FR3095821A1 - Balcony slab and method of constructing a building - Google Patents

Abstract

Balcony slab and method of constructing a building Slab (11) to be mounted cantilever on a supporting structure (20), in particular balcony slab, prefabricated in concrete, comprising passages for prestressing reinforcement (14 ) intended for the application of a post-tensioning, these passages being formed therein during its manufacture. Figure for the abstract: Fig. 1

Description

Balcony slab and building construction method

The present invention relates to the construction of buildings and in particular the anchoring of a balcony slab in a load-bearing structure.

The construction of new concrete balconies generally involves the prefabrication of a slab with keying cast in place or by the formwork of the balcony cast in place.

In the presence of thermal bridge breakers, two anchoring solutions are generally used.

A first solution consists in using a continuous contact breaker, through which pass passive steels connecting the balcony slab to the load-bearing structure, which causes a possible problem of durability due to corrosion at the level of the contact breaker.

A second solution is based on the use of point anchorages via heavily reinforced reinforced concrete support sections, arranged between the breakers, which causes a concentration of forces in the support sections and poses both problems of realization due to the density of reinforcement and the quality of the concrete and deflection problems due to too much flexibility of the connection.

There is therefore a need to improve the production of balconies or other slabs extending cantilevered from a load-bearing structure, in particular in order to have a solution compatible with the presence of thermal breaks, easy to implement and offering the desired durability.

The invention aims to meet this need and has as its object, according to a first of its aspects, a slab to be mounted cantilevered on a load-bearing structure, in particular balcony slab, prefabricated in concrete, comprising passages for prestressing reinforcements intended for the application of a post-tension, these passages being formed therein during its manufacture.

The passages in question may be in the form of ducts. They can receive reinforcements such as sheathed strands.

Compared to the disadvantages associated with the state of the art mentioned above, the invention makes it possible to solve the problems of deflection, durability and implementation, without worsening, or even improving, the construction efficiency.

The invention is thus suitable for the construction of balconies of medium or large span, without the need for additional supports.

The invention allows the construction of balconies with thermal breaks, meeting current thermal regulations. The invention makes it possible in particular to use less expensive non-structural contact breakers.

In the case of the use of continuous breakers, that is to say extending over the entire length of the slab, and structural, the invention allows:

• to compensate all or part of the deflection under permanent load, which makes it possible to reduce the deflection in service and to increase the spans;
• not to crack or to limit the cracking of the concrete, which has a very favorable effect on the rigidity of the structure compared to its equivalent in reinforced concrete; By preventing the appearance of cracks, we offer better protection against water affecting the joint, despite the waterproofing layer, which contributes to the durability of the structure.

In the case of non-structural switches extending between discrete support sections, the invention allows:

• to compensate all or part of the deflection under permanent load, which makes it possible to overcome the flexibility consubstantial with the discretization of small-sized anchor points;
• not to crack or to limit the cracking of the concrete, with the advantages indicated above;
• to cross spans greater than those offered by traditional reinforced concrete.

In addition, the invention combines the advantages described above with those related to prefabrication, in particular concerning the quality of the facing and the stability of the mechanical and geometric characteristics offered by the industrialization of manufacture.

The slab can be delivered to the site already equipped with the prestressing reinforcements. These can be installed when the slab is prefabricated. The slab can thus include, within said passages, the prestressing reinforcements, intended for the application of a post-tension.

The passages, which may be in the form of ducts, may have been formed during the pouring of the concrete of the slab, in the thickness of the latter, and may only emerge at one end of the slab.

Rebars can have passive anchoring in the slab. In this case, active anchoring is carried out in the load-bearing structure, so as to be able to put the reinforcements under tension once the slab is in place.

As a variant, the reinforcements have an active anchoring in the slab, having for example one end bearing against an end of the slab opposite the load-bearing structure.

By "passive anchoring", it is necessary to understand an anchoring carried out in such a way that the end of the reinforcement occupies its final position within the concrete from the outset. By active anchoring, we designate an anchoring which makes it possible to move the end of the reinforcement relative to the concrete, to stretch it and generate a prestress within it.

