EP1133605B1 - Embedded timber formwork element, floor cavity and spandrel using same - Google Patents

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

The present invention relates to the field of construction and building, and more particularly lost formwork elements which an application is constituted in the construction of floors, by interjoists and end eardrums.

Lost formwork elements are elements which, when associated with each other, delimit a volume in which a concrete is poured and which remain associated with concrete, this one once taken to form a coating.

The whole is therefore a composite material who must meet a number of requirements, particularly with regard to fire resistance and propagation fire. But it's the lost formwork elements that are in contact with the flame and it is they who, mainly, must have these qualities of resistance to fire and reaction to fire to meet tests, tests and standards in force. In this context, these lost formwork elements are then made in complex materials based on flame retardant components, which makes them expensive and calls for the implementation of manufacture whose performance is limited in terms of possible form.

Document CH-A-449 904 discloses a formwork lost for construction in reinforced concrete which is in matter plastic, thin-walled and ribbed on one side - As described, this product does not exhibit fire resistance.

Thanks to the specific measures of the invention, was allowed to make formwork elements lost in inexpensive thermoplastic material such as polyethylene, polypropylene, polyvinyl chloride (PVC) or polyethylene terephthalate (PET) and their derivatives, which can be produced by molding (injection) in various forms.

Thus, the subject of the invention is an element of lost formwork for a concrete structure that is realized in a flammable thermoplastic material, shaped in thin walls, and consistent with the characterizing part of claim 1.

We realized that the anchorage distributed, which results from the presence of these reliefs, has for result the fact that in the presence of a fire on the side of the formwork element lost, only a fusion very local plastic material with an evacuation important of the heat of the concrete side that plays the role an effective energy dissipator. It follows that the formwork element does not come off the concrete block and therefore only ignites very easily.

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

The optimal 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 side of which they are spared and secondly to the extent that the the surfaces of the reliefs perpendicular to the aforementioned face of the element is minimal, just necessary for demolding of the element during its manufacture. It was also realized that, if the qualities of resistance mechanical allow, the thickness of the wall (basic that is to say with the exception of the reliefs) is weak, best are the qualities of the product with regard to the fire. That is why the thickness of the base wall is included between 1.5 and 2.5 mm while the reliefs are formed preferably by parallel and / or intersecting ribs of height between 0.8 and 2 mm and also between 0.8 and 2 mm with a pitch or a spacing between 8 and 10 mm.

Finally, the surface condition of the element on its face next to the concrete will be advantageously rough in order to create micro asperities that promote intimate contact between the concrete and the formwork element. These micro roughnesses will be obtained by surface treatment (mechanical or chemical) walls of the injection mold.

An interesting application of the element according to the invention consists of a interjoists for the realization of building floor in association with two joists at prestressed heel or reinforced concrete and parallel. according to the invention, the wall of the interjoists is limited by two parallel longitudinal edges and two transverse edges end and this wall affects a general shape bent around a direction parallel to these two edges longitudinal, with its textured side convex side, this wall having a view of this convex side, depressions transverse parallels evenly spaced others that define a succession of compartments in open boxes on the concave side.

Finally, the invention also finds a interesting application when done under form of an end eardrum intended to complete a Entrevous bay. This tympanum has a wall substantially vertical whose external profile is similar to the profile of a cross section of a interjoists, equipped with one side of a horizontal sole at level of the underside of the beam and the other side of a gutter housing the end of the last enter the bay. The textured side of this tympanum is that which is in continuation of the concave face of the gutter.

• les figures 1 à 3 illustrent différentes texturations d'un élément de coffrage selon l'invention,
• la figure 4 est une vue partielle extérieure d'un entrevous conforme à l'invention du côté de sa face convexe,
• la figure 5 est une vue en coupe transversale de cet entrevous,
• la figure 6 est une vue en coupe longitudinale partielle illustrant l'empilage de deux entrevous et la coopération de deux entrevous adjacents.
• la figure 7 est un schéma illustrant de manière partielle la coopération d'un entrevous selon l'invention et de deux poutrelles adjacentes de plancher,
• les figures 8 et 9 illustrent divers détails de réalisation de l'entrevous selon l'invention,
• la figure 10 est une vue d'un tympan selon l'invention.

