WO2009087321A1

WO2009087321A1 - Prefabricated element for creating a reinforced concrete slab and slab thus created

Info

Publication number: WO2009087321A1
Application number: PCT/FR2008/050023
Authority: WO
Inventors: Philippe Matiere
Original assignee: Societe Civile De Brevets Matiere
Priority date: 2008-01-07
Filing date: 2008-01-07
Publication date: 2009-07-16
Also published as: EP2231947A1; EP2231947B1; ATE526465T1

Abstract

The subject of the invention is a prefabricated element for creating a reinforced concrete slab (D) comprising at least two longitudinal metal girders (2), a reinforced concrete sheet (3) in which the lower sole plates (21) of the girders (2) are embedded, and means of transverse connection between the longitudinal girders (2), the said concrete sheet (3) constituting formwork for pouring a layer of concrete (11) in which the longitudinal girders (2) are embedded so as to form a slab (D). According to the invention, the means of connection between the longitudinal girders (2) consist of two layers of reinforcements (4, 4') running transversely between the respectively lower (21) and upper (22) sole plates of the said girders (2) and fixed ridgidly thereto so as to form, with the said girders (2), a monolithic cage of metalwork capable of withstanding the bending loads applied in the longitudinal direction and in the transverse direction by collaborating with the sheet of concrete (3), particularly while the element (1) is being transported and laid on its supports (61, 7). The invention makes it possible, in particular, to create the deck of a bridge resting on at least two spaced-apart supports.

Description

PREFABRICATED ELEMENT FOR THE PRODUCTION OF AN ARMED CONCRETE SLAB AND SLAB THUS REALIZED

The invention relates to a prefabricated element for the realization of a reinforced concrete slab and also covers a slab thus produced and its manufacturing process. For the construction of buildings or certain structures, it is often necessary to make slabs of reinforced concrete comprising a metal reinforcement embedded in the concrete, between two faces of facing, generally parallel.

For the realization of horizontal slabs, formwork panels are placed on which the reinforcement is placed and then the concrete is poured on the desired thickness.

It is also possible to place between the supports prefabricated beams spaced apart from each other between which are placed shuttering panels for the casting of the slab, the prefabricated beams being provided with connectors to be secured to the slab after the setting of the concrete . The dimensions of such prefabricated beams are limited by the possibilities of lifting and handling.

For medium and large spans, it is possible to use prefabricated elements of the "slab-beam" type each forming a ribbed concrete beam with an upper flange constituting a part of the floor, but such elements are relatively heavy and fragile.

In another known method, for the realization of a slab having a range of a few meters, is placed between two supports I-section parallel metal beams between which are arranged thin plates which bear on the lower flanges of the beams of to form, between them, a formwork for pouring concrete to form a slab in which are embedded the metal beams. These thin plates are put in place manually and must therefore be quite light but, because of this, the thickness of concrete that can flow over the plate is limited.

On the other hand, the installation of these thin plates between the beams is not easy and is carried out, usually, by operators themselves. moving on previously laid beams. These operations are, therefore, quite dangerous since they are performed above the vacuum and, even after the installation of the formwork plates, they are not designed to withstand a fall. It is therefore necessary to provide protections that complicate the process and reduce the interest.

In addition, when pouring concrete, leaks can occur at the junction between the thin plates and the flanges of the beams.

In addition, the outer faces of the metal soles remain apparent and must therefore be painted and maintained regularly.

To avoid this drawback, it was therefore the idea to drown the lower flanges of the metal beams in a concrete pre-slab forming a formwork for pouring concrete to a thickness sufficient to drown the lower part of the metal beams and therefore constituting the lower face of the thick slab thus produced.

Document FR-A-2 851 779, for example, describes a prefabricated element of this type comprising at least two parallel metal beams each having a core, an upper flange and a lower flange embedded in a concrete slab. In addition, the webs of the two metal beams are connected at their lower part by hitching irons which extend laterally projecting from the concrete plate to ensure the transverse connection between the adjacent prefabricated elements.

Such a method is normally provided for the realization of low transverse solicited floors. Document FR-A-2 851 779 aims to improve the transverse strength of the structures thus produced by means of the hitching irons which extend laterally projecting from the sole. In this way, it is possible to make the rails of a crossing structure. However, in such a method, the bending resistance is provided by the metal beams, the concrete serving essentially as coating. As a result, the concrete plate connecting the lower flanges of the metal girders is subjected to stresses which risk cracking it, in particular during the transport and laying of the prefabricated element. This disadvantage can be avoided by subjecting the beams during the pouring of the concrete slab, an elastic deformation which, after loosening, makes it possible to prestress the concrete slab. In practice, however, the implementation of such a method is quite complex, in particular for the realization of works having a relatively large scope, of the order of 15 m, for example.

However, it is necessary to realize very quickly concrete slabs or crossing structures of such a range, for example for the coverage of an urban highway. In this case, the work must be done in a short time, usually during the night, so as not to stop the traffic for too long a period.

However, in urban sites, it is sometimes difficult to use bulky hoisting equipment of great power and it is therefore necessary to limit the weight of the prefabricated elements and, consequently, that of the concrete plate in which are drowned the lower flanges of the metal girders. This connecting plate may therefore not have sufficient strength to prevent the overturning of the beams. In addition, to achieve large spans, of the order of 15 m, the width of the element must be limited, for example to 2 or 3 m. Such a relatively narrow band-shaped member tends to twist, especially during lifting operations, which increases the risk of cracking.

Furthermore, it is advantageous, in order to obtain sufficient resistance to bending, to ensure true cooperation between the metal reinforcement and the concrete whereas, in the method of document FR-A-2 851 779, this resistance is provided. only by the metal beams.