The slab may comprise at least one housing for receiving a thermal switch. In this case it comprises for example at least two advances, also called support sections, by which it comes to bear on the supporting structure. The prestressing tendons preferably pass within each of these bearing sections, with for example one prestressing tendon per bearing section. The advantage of the support sections is to allow the use of non-structural contact breakers, arranged between them, not having to transmit a compressive force. These breakers fit between the support sections. The forces pass through the concrete support sections.

The slab may also include a structural continuous contact breaker on its side intended to be applied to the load-bearing structure.

The slab can already be pre-equipped with a guardrail when it is positioned against the load-bearing structure.

The slab is advantageously devoid of passive reinforcements such as irons, projecting out of the concrete thereof, to be embedded in the load-bearing structure. The absorption of shear forces at the interface is obtained by the concrete-concrete friction between that of the balcony slab and that of the load-bearing structure. Advantageously, the surfaces of the balcony slab and of the support structure coming into contact are given a combined shape, with complementary reliefs, for example a protruding relief on the slab and a recessed relief on the support structure, these reliefs s interlocking, or vice versa. An adhesive is preferably placed at the interface, for example an adhesive of the segment adhesive type, to eliminate the hard points.

In a variant, the concrete of the floor slab of the load-bearing structure is poured in contact with the balcony slab, which can simplify the making of the joint between the two.

Another subject of the invention, according to another of its aspects, is a building comprising a load-bearing structure and at least one prefabricated concrete slab extending cantilevered from this load-bearing structure, in particular a balcony slab as defined above, prestressing reinforcements, intended for the application of post-tension, connecting the cantilevered slab to the load-bearing structure, passages for the prestressing reinforcements having been formed in the cantilevered slab before assembly to the load-bearing structure.

The load-bearing structure may include a reinforced concrete floor slab, which is cast in place, after positioning the precast concrete slab. The free parts of the reinforcements anchored in the cantilevered slab are integrated into this slab of the load-bearing structure. Reservations into which the ends of the reinforcements open can be provided for the installation of active anchors, in order to put the reinforcements under tension.

The building may include discrete breakers at the interface between the cantilevered slab and the load-bearing structure, in which case the cantilevered slab advantageously bears against the load-bearing structure by support sections traversed by the reinforcing bars. prestressing, or alternatively a structural continuous breaker, crossed by the prestressing reinforcements and passive reinforcements.

Preferably, the reinforcements comprise sheathed strands.

The bearing surfaces of the cantilevered slab and of the slab of the load-bearing structure are advantageously combined, to help take up shear forces. A glue can be placed at the interface. The building can be made without passive reinforcement extending between the slab of the load-bearing structure and the cantilever slab.

The invention also relates to a method for constructing a building, comprising a supporting structure and at least one slab extending cantilevered from the supporting structure, in particular a balcony slab, method in which the cantilevered slab is brought into a precast state with pending reinforcements extending from the slab, a slab of the supporting structure is cast so as to embed the reinforcements therein, and the reinforcements are tensioned to prestress the cantilevered slab and ensure its hold on the load-bearing structure. The reinforcements are preferably non-adherent to the concrete when they are tensioned. The tensioning of the reinforcements can be carried out using active anchorages, for example at the level of reservations made in the slab of the load-bearing structure. The tensioning can be carried out using one or more cylinders, in particular with a nose, possibly with a curved nose when the deviation from the active anchorage is not sufficient to engage a straight nose cylinder.

The method may include the production of complementary reliefs between the slab of the load-bearing structure and the cantilevered slab, to help take up the shear forces.

The method may include the introduction of an adhesive at the interface between the slab of the load-bearing structure and the cantilevered slab.

The method may include the installation of thermal breaks between the slab of the load-bearing structure and the cantilevered slab. These thermal breaks may be non-structural, and extend between bearing sections of the cantilevered slab.