Other features and advantages of the invention will become apparent from the description given below by way of example of some embodiments. Reference will be made to the appended drawings among which:

• Figures 1 to 3 illustrate different texturations of a formwork element according to the invention,
• FIG. 4 is an external partial view of a interlock according to the invention on the side of its convex face,
• FIG. 5 is a cross-sectional view of this interjoists,
• Figure 6 is a partial longitudinal sectional view illustrating the stacking of two interjoists and the cooperation of two adjacent interjoists.
• Figure 7 is a diagram partially illustrating the cooperation of a interjoists according to the invention and two adjacent floor beams,
• Figures 8 and 9 illustrate various details of embodiment of the interjoists according to the invention,
• Figure 10 is a view of a tympanum according to the invention.

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

The element according to the invention has a base wall P whose thickness is denoted e in the figures and whose face F is provided with reliefs R. In Figures 1 and 2 these reliefs are simply constituted by parallel ribs whose width l may vary for example between 1.2 and 3 mm. The height h of these grooves can vary from 0.8 to 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 between 8 and 10 mm and, in the case of Figures 1 to 3 equal to 8 mm.

In Figure 3, the reliefs R are formed by a network of intersecting ribs which define nodes N1, N2, which are sometimes at a maximum altitude relative to the surface F, sometimes to a minimum. When the thickness e of the plate is of the order of 2.5 mm, the mesh represented has a dimension of 8 mm, the altitude of the lower nodes N2 is of the order of 0.8 to 1 mm while the The altitude of the upper nodes is about 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 nodes N1 higher. In the example under consideration, this thickness varies between 0.8 and 1.2 mm.

In addition, according to the invention, the surface F of the element P and the upper surfaces of the reliefs (or the lateral surfaces of these), have a rough appearance resulting for example from a treatment either chemical or mechanical injection mold of which take out these formwork elements. This rough appearance has for the sake of improving the contact of concrete and the formwork element.

Examples above we understand that the realized reliefs have dimensions that are of the order the thickness of the base wall P of the element. The thickness of this base wall will not be greater than 2.5 mm, even if it is ribbed and consistent to behave like the elements in caissons if the mechanical constraints that must supporting these formwork elements require it. This thickness of 2.5 mm was determined by calculation and verified experimentally: beyond that, it seems that the role of heat sink of the concrete compared to siding is reduced and that the qualities of the material to be fire and its spread are clearly decreased.

One of the important applications of the element lost formwork according to the invention is a interjoists. We recall that in certain types of achievements, a floor consists of a series of T-beams or heel, parallel, usually prestressed concrete or armed, between which we set up a filling - intertwined everything is then covered with a compression table made of cast concrete with a metal frame.

These elements have the function on the one hand to ensure a continuous circulation area of workers on the building site before finishing the floor and, on the other hand, to form a formwork for realizing the compression table that forms the wall of the floor proper, above the joists and in between, this wall can be covered or not of a slab.

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

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

Thanks to the invention, it is possible to realize a light interjoists using a ribbed thin wall to offer significant resistance to an applied effort against this wall (weight of a man or weight of a concrete thickness) made of a plastic material cheap and light. For this purpose, in a preferred mode of embodiment, this wall is limited by two edges parallel longitudinal and two transverse edges end and affecting a generally curved shape around of a direction parallel to its longitudinal edges, this wall having, seen from its convex side, depressions transverse parallels evenly spaced others that define a succession of compartments in open boxes on the concave side. This interview confers on the underside of a compression table a box structure, that is to say a succession of small vaulted parts, separated by ribs cross beams extending from one beam to the other, this which gives a particularly resistant character to the compression table that can only be one thick 4 cm above each interjoists.

Of course the interjoists have properties particularly interesting with regard to fire and its spread like the lost formwork element exposed above. The texturing of its convex surface constitutes plus an anti-slip function for workers who circulate on the interjoists.

Thus, in FIGS. 4 to 7, there is shown by two exterior views convex surfaces (Figure 4) and concave (FIG. 7) of a wall 1 of constant thickness which is this interview. This wall 1, limited by two longitudinal edges 2 and 3, is usually bent around a direction parallel to these two edges. A value possible thickness of the wall is about 2 mm.

This wall has transverse deformations 4 which appear as depressions on the side convex and in the form of ribs on the concave side of them. These depressions or ribs define a compartmentalization of the interjoists which is then under form of compartments 5 open on the concave side.