The invention provides a solution to such problems thanks to a new type of prefabricated element that is both lightweight and strong, comprising a monolithic reinforcement cage capable of withstanding the bending forces in all directions by cooperating, in addition, perfectly with the concrete slab during the transport and laying of the element and, in use, with the concrete of the slab.

The invention thus makes it possible to realize quickly, economically and safely reinforced concrete slabs possibly having spans. relatively large, may exceed 10 meters, with a relatively small thickness, of the order of 500 to 600 mm.

The subject of the invention is therefore, in general, a prefabricated element for producing a reinforced concrete slab, of the type comprising at least two longitudinal metal beams each having at least one core, a lower flange and a flange. upper sole plate, a reinforced concrete plate in which the lower flanges of the metal beams are embedded, and means for transverse connection between the longitudinal beams, said concrete slab constituting, after the element has been laid on spaced apart supports, a formwork for casting a concrete layer in which the longitudinal beams are embedded so as to form the slab.

According to the invention, the connecting means between the longitudinal beams consist of two transverse reinforcement plies extending respectively to the lower flanges and to the upper flanges of said beams and fixed rigidly thereto so as to forming with said beams a monolithic reinforcement assembly capable of withstanding the bending forces applied in the longitudinal and transverse directions cooperating with the concrete plate, during transport and laying of the element on its supports.

In a preferred embodiment, the two reinforcing plies each comprise a plurality of spaced transverse bars, welded on the outer faces of the flanges, respectively upper and lower, longitudinal beams, and a plurality of longitudinal bars welded on said transverse bars. .

Particularly advantageously, at least the outer faces of the flanges, respectively upper and lower longitudinal beams, are provided with protruding connectors so as to ensure the bonding of the beam with the concrete which enrobe.

Preferably, the vertical core of each metal beam has a perforated structure having concrete passage openings on either side of the beam through the vertical core. According to another particularly advantageous characteristic, the concrete plate in which the lower parts of the beams are embedded, has a width compatible with the possibilities of transport by road or rail. On the other hand, the concrete slab may be extended at right angles along at least one of its lateral sides by a portion raised so as to form a cornice having a height at least equal to the thickness of the slab. slab to achieve.

Similarly, the concrete slab can be extended at right angles along at least one of its transverse sides by a raised portion forming a cornice in which is embedded the corresponding end of each longitudinal beam.

The invention thus makes it possible to produce a slab or a platform of any width resting on at least two spaced apart supports. But it is also possible to make several consecutive bays based on intermediate supports.

In this case, at at least one of its ends, each metal beam is extended beyond the corresponding transverse side of the plate, by a connecting portion extending in a console and can be secured to a corresponding part of the plate. a metal beam of a next element.

In another embodiment, of an element according to the invention, the two reinforcing plies respectively form with the sole plates of the beams, the lower part and the upper part of at least one tubular reinforcement cage extending between two longitudinal beams substantially along their entire length and secured thereto by solder points made at least at the upper flanges and lower flanges.

The invention also covers a method for producing a prefabricated element comprising the following steps:

placing, on a plane support, at least two parallel metal beams spaced apart from one another, each having a core, a first sole placed on the support and a second sole; - laying on the second soles of the beams of a plurality of transverse bars and welding thereof over the entire width of the sole;

- laying on the transverse bars of a plurality of longitudinal bars and welding them with the transverse bars so as to form a first reinforcing ply;

- Turning the assembly and laying metal beams and the first layer on the support;

- laying on the first flanges of the metal beams of a plurality of transverse bars and welding thereof over the entire width of soles;

- laying on said transverse bars and welding therewith a plurality of longitudinal bars so as to form a second ply of reinforcements; - Making a hollow prefabrication mold having a substantially planar bottom, and at least four sides, respectively two longitudinal sides and two transverse sides;

- Establishment in the mold of the monolithic reinforcement cage consisting of longitudinal beams secured by the two reinforcing plies, a minimum coating distance being maintained between the longitudinal bars of the lower ply and the bottom of the mold;

pouring concrete into the mold so as to cover the bottom thereof to a thickness sufficient to encompass the lower portions of the metal girders and the lower reinforcing ply,

- stripping after setting and hardening of the concrete to obtain a prefabricated element comprising at least one longitudinal metal beam having a bottom flange and an armor ply sealed in a reinforced concrete plate capable of constituting a formwork for the pouring of a reinforced concrete slab by the monolithic reinforcement cage constituted by the beams secured by the two plies of reinforcement.

Such prefabricated elements allow for a reinforced concrete slab resting on at least two spaced apart supports. According to the invention, at least one prefabricated element is placed on the supports and the lower concrete plate is surrounded by shuttering elements extending vertically over a height at least equal to the thickness of the slab to be produced, this being obtained by pouring concrete into the mold thus formed and whose plate constitutes the bottom, to a thickness sufficient to completely drown the reinforcement cage.

Advantageously, at each of the supports, the concrete slab is provided with a recess in which at least one connecting piece is provided at the desired location on the support for sealing the slab with the support. by pouring concrete into said recess.

In a first embodiment, the slab consists of at least two prefabricated elements placed next to each other with at least two adjoining adjacent sides and two outer sides along which the concrete slab is provided with a raised portion constituting a formwork element for pouring concrete into the mold thus formed.

In a second embodiment, the slab consists of at least two elements placed one after the other in the longitudinal direction with joining the adjacent ends of the metal beams.

Other advantageous features of the invention will appear in the following description of certain particular embodiments, given as simple non-limiting examples and illustrated by the accompanying drawings.

Figure 1 shows schematically in cross section the realization of a prefabricated element according to the invention.

Figure 2 is a cross-sectional view of a slab formed from two elements placed side by side.

Figure 3 shows a first example of use of prefabricated elements for the realization of a building.