The invention may be better understood on reading the detailed description which follows, non-limiting examples of its implementation, and on examining the appended drawing, in which:

Figure 1 shows in perspective, schematically, a prefabricated balcony slab, in accordance with an example of implementation of the invention with discrete switch and tensioning from the inside,

Figure 2 illustrates the installation of the prefabricated balcony slab of Figure 1, provided with prestressing reinforcements and their anchoring, preinstalled, on a supporting structure,

Figure 3 is a schematic and partial section at right angles to a support section,

Figure 4 is a schematic and partial section at the level of the switch,

Figure 5 is a view similar to Figure 3 of an implementation variant with discrete breaker and tensioning from the outside,

Figure 6 shows detail VI of Figure 5,

Figure 7 is a view similar to Figure 4 of the implementation variant of Figure 5,

figure 8 shows detail VIII of figure 7,

figure 9 is a schematic and partial section of a variant with a running structural breaker and tensioning from the inside,

figure 10 is a schematic and partial section of a variant with a wire structure breaker and tensioning from the outside,

figure 11 shows detail XI of figure 10,

figure 12 is a schematic and partial section of a variant without a switch and with tensioning from the inside,

FIG. 13 is a diagrammatic and partial section of a variant without a breaker and with tensioning from the outside, and

figure 14 shows detail XIV of figure 13.

detailed description

The balcony 10 represented in FIGS. 1 to 5 comprises a balcony slab 11 prefabricated in reinforced concrete. The slab 11 comprises, on its side intended for assembly on a load-bearing structure 20, support sections 12, defining between them housings 13 in which non-structural switches 30 (one of which is visible on Figure 4).

The slab 11 can be pre-equipped with a guardrail 18, as illustrated, and can include lifting rings 16, anchored in the concrete.

In accordance with the invention, the slab 11 is made with prestressing reinforcements 14 anchored therein, embedded in the concrete of the slab 11.

These reinforcements 14 are preferably strands not adherent to the concrete of the slab, anchored therein at one end 14a, and which protrude at the other end from the support sections 12, with for example one reinforcement 14 per section d support 12, as shown.

The reinforcements 14 are, for example, 7-wire strands T15S (A=150mm2, fRG=1860 MPa, FRG=279kN) of the TGG (Greased Sheathed Strand) type, preferably 7-wire strands coated with grease and HDPE-sheathed.

The anchorages of these reinforcements 14 in the concrete of the balcony slab 11 constitute passive anchorages 31 (visible in FIG. 5).

The support structure 20 comprises for example, as illustrated in Figure 2, a floor slab 22 of reinforced concrete and a veil 24 provided with an opening 23 for access to the balcony 10.

The slab 11 is fixed to the floor slab 22 using the reinforcements 14.

The floor slab 22 is cast in place, in a conventional manner.

On the construction site, the slab 11 is presented and temporarily held bare from the floor slab 22 of the load-bearing structure, and the reinforcements 14 are deployed therein. Reservation boxes are positioned in the formwork of the floor slab 22 at each of the locations intended to receive the active anchors 15 of the reinforcements 14 in the floor slab 21 (not shown in FIG. 5).

In Figure 2, the floor slab 22 is shown after the pouring of the concrete and we see the reservations 21 intended to accommodate the active anchors 15 of the reinforcements 14.

After pouring the concrete of the slab 22, and hardening of the latter, the reinforcements 14 are tensioned from the active anchors 15, in order to generate a prestress in the slabs 11 and 22.

In order to limit the volume of these reservations 21, the reinforcements 14 are tensioned using cylinders fitted with a curved nose, which allow deflected tensioning above the floor slab 22.

The active anchors 15 of the reinforcements 14, after tensioning, are protected by cowling and/or sealing (not shown).

Due to the prestressing of the balcony slab 11, it is not necessary to provide reinforcement to ensure the connection between the balcony slab 11 and the floor slab 22.

We can provide a conjugation at the interface between the slab 11 and the slab 22, as well as a glue, for example of the type glue à voussoir, to eliminate the hard points.

Of course, the invention is not limited to the example which has just been described.

For example, it is possible to install passive anchoring of the reinforcements 14 within the slab 22 of the load-bearing structure. The active anchors can then be placed in reservations 34 opening out at the end of the prefabricated slab 11, then used for tensioning with a jack, as illustrated in Figures 5 to 7.

A layer of resin can be placed at the interface between the support sections 12 and the slab 22, as shown in Figure 6.

