EP0296215B1 - Load carrying structures of low bulk density comprised of thin slabs and plates of reinforced concrete - Google Patents

Abstract

Tridimensional load carrying structure comprised of reinforced concrete slabs, of which the weight has been reduced by interior recesses. Said structure may be made by means of independent blocks (G) which are prefabricated and juxtaposed like cubes. The interior recesses may be obtained by means of cardboard boxes which are delivered folded in reduced volume. It is thus possible to build by means of these structures large lightened concrete load carrying beds, foundations or banks having very low densities. Tool outfit reference I, J, for prefabrication of independent blocks.

Description

It often happens, when the bearing capacity of the soil is not sufficient, that one is obliged to use expensive solutions to support buildings, heavy walls or traffic roads.

For example, if a large raft is used to distribute loads, the self-weight of this raft will significantly reduce the load of the building it is intended to support.

In other cases, when an embankment several meters high is to be carried out, the self-weight of this embankment added to the load of use will lead to settlements of the underlying soil.

The object of this patent is a load-bearing block according to claim 1 which makes it possible to propose solutions applicable to the two cases above, but not exclusively, by describing methods of economical manufacture of load-bearing structures composed of thin reinforced concrete veils and slabs so that the bulk density is low.

According to the invention, for the production of a load-bearing structure of low apparent density, hollow prefabricated load-bearing blocks of large dimensions are used, characterized in that each has thin vertical sails and horizontal thin reinforced concrete slabs, said slabs thin reinforced concrete which constitute the upper and lower faces of said block having openings and / or bosses.

The load-bearing blocks according to the invention are advantageously of parallelepiped shape, the vertical thin webs delimiting between them empty interior spaces. The vertical thin veils can constitute the end walls of the block, the empty space extending entirely inside said block, or at least some of the vertical thin veils can be arranged inside the apparent parallelepiped volume of the block by creating empty spaces which are extended by the juxtaposition of two adjacent blocks.

According to the invention, the carrier block has openings on its upper face and bosses on its lower face, or vice versa, the openings and bosses being designed so that the bosses presented by a block engage in the openings of a block adjacent ensuring horizontal keying. As a variant, the carrier block may have openings on its upper and lower faces, the openings facing two adjacent blocks being designed to receive an independent key.

A load-bearing structure of low apparent density, comprising a plurality of independent load-bearing blocks according to the invention, is characterized in that said blocks are juxtaposed in a horizontal plane by being keyed together and are superimposed in a vertical plane, each independent block having a low apparent density and comprising thin vertical walls of reinforced concrete and thin horizontal slabs of reinforced concrete.

Such a reinforced concrete load-bearing structure of low apparent density, composed of thin veils and slabs, is obtained by pre-fabrication by juxtaposing and superimposing independent blocks as in a construction with cubes, it being understood that these independent blocks, composed of slabs and thin reinforced concrete sails are also of low apparent density. These blocks are prefabricated, either in the factory, or better near the site, so as not to have to transport either large volumes or large tonnage.

The independent blocks of low apparent density are produced according to two processes:

- In the first process, we take light elements, which will constitute the interior of the blocks. At the lower part and at the perimeter, external forms are assembled so that the intervals between the light interior elements and the external forms are narrow. In these intervals there are steel reinforcements kept at a sufficient distance from the interior light elements and exterior formwork to comply with the rules for manufacturing reinforced concrete. Then we pour the concrete around the interior light elements and we finish by pouring at the top a thin slab also reinforced with steel reinforcements.

After setting the concrete and dismantling the external formwork, we will obtain a block composed of thin reinforced concrete walls and slabs, the interior containing the light elements, hence the low apparent density.

It is understood that the thickness of concrete and the steel reinforcements of the reinforced concrete walls and slabs are adapted to the load that the blocks will have to support.

In some cases, there are in the narrow intervals between light interior elements and exterior formwork, reservations of adequate shape so that the concrete does not completely fill the narrow intervals during casting. After formwork stripping, we will therefore find in slabs or thin concrete sails, and after eliminating reservations, hollows which constitute gaps between the inside and outside of the blocks.

It is also possible to make recesses in the external forms to create bosses outside the independent blocks.

Reservations will therefore be given to the openings that these will produce, and to the recesses in the external formwork therefore to the bosses external to the blocks, different positions and shapes depending on their function. By making openings in the lower part, each block will be able to fill with water in the event of flooding and thus not to receive an Archimedes thrust which could be harmful to the supported construction.

If we place the openings at the top, (A), they will allow the blocks to be grasped from above to transport them. If we make openings or bosses at the top and bottom, we can key the blocks together, either by placing them by means of ball joints, or by keying them at a certain distance from each other by means of independent keys. The independent keys are made either of concrete, or of metal, or even of elastomer; this latter solution will give more flexibility to the entire structure. By keying the independent blocks at a certain distance from each other, structures with an apparent density even lower than that of the independent blocks are produced.

If the reservations therefore, the openings in the reinforced concrete sails or slabs, are important, they allow the use of light removable interior elements which can be extracted through the openings after setting of the concrete and dismantling of the external forms.

the presence of openwork also makes it possible to use, as an interior light element, inflatable elements. After setting the concrete and removing the external formwork, the inflatable elements will be deflated and extracted. It is also possible to use partially inflatable, partially dismountable mixed systems and even lost light elements.