Figure 4 shows two variants of the junction between the plates.

FIG. 5 schematically shows, in perspective, the production of a bridge plate by means of prefabricated elements according to the invention. FIG. 6 shows, in cross section, an example of a lower passage made by means of prefabricated elements according to the invention.

Figure 7 is a partial view, in cross section, of the deck of such a lower passage.

Figure 8 is a detail view, in section, of a recess.

Figure 9 is a side view of a composite bridge deck resting on an intermediate support.

FIG. 10 is a partial sectional view of the plate of FIG. 9.

Figure 11 shows the connection between two consecutive elements at the intermediate support.

FIG. 12 is a view from below along the line 1-1 of FIG. 1. FIG. 13 is a sectional view along the line II-II of FIG.

1 1.

Figure 14 is another example of junction between two consecutive plate elements with offset support.

Figure 15 shows, in cross section, another embodiment of a prefabricated element according to the invention.

Figure 16 shows, in cross section, another embodiment of a slab consisting of two elements according to Figure 15, placed side by side.

FIG. 1 diagrammatically shows, in cross-section, a first embodiment of a prefabricated element 1 according to the invention comprising, in the example shown, three beams 2 made of I or H section metal sections. whose lower part is sealed in a plate 3 of reinforced concrete.

Normally, the beams 2a, 2b, 2c are parallel to a longitudinal direction of the element 1, that is to say perpendicular to the plane of Figure 1 and each comprise a vertical core 20 and two flanges 21, 22, the lower sole 21 being embedded in the concrete plate 3. In addition, the three beams 2a, 2b, 2c are connected by two reinforcing plies, respectively an upper ply 4 and a lower ply 4 'embedded in the concrete plate 3.

The upper sheet 4 consists, in a conventional manner, of a plurality of transverse bars 41 and longitudinal bars 42 spaced from each other and distributed, respectively, along the length and the width of the element. However, according to the invention, the transverse bars 41 are applied directly to the outer faces 23 of the upper flanges 22 of the three beams 2a, 2b, 2c and, in addition, are fixed thereto, by weld points 43 distributed over the entire width of the sole 22 or by a continuous weld seam. In this way, each transverse bar 41 is secured to the upper flanges 22 of the three beams 2a, 2b, 2c.

The longitudinal bars 42 spaced from each other and distributed over the entire width of the element, are placed above the transverse bars 41 and fixed thereto by welding.

Similarly, the lower ply 4 'consists of transverse bars 41' and longitudinal bars 42 ', the transverse bars 41' being applied and welded to the outer faces 23 'of the lower flanges 21 of the three beams 2a, 2b, 2c, the lower longitudinal bars 42 'being placed below the lower transverse bars 41' and fixed thereon by welding. The lower ply 4 'is thus embedded with the flanges 21 in the concrete plate 3, the thickness of which must be sufficient for the longitudinal bars 42' fixed on the transverse bars 41 'and the lower flanges 21 to be at a distance minimum coating (b) of the underside of the plate 3.

In general, moreover, the characteristics of the metal reinforcement cage constituted by the beams (2) and the two reinforcing plies (4, 4 '), as well as the thickness (e) of the plate ( 3), are determined so that, after demolding, all of the element thus produced can be handled, transported and put in place on spaced apart supports and that, in addition, the plate 3 can withstand certain loads or shocks accidents and the weight of the concrete 1 1 which, as discussed below, is poured over the plate 3 including the beams 2 to form a slab D.

In particular, the number of metal beams 2, their dimensions, their spacing I and the characteristics of the two reinforcing plies will be determined as a function of the loads to be borne by the slab D made by means of the element 1, as well as the possibilities handling and laying thereof, in particular lifting devices that are available at the construction site.

However, according to an essential characteristic of the invention, because the two reinforcing plies 4,4 'are welded directly on the outer faces 23, 23', respectively of the upper sole 22 and the lower sole 21 of the three metal beams 2, the assembly constitutes a monolithic reinforcement cage, relatively rigid and dimensionally stable, able to withstand the stresses, in particular the bending forces applied in the longitudinal direction and in the transverse direction, cooperating with the concrete plate 3 during transport and installation of element 1 on its supports.

In particular, since the main longitudinal reinforcements consist of I-section or H-section metal sections, each section of the reinforcement cage comprising two sections on which the transverse bars 41, 41 'are welded constitutes an indeformable rectangle and It is therefore unnecessary to provide connecting stirrups between the two reinforcing plies.

In addition, the transverse bars 41, 41 'respectively welded to the outer faces of the upper flanges 22 and lower flanges 21 oppose the overturning of the sections 2 so that the concrete plate 3, strongly reinforced by the bars 41' 42 'of the lower sheet 4', is not likely to crack during transport of the element after demolding. Such a prefabricated element can, in fact, be made in a mold 10 having a bottom 101 preferably rectangular, two lateral sides 102 and two transverse sides 103.

If necessary, it is possible to place at the bottom of the mold 10 a fur intended to obtain, after stripping, a slight counter-arrow of the element in the longitudinal direction, for example of the order of 5 cm for 15 m in length.

In addition, before casting concrete 1 1, it would also be possible to place, in some of the rectangular spaces between the metal beams 2, the upper sheet 4 and the concrete plate 3, one or more tubes 18 of plastic, forming conduits for the passage of pipes, electric cables or other circuits.

To make an element 1, the reinforcement cage is first of all prefabricated by placing one next to the other, on a plane support, the metal beams 2a, 2b, 2c on which the transverse bars 41 are then placed. which are welded to the outer faces 23 'of the flanges 21, over the entire width thereof. Then the longitudinal bars 42 'are laid and welded on the cross bars 41'. Connectors 24 'are also fixed on the flanges 21. The assembly thus produced can then be turned over so as to allow the laying and welding of the transverse bars 41 on the flanges 22 equipped with connectors 24, then longitudinal bars 42.