More specifically, the bottom wall 5a of each compartment is planar with, viewed from the convex side, a central recess 6 provided with a grid array of ribs 7 (Figures 4 and 6). Always on the convex side, the surface of the interjoists is worked in order to increase its roughness and therefore the surface that will be in contact with the concrete of the compression plate to promote its anchoring to this concrete. This texturing can affect various shapes: pimples arranged next to each other, pimples whose head is crushed to form a mushroom, a tight grid, a tight grid whose top of the ribs is also crushed to create against undercut surfaces forming retention concrete, more or less closely spaced grooves ... This texturing is partially shown in Figure 4, 8 has referred to the planar areas of the interjoists (intersecting array of ribs as shown in Figure 3 by example) and 8b for other areas (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 contact between you and concrete. It has therefore been possible to envisage the manufacture by injection molding intervous in an extremely inexpensive material such as polypropylene, which, in addition to the advantages related to the weight and the volume of a thin-walled interjoists is a non-negligible factor on the cost of manufacturing such a device.

The standard longitudinal dimension of a interjoists may 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 sealing between them with respect to the concrete is provided by, for example, the overlap of two end gutters 9 which are formed along the transverse edges of the interjoists. These gutters 9 have substantially the same section as the bottom of each depression 4 and their longitudinal profile (transverse to the interjoists) is the same as that of the bottom of each depression 4 and at the same altitude as this one. In addition, these overlapping gutters staple each other by means of breakable tongues or other devices in fir teeth formed in one of the gutters cooperating with openings provided for this purpose in correspondence in the other of the gutters. A detail of Figure 6 illustrates the cooperation of two adjacent interjoists by overlapping their gutter 9 and a locking edge 9a of one of the channels in a retaining tooth 9 b on the other.

As it is unlikely that all floors are a multiple of 150 mm, it is necessary to provide means to adjust the length of interjoists to the length of the beams that accommodate them. These means are shown in FIGS. 4 and 6 by transverse marks such as 10 which constitute sawing guides for the interjoists. The sawed interjoists are attached to each other simply by juxtaposition and to preserve the seal is put in place adhesive tape straddling the joint. This tape is at the same time a sign of avoidance for the workers brought to circulate on interjoists. In this way, it will be appreciated that the texturing 8a of the upper surface of each of the compartments is interjoists plus a propagating area for good cooperation concrete - plastic, non-slip means for the workers circulating on these floors under construction. It is also possible to saw a intervous depression bottom 4 and adjust the length of a span using the tympanum shown in Figure 10.

It is also possible to predict in the wall of interjoists, breakable zones with resistance weakened, for example holes to be opened 11 provided in appropriate places and in particular in the parts planes of the wall of each compartment and this, by example, at a determined fixed step. These breakable areas or holes to unclog allow to put in place before the pouring concrete a number of inserts, passages or of reservations by which subsequent equipment of the floor is easy. For the same functional reasons, it is quite possible to foresee each or some of the depressions 4 of the studs 12 likely to accommodate self-tapping screws for the suspension of various accessories. It is also possible to provide housing 13, especially at the top of the ribs 4 views of the concave side, in which can be slipped all kinds of fasteners and especially harpoons 14 to retain a layer of insulation (Figure 8).

It is interesting to note that the constitution of a intervous 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 interjoists rests substantially in the angle a formed by the heel 16a of the beam 16 with its core 16 b. This leaves out a part of the heel 16 is under the interjoists part that can be leveraged for hanging heavier load suspension elements have under the floor as eg false ceilings elements 17. This This possibility does not exist in known interiors known as concrete or polystyrene because these interjoists totally occupy the angle A of each beam 16.

Finally, the longitudinal end of each can be equipped with a gasket or a part flexible which will ensure a certain tightness between the joist and the interjoists in order to avoid flows of concrete laitance. This seal can be a lip is in one piece with the interjoiself itself be reported in the longitudinal edge of it suitably shaped to receive this lip.

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

Note also that the interview according to the invention comprises (see FIG. 4) along one of its longitudinal edges a handle 18 for its handling. Since each interview is not very heavy, a worker can take in hands several interjacent ones piled up on the others, as in figure 6, by means of the handles 18 which correspond, thus making it possible to decrease very substantially handling operations on site.

Before setting up the interjoists between two beams, we break the handle 18 and we can use this one as a means of wedging interstices in particular against the uprising under the effect of the wind by placing this handle 18 straddling a beam 16 that it encloses elastically (see Figure 7).