The active anchors present at the end of the slab can then be embedded in the concrete, for example, or otherwise protected.

It is also possible to use a running structural breaker 50, as illustrated in FIG. 9.

In this case, the balcony slab 11 is made without the support sections 12 and bears over its entire length against the structural breaker 50, which is interposed between the slabs 11 and 22 and transmits the compression forces between the two.

The switch 50 is crossed by the armatures 14 and by passive structural armatures.

In the example of figure 9, the tensioning is carried out from the inside, thanks to the reservations 21, like the example of figure 3.

In the variant of Figures 10 and 11, the tensioning is carried out from the outside, for example from the end of the balcony slab 11, like the example of Figure 5 previously described.

We see in Figure 11 that resin layers 51 and 52 can be interposed between the structural breaker 50 and the slabs 11 and 22 respectively.

In Figure 12, the possibility of applying the invention to a balcony without a thermal break has been illustrated.

In this case, the balcony slab 11 bears over its entire length directly against the slab 22.

The armatures 14 are tensioned from the inside, as in the example of Figures 1 to 4.

In the variant of Figures 13 and 14, the reinforcements 14 are tensioned from the outside, for example from the end of the slab 11, as shown.

A layer of resin 35 can be interposed between the tiles 11 and 22.

Claims (18)

Slab (11) to be mounted cantilevered on a load-bearing structure (20), in particular balcony slab, prefabricated in concrete, comprising passages for prestressing reinforcements (14) intended for the application of a post- tension, these passages being formed therein during its manufacture. Slab according to Claim 1, comprising within the said passages the prestressing reinforcements (14) intended for the application of a post-tension. Slab according to claim 2, the reinforcements (14) having a passive anchoring (31) therein. Slab according to claim 2, the reinforcements (14) having an active anchoring therein, preferably having one end bearing against an end of the slab opposite the load-bearing structure (20). Panel according to any one of the preceding claims, comprising at least one housing (13) for receiving a thermal cut-off (30). Slab according to claim 5, the housing (13) extending between two concrete support sections (12) of the slab (11). Slab according to one of Claims 1 to 4, comprising a structural continuous contact breaker (50) on its side intended to rest on the load-bearing structure (20). Slab according to one of Claims 1 to 4, being devoid of a thermal break and bearing directly over its entire length against the supporting structure (20). Building comprising a load-bearing structure (20) and at least one prefabricated concrete slab (11) extending cantilevered from this load-bearing structure, in particular a slab according to any one of the preceding claims, reinforcements ( 14) prestressing intended for the application of a post-tension connecting the cantilevered slab to the load-bearing structure, passages for the post-tensioning prestressing reinforcements having been formed in the cantilevered slab - false (11) before assembly to the supporting structure (20). Building according to the preceding claim, comprising discrete non-structural thermal breaks extending between bearing sections (12) of the balcony slabs (11). Building according to claim 9, comprising continuous structural breakers (50) extending between the balcony slabs and the load-bearing structure. Building according to claim 9, the balcony slabs bearing directly against the load-bearing structure, with the possible interposition of a layer of resin. Method of constructing a building, comprising a supporting structure (20) and at least one slab (10) extending cantilevered from the supporting structure, in particular a balcony slab, method in which the cantilevered slab in the prefabricated state with pending reinforcements (14) extending from the slab, a slab (22) of the load-bearing structure is cast so as to integrate the reinforcements (14) therein, and puts the reinforcements (14) under tension to prestress the cantilevered slab (10) and ensure its hold on the supporting structure. Method according to claim 13, the tensioning being carried out using at least one active anchoring (15), preferably at the level of each reservation (21) made in the slab of the load-bearing structure. Method according to claim 13, the tensioning being carried out using at least one nose jack, in particular with a curved nose. Method according to one of Claims 13 to 15, an adhesive being placed at the interface between the slab of the supporting structure and the cantilevered slab. Method according to one of Claims 13 to 16, thermal breakers being arranged in housings (13) extending between support sections (12) of the slab (11). Method according to one of Claims 13 to 16, at least one continuous structural thermal break (50) being interposed between the balcony slab (11) and the load-bearing structure (20).