A metal reinforcement cage has thus been formed comprising three beams 2a, 2b, 2c whose soles are secured by the two reinforcing plies 4, 4 '.

A certain amount of concrete is then poured into the bottom of the mold 10, to the desired thickness, then the metal cage is put in place so that the beams 2 rest, by their lower flanges 21 on the fresh concrete in which sink the reinforcing bars 41 ',

42 'and the connectors 24'.

Preferably, a minimum coating distance (b) relative to the bottom of the mold is maintained by unrepresented spacers.

The mold is then filled with concrete 1 1 to a height (e) for example of the order of 10 to 20 cm, so as to completely embed the armature ply 4 ', the connectors 24' and the lower parts beams 2, giving the desired resistance to the plate 3.

After the setting and hardening of the concrete, the prefabricated element 1 thus produced can be removed and transported to the construction site. According to another preferred feature, the total width L of the element, between the lateral sides 30 of the plate 3 will be determined so as to respect the road traffic gauge. Thus, such an element may be prefabricated in the factory at a distance from the construction site and then transported to it by rail or road, the element being placed lengthwise on a trailer. This width L may therefore be of the order of 2.5 m, the element 1 preferably comprising three beams 2 spaced apart by about 0.8 m.

On the other hand, the length of the element can be much more important. For example, a length of 10 to 15 m still allows transport on a conventional road trailer.

A prefabricated element thus produced can be particularly strong while remaining relatively flexible, given its length, while maintaining, however, a weight compatible with the lifting possibilities normally available on a site of some importance, by example for the realization of a bridge or a passage under.

Such an element can therefore be handled and placed on supports spaced in the longitudinal direction, the elements being placed side by side in a number to cover the desired surface.

FIG. 1 shows a standard element comprising a plurality of metal beams 2 rigidly connected by the two reinforcing plies 4, 4 ', the assembly being sealed at the base in a plate 3 which is extended laterally, Beyond the beams 2a, 2c, a free length (I / 2) preferably equal to half the gap between the beams 2.

For the realization of a floor, it is possible to place side by side several elements 1, 1 'in sufficient number to cover the desired surface, taking into account the width L of an element, a seal 35 being interposed between the sides opposite the concrete plates 3 of the two elements 1, 1 '.

As shown in FIG. 2, the transverse bars 41 of two adjacent elements 1, 1 'can be extended beyond the junction plane P and associated with longitudinal bars 43 to ensure the joining of the two upper reinforcing plies. at the level of the plane P. Similarly, at the lower part of the junction zone, short transverse bars 44 associated with longitudinal bars 43 'can be placed on the upper faces of the plates 3, 3' between the webs 20c, 20'a of the two beams. longitudinal adjacent 2c, 2'a. After laying the elements 1, 1 ', it is possible to put in place unrepresented forms applied on the lateral and transverse sides of the plates 3 which then form the bottom of a mold in which concrete 1 1 can be cast until at a level greater than that of the soles and upper reinforcing plies of the two elements 1, 1 'in order to drown the entire reinforcement. This produces a concrete slab D of total height (h) that can cover the desired surface.

Since I-section or H-section metal sections are used as main longitudinal reinforcement, the total height (h) of the D-slab, of equal strength, may be less than that of a concrete slab. classical weapon comprising two reinforcing plies connected by stirrups.

However, thanks to the connectors 24 fixed on the outer faces 23, 23 'of the flanges 22, 21 of the beams 2, they cooperate perfectly with the concrete 3, 11 in which they are embedded, thus forming a composite structure in which the concrete and the reinforcement cage work in complementarity and in all directions to participate in the resistance of the slab. It can, moreover, work in a hyperstatic manner, for example in the part resting on piles when the prefabricated elements are used to achieve several consecutive bays, as will be seen later.

To avoid the laying of a formwork, it is also possible, during the molding of certain prefabricated elements, to arrange on one of the lateral sides of the plate 3, a raised portion 36 which preferably extends over the height (h) to give the slab and is a kind of cornice. In the example shown in Figure 2 of a floor consisting of two elements placed side by side, one of the lateral sides of each of the elements 1, 1 'is provided with a cornice 36, 36', the other two sides of the plates 3, 3 'joining along the longitudinal joint plane P, in which is interposed a seal 35. It is thus possible to make a slab more or less armed depending on the loads to bear.

As indicated above, it is advantageous to produce elements of great length, for example from 10 to 15m, but of width limited to 2m or 2.5m in order to comply with the standard road gauge, the elements can thus be prefabricated in the factory then transported to the construction site.

In the case shown in Figure 2 of a slab D consisting of two elements 1, 1 'placed side by side, thus producing a slab that can have a width of about 5 m. But it is possible, of course, to increase this width by placing, between the two elements of side 1,

1 'a central element without cornice of the type shown in Figure 1.

As shown diagrammatically in FIG. 3, such a technique makes it possible, for example, for a building or a parking lot, a floor 5 resting on walls or rows of spaced apart pillars 50.

It is thus possible to produce slabs placed on supports, for example neoprene. In this case, the transverse ends 51 of the slabs can be formed, either by a removable formwork or by a portion raised cornice.

But it is also possible to make continuous slabs by leaving the profiles and the longitudinal reinforcement 42 in the space 52 between two successive slabs 5, this space being then concreted.

In the case, for example, of a parking lot, it is also possible to make a recess in the four peripheral walls framing the slab longitudinally and laterally. Such embedding can be achieved for example in the manner shown in Figure 8 which will be described later.