The element shown in Figure 10 is a tympanum intended to complete a span of interjoists between two beams. This eardrum essentially has a wall substantially vertical 20 whose outer surface visible has a texture-style grooves such as represented in FIGS. 1 and 2, this vertical wall being extended by a sole 21 which is substantially perpendicular whereas at the opposite of this sole 21 the tympanum is provided in one piece with the wall vertical 20 of a gutter 22. The gutter 22 is intended to receive either the end 9 of a interjoists or one end of it that would have been cut out in the depression. 4. Indeed, it can be foreseen that the between you are not cut along lines 10 length adjustment of a span to the length of the beams that delimit it but only in the depths of each of the depressions 4. It seals between the tympanum and interjoists with regard to poured concrete. So the tympanum provides firm support at one end interwoven and seals against concrete sank.

The profile of the wall 20 is substantially identical to the transversal profile of a interjoists at the level of each of the caissons while the dimension parallel to joists of the sole 21 which is at the level of the surface of the beams, may be such as to allow 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 Figure 3. Gussets 24 extend between the sole 23 and the wall 20 as stiffeners interjoists. Side flanges 25 a is finally noted, 25 b which rest on the heels of the beams and which have the function of sealing between the eardrum and the joists.

Preferably, each eardrum is drawn from a pair of eardrums obtained by injection into an impression double, symmetrical to each other in relation to a line median corresponding to the outer edge of the sole of every eardrum.

Claims (11)

1. A permanent formwork element for a concrete structure, the element being made of an inflammable thermoplastic material shaped to form a thin wall (P) that is ribbed on one face, the element being characterized in that the thickness of said wall lies in the range 1.5 mm to 2.5 mm, in that the face (F) of said wall that is to come into contact with concrete is provided in full with texturing in the form of portions (R) in relief of height (h) and width (ℓ) that are of the same order as the mean thickness of the wall (P), and that are spaced apart by an amount lying in the range 8 mm to 10 mm so as to provide the element with anchoring to the concrete that is distributed over all of the above-mentioned face (F) and so as to provide an increased area of contact between the element and the concrete in order to encourage heat exchange between them.
2. A formwork element according to claim 1, characterized in that the surface for making contact with concrete is rough.
3. A formwork element according to either preceding claim, characterized in that it is made of injection-molded polypropylene.
4. A floor block constituting an application of the element according to any preceding claim for making a building floor in association with two parallel joists (16), the floor block being characterized in that the wall (1) is defined by two parallel longitudinal edges (2, 3) and by two end transverse edges (9) and takes on a shape that is generally curved about a direction parallel to its two longitudinal edges (2, 3), with its textured face being on the convex side, said wall (1), when seen from its convex side, including parallel transverse depressions (4) that are regularly spaced apart from one another and that define a succession of box compartments (5) that are open to the concave side.
5. A floor block according to claim 4, characterized in that the section of a depression (4) in the wall on a plane parallel to its longitudinal edges is V-shaped, thus defining ribs for the bottom face of the compression panel, said ribs extending transversely relative to the joist
6. A floor block according to claim 4 or claim 5, characterized in that its convex surface includes rectilinear marks (10) parallel to the depressions (4) and forming guide lines for cutting the floor block transversely.
7. A floor block according to any one of claims 4 to 6, characterized in that the wall portion (5a) forming the top of each box (5) is substantially plane and includes zones of weakness (11) that are regularly spaced apart from one another so as to be easily separable from the remainder of the wall.
8. A floor block according to any one of claims 4 to 7, characterized in that it includes a separable handle (18) extending along one of its longitudinal edges.
9. A floor block according to any one of claims 4 to 8, characterized in that it includes end gutters (9) similar in shape and in disposition to the bottom of each depression (4) and including snap-fastening means (9a, 9b) for engaging with the gutter of an adjacent floor block.
10. An end face constituting an application of the permanent formwork element according to any one of claims 1 to 3 for finishing off a span of floor blocks according to claim 4 at the end of flanged joists (16), the end face being characterized in that it comprises a substantially vertical wall (20) of outside profile similar to the profile of a cross-section of a floor block, and fitted on one side with a horizontal soleplate (21) level with the bottom face of the joist, and on the other side with a gutter for receiving the end of the last floor block of the span.
11. A floor made using floor blocks (1) according to any one of claims 4 to 9, and parallel flanged beams (16), the floor being characterized in that each of the longitudinal edges (3, 4) of the floor blocks rest in the corner (A) between a flange and a joist, thus releasing the end-most portion of each flange (16a) of the joist which is left accessible for other uses.

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