in the vicinity of the upper NI nodes. In the example considered, this thickness varies between 0.8 and 1.2 mm.

In addition, in accordance with the invention, the surface F of the element P and the upper surfaces of the reliefs (or even the lateral surfaces of these) have a rough appearance resulting, for example, from either a chemical or mechanical treatment of the injection mold from which these formwork elements emerge. This rough aspect has the advantage of improving the contact between the concrete and the formwork element. From the examples above, it is understood that the reliefs produced have dimensions which are of the order of the thickness of the base wall P of the element. Preferably, the thickness of this base wall will not be greater than 2.5 mm, even if it is to be ribbed and shaped to behave like the elements in boxes if the mechanical stresses that these formwork elements have to bear require it. This thickness of 2.5 mm has been determined by calculation and verified experimentally: beyond this, it would seem that the role of heat sink of the concrete with respect to the facing is reduced and that the qualities of the material with regard to fire and of its spread are significantly reduced.

One of the important applications of the formwork element lost according to the invention is an interjoist. It will be recalled that in certain types of embodiments, a floor comprises a series of T-beams or heels, parallel, generally made of prestressed or reinforced concrete, between which a filling is placed - in between - the whole then being covered with a compression table made of poured concrete with a metal frame.

These elements have the function on the one hand of ensuring a surface for the continuous circulation of workers on the site before the floor is finished and, on the other hand, of forming a formwork for producing the compression table which forms the wall of the floor. proper, above the beams and interjoists, this wall may or may not be covered with a slab.

The spacing between two beams fixed by the manufacturer and adapted to the width of the interjoists (of the order of 60 to 70 cm). The length of the interjoist can be equal to a few meters if this interjoist is made of light material such as polystyrene or 20 to 25 cm if the interjoist is made of concrete. This dimension is dictated by the weight of the interjoist which is generally handled by hand on the site.

All known interjoists are produced in the form of hollow boxed and partitioned elements, the thickness is between 8 and 25 cm, each longitudinal edge of the interjoist coming to rest on the heel of a T-beam. These are bulky and heavy elements whose transport is penalizing. As the concrete interjoists are small to be of a weight compatible with manual handling, it is necessary to transport a lot to make a floor.

Thanks to the invention, a light interjoist can be produced using a thin ribbed wall to offer significant resistance to a force applied against this wall (weight of a man or weight of a thickness of concrete) made in a cheap and light plastic. To this end, in a preferred embodiment, this wall is limited by two parallel longitudinal edges and two transverse end edges and having a general shape curved around a direction parallel to its longitudinal edges, this wall comprising, seen from its convex side, transverse parallel depressions regularly spaced from each other which define a succession of compartments in open boxes on the concave side. This interjoist gives the underside of a compression table a box structure, that is to say a succession of small arched parts, separated by transverse ribs extending from one beam to another, this which gives a particularly resistant character to the compression table which can be only 4 cm thick above each interjoist.

Of course, the interjoist has particularly interesting properties with regard to fire and its propagation, like the lost formwork element exposed above. The texturing of its convex surface is also an anti-slip function for workers who circulate on the interjoist. Thus, in Figures 4 to 7, there is shown by two exterior views of the convex (FIG. 4) and concave (FIG. 7) surfaces of a wall 1 of constant thickness which constitutes this interjoist. This wall 1, bounded by two longitudinal edges 2 and 3, is generally curved around a direction parallel to these two edges. A possible value for the wall thickness is around 2 mm.

This wall has transverse deformations 4 which appear in the form of depressions on the convex side and in the form of ribs on the concave side thereof. These depressions or ribs define a partitioning of the interjoist which then takes the form of compartments 5 open on the concave side.