On the other hand, as shown in Figure 4, to improve the junction between the adjacent elements and avoid, in particular, a strumming effect, the adjacent sides 30, 30 'of the plates 3, 3' of two neighboring elements can be provided with thinned or recessed, recessed and projecting parts which fit into one another when the elements are laid, with the interposition of a seal 35. As indicated above, the use, as main reinforcements, of metal beams 2 cooperating with the reinforcing plies 4, 4 ', the concrete slab 3 and the concrete 1 1 of the slab D, makes it possible to produce prefabricated elements of great length being able to rest, at their ends, on supports separated by a distance being able to exceed the 15 m.

It is thus possible to make bridges comprising several consecutive spans, as will be described in detail below, with reference to FIGS. 9 to 14. However, it is also possible to use transverse slabs resting, by the central part of the concrete plate, on two spaced apart supports, for example to realize the platform of a mixed structure bridge comprising two main metal beams 53 on which rests the reinforced concrete platform, according to the arrangement shown schematically in Figure 5.

As previously, the platform 5 of the bridge, which rests on two longitudinal beams 53 apart, consists of a plurality of prefabricated elements 1, 1 'each comprising several metal beams 2 whose base is sealed in a concrete plate 3. In Figure 5 to simplify the drawing, a single beam 2 has been shown for the prefabricated element 1b and the reinforcing bars 41, 42 are only partially indicated.

In this case, the two main beams 53 on which the platform 5 of the bridge lies are separated by a distance L2 less than the length L1 of the element which thus comprises a central portion 3a extending between the two beams 53 and two parts 3b extending cantilevered.

By placing, one beside the other, a number of such elements 1, 1 '... resting across the main beams 53 it is possible to achieve a platform 5 of any length. In this case, each element 1 is provided, at its two longitudinal ends, with raised portions 56 which, as previously, extend at right angles to the transverse sides 38 of the plate 3 and extend to above the level of the upper flanges. beams 2 so as to form transverse cornices 56 in which are included the ends 23 of the beams 2.

In addition, during the prefabrication of each element 1, housings 57 can be reserved in these transverse cornices 56 to facilitate the assembly of unrepresented railings.

Preferably, the elements 1 placed at the ends of the platform 5 are provided, as in the case of Figure 2, a raised portion 36 parallel to the beams 2 and forming a lateral formwork. These lateral raised portions 36 and transverse 56 form a self-formwork for pouring concrete 1 1 to embed the beams 2 and thus form the platform of the bridge.

Advantageously, the concrete plate 3 is provided, at the level of the main beams 53 on which the platform 5 rests, recesses 37 which pass through the plate 3 over its entire height and are placed between two parallel longitudinal beams 2. The corresponding zones of the main beams 53 are then provided with connectors 54 welded to the upper flange 55 of the beam 53 and which engage in the recesses 37 at the laying of the prefabricated element 1 which can thus be sealed to the main beams 53 by casting concrete in the recesses 37.

It is thus possible to realize a wide-width composite bridge platform consisting of a slab 5 sealed on the two main beams 53 and being able to extend cantilevered on either side of them, thanks to the strong reinforcement constituted by the metal beams 2 and the two layers of upper bars 4 and lower 4 '. This avoids the placement of brackets which are usually welded to the frame beams 53 to maintain the parts of the platform extending cantilevered on either side thereof. As a result, the underside of the platform can remain smooth, which facilitates the implementation, for maintenance, of rolling carriages suspended below the platform, without breaking the rolling at each console.

Of course, the platform 5 thus produced could be based, if necessary, on more than two main beams 53. Similarly, one could achieve a platform of very large width by placing two lines of prefabricated elements on four main beams. The realization of such a bridge is easier and safer than by the old methods. As already indicated, the plate 3 being relatively thick and armed, during the prefabrication of each element, by the lower sheet 4 'welded to the soles 21, it is no longer necessary to provide a fall protection for setting up and sealing the elements. These can only be fitted with temporary guardrails attached to the upper flange of the metal beams 2.

By using elements of great length, for example from 10 to 15 m, it is possible to produce a multi-track platform by means of a relatively small number of elements. The number and length of seals to be placed between the plates 3 of the elements placed side by side is also reduced compared to conventional methods, which reduces the risk of burrs or loss of milt concrete and allows, possibly, the use of self-placing concrete much more fluid than in known methods and easy to implement, even without vibration.

By way of example, FIGS. 6 and 7 show the production of a lower passage by means of prefabricated elements according to the invention. Such a lower passage comprises, for example, a platform 6 resting on two spaced apart abutments 61 which may advantageously consist of juxtaposed prefabricated elements, each comprising a vertical wall forming a cross-piece 61 and provided at its base with an enlarged sole 62 enabling this pedestrian element is simply placed on the bottom of a trench T. Preferably, each pedestal element 61 is provided at its upper part with an enlarged part 63 on which the platform 6 which can be constituted, as shown in Figure 7 of a plurality of prefabricated elements in the manner shown in Figure 1 and each comprising a concrete plate 3 in which are sealed the lower flanges of two or three metal beams 2. For the making a bridge allowing the lower passage of three or four lanes, the distance between L3 support may be of the order of 15 m, the l very metallic 2 being dimensioned accordingly to present the inertia necessary for the recovery of the own weight of the elements and loads applied. The assembly may be covered with an embankment R for the passage of a transverse lane.

The number of elements 1 constituting the platform 6 is determined as a function of the width of the passage to be made, the plates 3 of the elements being provided, on their lateral sides 30, with conjugate parts engaging one inside the other of way to avoid the risks of strumming.

On the other hand, as previously, the elements 1 placed on the sides of the platform 6 thus produced, are provided with raised portions 36 forming self-formwork for the realization of the slab D by pouring concrete 1 1 until- above the level of the upper flanges 22 of the beams 2 which are thus completely embedded in the concrete 1 1.