It is particularly advantageous to use light interior elements, of parallelepiped shape (B) and external formwork made up of flat plates with quick assembly because these make it possible to obtain parallelepipedic blocks. In this case the frames are made of folded welded mesh. (C) and (D). Any openings to be made in the sails are obtained by simple plates of the thickness of the sails, fixed on the flat plates of the external formwork. (E) and (F) as shown in Figure 3.

the lightweight parallelepiped elements, made of treated and reinforced cardboard, constitute a particularly economical solution. As for in situ manufacturing, they are delivered folded and are deployed only during the prefabrication of independent blocks

According to a second method, independent blocks of low apparent density are produced, only by assembling external formwork. These forms are provided with large bosses, of such form that after assembly of the external forms, they remain inside the blocks only at narrow intervals. Steel reinforcements are placed in these narrow intervals, keeping them at a distance from the external forms and the bosses which are fixed to them so that the rules for manufacturing reinforced concrete are observed.

When concrete is poured, the lower slab is first formed, then the vertical sails and finally the upper slab. The apparent volume of the blocks is parallelepipedic and allows juxtaposition and stacking. Without limitation: Boards 2 and 3 representing two embodiments G and H of these blocks and the corresponding tools (I - J and K - L).

The independent blocks can be juxtaposed to fill the bottom of a excavation, which allows for a light and relatively flexible raft. These blocks can be placed like fascines, which makes it possible to protect certain sites against shots, rockets or even explosions. Such achievements can be made in remote areas because the manufacturing tools are very rustic and easy to transport. It is enough to have concrete on site. After manufacture and installation of the blocks, it is possibly possible to ballast them.

These blocks used as light embankments allow the realization of embankments of several meters that can carry a pavement despite the poor working conditions of the underlying soil. These blocks have the advantage of long-term durability and if they are made with sufficient openings, they allow drainage easily through the embankments.

Prefabrication near the site allows for a very rapid installation of the light backfill since it is only a question of juxtaposing and stacking light blocks to handle.

By superimposing these blocks like large hollow bricks, it is possible to produce thick and load-bearing walls although remaining very light.

This process can be used for applications for underwater structures.

Claims (12)

1. A large-dimensioned prefabricated hollow support slab, characterised by thin vertical veils and thin horizontal flags of reinforced concrete, said thin reinforced concrete flags which comprise the upper and lower faces of said slab having gaps and/or bosses.

2. Support slab as in Claim 1 characterised by being of parallelepipidal shape, with the thin vertical veils defining between them hollow internal spaces.

3. Support slab as in Claim 2, characterised in that the thin vertical veils comprise the end walls of the slab, with the hollow space entirely disposed in the interior of said slab.

4. Support slab as in Claim 2, characterised in that at least some of the thin vertical veils are disposed within the apparent parallelepipidal volume of the slab by forming hollow spaces which are extended by the juxtaposition of two adjacent slabs.

5. Support slab as in any of Claims 1-4, characterised by having gaps on its upper face and bosses on its lower face, or vice-versa, the gaps and bosses being so designed that the bosses presented by one slab engage in the gaps of an adjacent slab to ensure horizontal keying.

6. Support slab as in any of Claims 1-4, characterised by having gaps on its upper and lower faces, the facing gaps of two adjacent slabs being designed to receive an independent key.

7. A support structure of low apparent density, comprising a plurality of independent support slabs (G.H) in accordance with any of Claims 1-6, characterised in that said slabs are juxtaposed in a horizontal plane while keyed together, and are superimposed in a vertical plane, each independent slab (G,H) having low apparent density and comprising thin vertical veils of reinforced concrete and thin horizontal flags of reinforced concrete.

8. Method of manufacture of a support slab in accordance with any of Claims 1-6, characterised in that on a lower formwork there is placed at least one light internal element (B) of low density and parellelepipidal shape, round this element there are disposed steel straps (C,D) held at sufficient distance from the light element (B) to conform with the rules on reinforced concrete fabrication, the entire assembly is surrounded by external formwork (E,F) comprising quickly assembled flat plates which only leave narrow gaps between themselves and the light internal elements (B), said gap being sufficient to comply with the rules on reinforced concrete fabrication, before pouring the concrete there are disposed spacers (A) which in the veils and thin flags define the gaps and/or bosses, the concrete being then poured to fill the available gaps between the veils and thin flags to form a block of low apparent density.

9. Method as in Claim 8, characterised in that the light parallelepipidal internal elements (B) are made of treated and reinforced cardboard, are delivered in folded condition and expanded to full size on site.

10. Method as in Claim 8, characterised in that the light internal elements are inflatable and recoverable.

11. Method as in Claim 8, characterised in that the light internal elements are made in sections and can be recovered, after dismantling of the external framework, via the gaps existing in the flags and thin veils.

12. Method of manufacturing a support slab complying with Claim 4, characterised by assembly of the external formworks (I,J.K,L) provided internally with bosses of such shape that only narrow gaps remain between said bosses, the steel straps are place thereon, spacers are formed at the levels of the upper and lower faces to define gaps and/or bosses in the narrow flags, the concrete being then poured to produce a block of apparent parallelepipidal volume whose thin vertical veils are disposed inside the volume, with empty spaces directed towards the exterior.

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