More specifically, the bottom wall 5a of each compartment is planar with, seen from the convex side, a central recess 6 provided with a grid network of ribs 7 (Figures 4 and 6). Still on the convex side, the surface of the interjoist is worked in order to increase its roughness and therefore the area which will be in contact with the concrete of the compression plate in order to promote its anchoring to this concrete. This texturing can take various forms: spikes arranged one next to the other, spikes whose head is crushed to form a mushroom, tight grid, a tight grid whose top of the ribs is also crushed to create undercut surfaces forming retention of concrete, more or less closely spaced grooves ... This texturing is partially represented in FIG. 4, referenced 8a for the flat areas of the interjoist (network of intersecting ribs as in FIG. 3 for example ) and 8b for the other zones (parallel ribs as in Figures 1 and 2 for example). The role of this texturing of the convex surface of the plate 1 forming interjoists is as said above to increase the intimacy of the interjoist-concrete contact. It was therefore possible to envisage the manufacture by injection molding of interjoists in an extremely inexpensive material such as polypropylene, which, in addition to the advantages linked to the weight and volume of a thin-walled interjoist, is a non-negligible factor in the cost of manufacturing such a device. The standard longitudinal dimension of an entrance hall can for example correspond to 1.20 m or 1.50 m with a compartment width measured at the bottom of depression 4 equal to 150 mm. The longitudinal connection of two interjoists and the seal between them with respect to the concrete is ensured by, for example, the overlapping of two end gutters 9 which are formed along the transverse edges of the interjoist. These gutters 9 have substantially the same section as the bottom of each depression 4 and their longitudinal profile (transverse to the interjoist) is the same as that of the bottom of each depression 4 and at the same altitude as the latter. In addition, these overlapping gutters s' staple each other by means of breakable tabs or other devices in fir teeth formed in one of the gutters cooperating with openings provided for this purpose in correspondence in one other gutters. A detail in FIG. 6 illustrates the cooperation of two adjacent interjoists by overlapping their gutter 9 and snap-fastening of an edge 9a of one of the gutters under a retaining tooth 9b of the other.

As it is unlikely that all floors are a multiple of 150 mm, it is advisable to provide means to adjust the length of the interjoists to the length of the beams which accommodate them. These means are represented in FIGS. 4 and 6 by transverse marks such as 10 which constitute sawing guides for the interjoist. The sawn interjoists join each other quite simply by juxtaposition and to preserve the sealing an adhesive tape is put in place on the joint. This adhesive tape also constitutes time a sign of avoidance for the workers brought to circulate on the interjoists. In this regard, moreover, it will be noted that the texturing 8a of the upper surface of each of the compartments of the interjoists constitutes, in addition to a multiplication of surface area intended for good cooperation between concrete and plastic, non-slip means for the workers traveling on these floors under construction. It is also possible to saw a cross-piece at the bottom of the depression 4 and to adjust the length of a span using the eardrum shown in FIG. 10.

It is also possible to provide in the wall of the interjoist, breakable zones with weakened resistance, for example through holes 11 provided in suitable places and in particular in the flat parts of the wall of each compartment and this, for example , at a fixed fixed step. These breakable zones or unblocking holes allow a number of inserts, passages or reservations to be put in place before pouring the concrete, thereby facilitating subsequent fitting of the floor. For the same functional reasons, it is entirely possible to provide at the bottom of each or some of the depressions 4 of the studs 12 capable of accommodating self-tapping screws for the suspension of various accessories. It is also possible to provide housings 13, in particular at the top of the ribs 4 seen from the concave side, into which all kinds of fixing members can slide, in particular harpoons 14 to retain a layer of insulating product (FIG. 8).

It is interesting to note that the constitution of a glimpse in the form of a thin wall has the advantage illustrated by FIGS. 7 and 9. This advantage lies in the fact that each of the longitudinal edges 2 and 3 of the glove rests practically in angle A that forms the heel 16a of the beam 16 with its core 16b. This leaves an entire part of the heel 16a uncovered under the interjoist, a part which can be used to hang suspension elements of greater load to be placed under the floor such as for example elements of false ceilings 17. This possibility does not exist in the known concrete or polystyrene interjoists because these interjoists totally occupy the angle A of each beam 16. Finally, the longitudinal end of each interjoist can be equipped with a joint or a flexible part which will ensure a certain seal between the beam and the interjoist to avoid the flow of laitance from concrete. This seal can be a lip either in one piece with the interjoist itself or attached in the longitudinal edge of the latter suitably shaped to receive this lip.

It is not outside the scope of the invention to provide a material other than the thermoplastics injected to produce such interjoists. Indeed, it is possible to imagine the manufacture of these devices from stamped metal sheets or even thermoformed plastic sheets.

It will also be noted that the interjoist according to the invention comprises (see FIG. 4) along one of its longitudinal edges a handle 18 for its handling. As each interjoist is not very heavy, a worker can take in hand several interjoists stacked on each other, as in FIG. 6, by means of the handles 18 which correspond, thus making it possible to very significantly reduce the handling operations on construction site.

Before putting in place the interjoist between two beams, the handle 18 is broken and it can be used as a means of wedging interjoists in particular against lifting under the effect of the wind by placing this handle 18 straddling a beam 16 which it elastically encloses (see FIG. 7).