The elements 1 forming such a platform 6 can simply be placed, at their ends, on the two abutments 61, by means of conventional supports, for example neoprene or roller supports for dilations.

However, to allow very large spans without increasing the height of the metal beams 2 excessively, it is preferable to provide a recess 60 at each end of the platform 6.

Figure 8 is a detail view showing, by way of example, such a recess.

As shown in Figure 7, the platform 6 consists of a number of elements 1 placed side by side and each comprising a concrete plate 3 in which are sealed the lower flanges 21 of several metal beams 2. However, as as shown in FIG. 8, each metal beam 2 is extended beyond the transverse edge 38 of the plate 3, by a part 23 extending over a free length d and coming to rest, via a metal grain 24, on a plate 25 sealed on the upper face 64 of the right-hand side 61. In order to prevent concrete leakage during the pouring of the slab, a seal 26 is placed along the transverse edge 38 of the plate 3 which is located substantially at the inner edge of the upper portion 63 of the pawl 61. Longitudinal irons 13 placed at the end of each beam 2 and possibly welded to the inner faces of the flanges 21, 22, are extended by waiting portions 14 in the form of hooks which intersect with irons left waiting at the end. upper end of the right-hand side 61. Other waiting irons as well as transverse irons 66 can, moreover, cross with the stand-by irons 14, 65 in order to reinforce the recess thus formed during the pouring of the concrete 11 above the contiguous elements 1 and the podium 61, the latter being provided at its upper part with a suitable formwork. The connection between the beams 2 and this recess 60 can be further improved by welding along the ends of the beams 2, several series of metal studs 27 forming connectors.

The platform 6 and recessed at its ends in the piers 61 can have a very large L3 range, up to 15 m, for a relatively small height h, of the order of 500 to 600 mm, for example.

As indicated above, the prefabricated elements according to the invention can be light enough to be handled by medium power lifting equipment and the use, as longitudinal reinforcements, of metal profiles cooperating with the concrete slab D makes it possible to reduce thickness of it. The method according to the invention is therefore particularly suitable, for example, for the coverage of an urban motorway, often made in trench, because it allows to put in a few hours, in the middle of the night, a number of prefabricated elements. placed side by side, the concrete plates 3, armed by the lower plies 4 'welded to the flanges 21 of the beams 2, being strong enough to safely achieve the casting of the concrete 1 1 forming the slab, even after the recovery of the circulation. But the invention is also particularly advantageous for the realization of mixed bridges with several spans.

The use of prefabricated elements according to the invention makes it possible, by joining together the ends of the beams 2 of two consecutive elements, to provide a platform of great length resting on one or more intermediate supports. FIG. 9 shows, by way of example, a bridge comprising such a platform 6 of great length resting on an intermediate stack 7 and, at its ends, on abutments 61.

As previously, the platform 6 shown, in partial section, in FIG. 10, consists of a number of prefabricated elements 1 comprising, according to the invention, metal beams 2 having a bottom soleplate 21 sealed in a plate. concrete 3 with a lower reinforcing ply 4 '. Preferably, the lateral elements 1a comprise a raised portion 36 which forms a self-formwork for pouring the concrete 1 1 embedding all the reinforcements to form the slab D. In the example shown, this slab D is covered with a wearing course 15 and may comprise, on each side, a sidewalk 16 and a railing 17.

The prefabricated elements 1 forming the platform 6 can have a large range, for example from 10 to 15 m, and bear at one end on the abutment 61 and at the other end on the intermediate stack 7 (Figure 1 1). Preferably, the end of the platform 6 resting on the abutment 61 forms a recess 60 made in the manner described above with reference to Figure 8, such an installation to limit the height of the beams 2 necessary to withstand the applied loads.

Figures 1 1 to 13 show the realization of the intermediate support on the stack 7, before casting the concrete constituting the slab.

FIG. 11 shows, in elevation, the junction between two consecutive elements 1, 1 'extending on either side of a transverse joint plane Q, at the level of the intermediate support 7, FIG. cross-section in the joint plane Q. Each prefabricated element 1, 1 'comprises, as in the case of FIG. 1, three metal girders 2 having a bottom flange 21 and a reinforcing ply 4' sealed in the concrete slab 3 constituting the basis of the element. However, the beams 2 are extended by a portion 23 beyond the transverse edge 38 of the plate 3 which is stopped at a distance (d) from the joint plane Q while the beams 2 extend substantially until joint plane, the ends 23, 23 'cantilever parts of the beams being separated only by a small gap (i). According to the invention, the corresponding beams 2, 2 'of two consecutive elements 1, 1' which are placed in the extension of one another, are joined together by a splice 8 comprising vertical plates 81 bolted on the webs 20, 20 'of the two beams 2, 2' and sets of horizontal plates 82, 83 bolted on the two faces, respectively inner and outer of the flanges, respectively bottom 21, and upper 22 of the two beams 2, 2 '.

In this way, the ends of each pair of beams 2, 2 'are perfectly joined together, which then works as a continuous beam.

These two beams 2, 2 'thus secured by the fishplates 8, rest on the stack 7 by means of a neoprene support 71 interposed between two metal grains centered on the joint plane Q, respectively a lower grain 72 taking support on the stack 7 and an upper grain 73 on which bear the ends of the lower flanges 21 of the two beams 2, 2 ', this grain 73 being provided with countersinks 74 for accommodating the clamping bolts of the fishplates.

After laying the elements 1, 1 'and the joining of the beams 2, 2', a lower formwork panel 75 is put in place to form the bottom of the space left free between the ends 38, 38 'of the concrete plates 3, 3 'of the two elements 1, 1'. As shown in Figure 12, each space between two consecutive elements 1, 1 'can be closed by a panel 75 in two parts provided with notches for the passage of the bearing grains 73 of the three pairs of beams 2, 2', the entire panel being sealingly attached to the transverse edges 38, 38 'of the two plates 3, 3' and to the grains 73 so as to form a formwork allowing the casting of self-placing concrete on the plates 3, 3 'of the consecutive elements to form the platform 6 by embedding all of the metal beams joined together and the two upper layers 4 which can be connected by longitudinal connecting bars 45.

Since a continuous slab is thus produced, it is also possible to shift the joint plane Q with respect to the axis of the stack 7. In this case, represented in FIG. 14, one of the elements 1 rests directly, by its concrete plate 3, on the stack 7 and the metal beams 2, 2 'of two consecutive elements are secured in pairs by means of a joint 8, made in the manner indicated above. However, the junction plane Q being offset relative to the stack, the space between the ends 38, 38 'of the plates 3, 3' of the two elements 1, 1 'can be closed simply by a shuttering panel 77 fixed on the beams by stirrups 78.

Of course, the invention is not limited to the details of the embodiments which have just been described as simple non-limiting examples and could be the subject of other variants.

Thus, to facilitate the penetration of concrete and the coating of the reinforcements of the slab, the metal beams 2 could have another profile, for example with a perforated core or lattice.

On the other hand, the width (L) of the elements 1 may vary, as well as the number of beams 2 per element and their spacing, the constitution of the secondary reinforcement 4 and the distribution of the longitudinal and transverse irons 13 and 12 being adapted accordingly. .

In addition, the prefabricated elements 1 will normally have a rectangular shape, with two lateral sides 30 parallel to the beams 2 but other forms can be envisaged. For example, some elements could have convergent lateral sides in order to make a bridge platform at an angle or in a curve.

Similarly, if the invention is particularly suitable for the realization of building floors or a mixed deck platform, other types of slabs could be made from prefabricated elements according to the invention.

Furthermore, other arrangements could be envisaged for the production of prefabricated elements according to the invention comprising a monolithic reinforcement cage made of I-section or H-section metal sections rigidly connected by two reinforcing plies.

FIG. 15 shows, by way of example, in cross-section, another embodiment of such a prefabricated element comprising three longitudinal sections 2a, 2b, 2c with an I-section, the lower flanges 21 of which are embedded in a plate made of Concrete 3. Conventionally, this concrete slab can be reinforced with a welded mesh 31 passing below the flanges 21 of the beams 2 and whose ends 31 'can be folded to arm the lateral sides 30 of the plate 3 but this lattice 31 would be insufficient to avoid, during demolding and handling of the element , the risk of cracking of the concrete plate 3 by the soles 21 embedded in it, in case of overturning, even small, metal beams 2.

According to the invention, this risk is avoided by rigidly connecting the lower flanges 21 and upper 22 of the beams by two reinforcing plies so as to produce a relatively undeformable monolithic reinforcement cage.

In the embodiment of FIG. 15, this securing of the metal beams is obtained by means of tubular cages 40a, 40b constituted by longitudinal bars 42 connected by rings 46 whose lower part and the upper part are placed respectively at the level of the soles. lower 21 and lower flanges 22 and welded thereon by welding points 47, 47 ', the rings 46 being also welded to the webs 20 of the beams 2 by welding points 48.

Each hoop 46 of a tubular cage 40 is thus connected to each of the profiles 2 which surround it, by three separated welding points 47, 48, 47 'and thus constitutes a non-deformable rectangular assembly opposing the overturning of the sections 2a, 2b.

As previously, the outer faces 23, 23 'of the flanges 22, 21 of each beam 2 are provided with connectors 24 consisting, for example, studs welded to the sole and projecting so as to ensure perfect bonding with the plate 3 and the concrete 1 1 poured on it after the installation of the element, the monolithic reinforcement cage thus produced cooperating with the concrete to withstand the forces applied. A slab D of any width can be made by placing side by side a number of prefabricated element 1 having a width of 2 m to 2.5m. FIG. 16, for example, shows a slab having a width of approximately 5 m consisting of two elements 1, 1 'placed side by side on either side of a junction plane P. The concrete plates 3, 3 'are provided, on the side opposite the plane P, cornices 36 allowing casting of the concrete 1 1 to form the slab D, a seal 35 being placed between their adjacent sides. An intermediate tubular cage 40c is placed between the end beams 2c, 2'c of the two adjacent elements 1, 1 '. This intermediate cage 40c consists, like the cages 40, of a number of longitudinal bars 42 connected by rings 46 but its thickness is reduced so as to rest on the upper face 32 'of the two adjoining plates 3, 3' by ensuring the joining of the two parts of the slab D. If necessary, to reinforce the reinforcement of the slab D, transverse threads (12) are put in place, before casting the concrete (1 1) so as to extend across the width of the platform through the souls 20 of the beams 2 by orifices previously drilled in the factory for this purpose. In the case shown in Figure 2 where cornices 36, 36 'are formed along the lateral sides 30, 30' of the slab D, these cornices can be reinforced by a suitable reinforcement not shown, so as to form side beams 36, 36 ', with, optionally, armatures waiting which provide the connection with the transverse threads 12. Similarly, the beams 2 which constitute, in the longitudinal direction, the main reinforcement of the slab D, may be supplemented by longitudinal threads 13 added to the reinforcement cages 4.

It is thus possible to make a slab more or less armed depending on the loads to bear. Furthermore, in order to produce a prefabricated element 1, by avoiding the inversion of the reinforcement cage, it is also possible to place in the mold 10 a ply of reinforcements 4 'kept at a minimum distance from the bottom of the mold by spacers, then to place on it the beams 2 whose lower flanges, provided in advance of the studs 24 ', are welded to the cross bars 41'. It is then possible to pour the concrete plate 3 and then to lay and weld the upper reinforcing ply 4 on the upper flanges 22 of the beams 2. Of course, it is also possible to lay and weld the upper ply 4 and then to pour the concrete to form the slab link 3.