The element shown in Figure 10 is a tympanum intended to complete a span of interjoists between two beams. This eardrum essentially comprises a substantially vertical wall 20 whose visible external surface has a texture of the grooves style as shown in FIGS. 1 and 2, this vertical wall being extended by a sole 21 which is substantially perpendicular to it while, on the opposite side of this sole 21 the eardrum is provided in a single piece with the vertical wall 20 of a gutter 22. The gutter 22 is intended to receive either the end 9 of a interjoist or an end thereof which would have been cut out in the bottom of a depression 4. In fact, it is possible to provide that the interjoists are cut not along lines 10 for adjusting the length of a span to the length of the beams which delimit it, but only at the bottom of each depressions 4. It provides a seal between the eardrum and the interjoist with respect to the poured concrete. Thus the eardrum constitutes a firm support at one end of the interjoist and ensures sealing with regard to the poured concrete.

The profile of the wall 20 is substantially identical to the transverse profile of a interjoist at each of the boxes while the dimension parallel to the beams of the sole 21 which is at the bottom surface of the beams, may be such that it allows an adjustment of the order of 1 to 10 centimeters with respect to the support 23 on which the beams 16 rest.

The sole 21 is textured for example as shown in FIG. 3. Gussets 24 extend between the sole 23 and the wall 20 by way of stiffeners in the interjoist. Finally, note the side edges 25a, 25b which rest on the heels of the beams and which have the function of ensuring a seal between the eardrum and the beams.

Preferably, each eardrum is taken from a pair of eardrums obtained by injection into a double impression, symmetrical to one another with respect to a median line corresponding to the outer edge of the sole of each eardrum.

Claims

1. Formwork element lost for a concrete structure, characterized in that it is made of a flammable thermoplastic material shaped into a thin wall (P) whose face (F) intended to be in contact with concrete is provided with texturing in the form of reliefs

(R) whose height (h) is of the order of the thickness of the wall, to ensure an anchoring distributed over all of said face (F) of the element to the concrete.

2. Formwork element according to claim 1, characterized in that the surface in contact with the concrete is rough.

3. Formwork element according to claim 1 or claim 2, characterized in that the thickness of the base wall (P) is between 1.5 and 3 mm while the reliefs are formed by ribs (R) parallel and / or intersecting between 0.8 and 2 mm in height and between 0.8 and 2 mm in width with a pitch or spacing between them at most equal to 10 mm.

4. Formwork element according to one of the preceding claims, characterized in that it is made of injected polypropylene.

5. interjoists applying the element according to one of the preceding claims for the production of building floors in association with two parallel beams (16), characterized in that the wall (1) is limited by two edges (2, 3) parallel longitudinal and two edges (9) transverse end and has a generally curved shape around a direction parallel to its two longitudinal edges (2, 3), with its textured face on the convex side, this wall (1) comprising view from its convex side, parallel depressions (4) transversely spaced from one another and defining a succession of compartments (5) in open boxes on the concave side.

6. interjoist according to claim 5, characterized in that the section of a depression (4) of the wall by a plane parallel to its longitudinal edges is V-shaped, thus defining a ribbing of the underside of the plate compression, transverse to the beams.

7. interjoists according to one of claims 5 and

6, characterized in that it has on its convex surface rectilinear marks (10) parallel to the depressions (4) forming a guide line for its transverse cutting.

8. interjoists according to one of claims 5 to

7, characterized in that the wall portion (5a) forming the bottom of each box (5) is substantially planar and regularly spaced from each other, weakened resistance zones (11) so as to easily separate them from the rest of the wall.

9. interjoists according to one of claims 5 to

8, characterized in that it comprises a separable handling handle (18) along one of its longitudinal edges.

10. interjoists according to one of claims 5 to

9, characterized in that it includes gutters (9) with similar ends in shape and arrangement at the bottom of each depression (4) and comprising snap-fastening means (9a, 9b) with the gutter of a interjoist adjacent.

11. end tympanum applying the formwork element lost according to one of claims 1 to 4 and intended to complete a span of interjoists according to claim 5 at the end of the heel beams (16) characterized in that it comprises a substantially vertical wall (20) whose external profile is similar to the profile of a cross section of a interjoist, fitted on one side with a horizontal sole (21) at the level of the underside of the beam, and the other side of a gutter (22) for receiving the end of the last interjoist of the span.

12. Floor made by means of interjoists (1) according to one of claims 5 to 10, and beams (16) with parallel heel, characterized in that each of the longitudinal edges (3, 4) of the interjoists rests in the 'angle (A) of the heel and the beam, thus freeing the most extreme part of each heel (16a) of the beam left accessible for other uses.