Claims

1. Prefabricated element for producing a reinforced concrete slab, comprising at least two longitudinal metal beams (2) each having at least one core (20), a lower flange (21) and an upper flange (22); reinforced concrete slab (3) in which the lower flanges (21) of the metal beams (2) are embedded, and transverse connection means between the longitudinal beams (2), said concrete slab (3) constituting, after laying of the element (1) on at least two spaced apart supports (61, 7), a formwork for casting a concrete layer (1 1) in which the longitudinal beams (2) are embedded, so as to form the slab (D), characterized in that the connecting means between the longitudinal beams consist of two transverse reinforcement plies (4, 4 ') extending respectively between the lower flanges (21) and the upper flanges (22). ) of said beams (2) and rigidly fixed on them so as to form with said beams (2) a monolithic reinforcement assembly capable of withstanding the bending forces applied in the longitudinal direction and in the transverse direction cooperating with the concrete plate (3), during the transport and installation of the element (1) on its supports (61, 7).

Prefabricated element according to Claim 1, characterized in that the two reinforcing plies (4, 4 ') each comprise a plurality of spaced transverse bars (41, 41') welded to the outer faces (23, 23). ') flanges, respectively upper (22) and lower (21) longitudinal beams (2), and a plurality of longitudinal bars (42, 42') welded to said cross bars (41, 41 ').

3. Prefabricated element according to claim 1, characterized in that the two reinforcing plies respectively form, with the flanges (21, 22) of the beams (2), the lower part (4 ') and the upper part (4). ) at least one tubular reinforcement cage (40) extending between two longitudinal beams (2) substantially along their entire length and secured thereto by welding points (47, 47 ', 48) made respectively at the level of the upper flanges (22) and lower (21) and on the core (20) of the beam (2).

4. prefabricated element according to one of the preceding claims, characterized in that at least the outer faces (23, 23 ') of the flanges, respectively upper (22) and lower (21) of the longitudinal beams (2), are provided with connectors (24, 24 ') extending projecting so as to ensure the bonding of the beam with the concrete which enrobe.

5. prefabricated element according to one of the preceding claims, characterized in that the vertical core (20) of each metal beam (2) has a perforated structure having concrete passage openings on either side of the beam (2) through the vertical core (20).

6. prefabricated element according to one of the preceding claims, characterized in that the concrete plate (3) in which is embedded in the lower portion (21) of each beam (2) has a width (L) compatible with the possibilities transport by road or rail.

7. prefabricated element according to one of the preceding claims characterized in that the concrete plate (3) is extended at right angles along at least one of its lateral sides (30) by a raised portion (36). ) so as to form a cornice having a height (h) at least equal to the thickness of the wall (D) to be produced.

8. Prefabricated element according to one of the preceding claims, characterized in that the concrete plate (3) is extended at right angles along at least one of its transverse sides (38) by a raised part (56). ) forming a cornice in which is embedded the corresponding end of each longitudinal beam (2).

9. Prefabricated element according to one of the preceding claims, characterized in that, at at least one of its ends, each metal beam (2) is extended beyond the corresponding transverse side (38) of the plate ( 3), by a connecting portion (23) extending in a console and can be secured to a corresponding portion (23 ') of a metal beam (2') of a next element (1 ').

10. A method of producing a prefabricated element (1) for producing a slab (D), characterized by the following steps:

placing, on a plane support, at least two parallel metal beams (1) spaced apart from one another, each having a core (20), a first sole (22) placed on the support and a second sole (21);

- laying on the second flanges (21) of the beams (2) of a plurality of transverse bars (41) and welding thereof over the entire width of the sole (21); - laying on the transverse bars (41 ') of a plurality of longitudinal bars (42') and welding them with the transverse bars (41 ') so as to form a first reinforcing ply (4');

- Turning the assembly and laying beams (2) and the first web (4 ') on the support; - laying on the first flanges (22) of the beams (2) of a plurality of transverse bars (41) and welding thereof over the entire width of soles (22);

- laying on the transverse bars (41) and welding with them of a plurality of longitudinal bars (42) so as to form a second ply of reinforcements (4);

- producing a hollow prefabrication mold (10) having a bottom (101) substantially planar, and at least four sides, respectively two longitudinal sides (102) and two transverse sides (103);

- Establishment in the mold of the monolithic reinforcement cage consisting of longitudinal beams (2) secured by the two reinforcing plies (4, 4 '), a minimum coating distance (b) being maintained between the longitudinal bars (42 ') of the lower ply (4') and the bottom (101) of the mold (10);

casting concrete (1 1) in the mold so as to cover the bottom thereof to a thickness (e) sufficient to encompass the lower portions (21) of the metal beams (2) and the lower reinforcing ply ( 4 '),

- stripping after setting and hardening of the concrete to obtain a prefabricated element (1) comprising at least one longitudinal metal beam (2) having a bottom flange (21) and a reinforcing ply (4 ') sealed in a plate (3) of reinforced concrete capable of constituting a formwork for casting a concrete slab (D) armed by the monolithic reinforcement cage constituted by the beams (2) secured by the two plies of reinforcement (4, 4 ').

1. A method of producing a prefabricated element (1) for producing a slab (D), characterized by the following steps:

- Making a hollow prefabrication mold (10) having a substantially planar bottom, and at least four sides, respectively two longitudinal sides (102) and two transverse sides (103); - placing in the mold (10) an armor ply (4 ') consisting of longitudinal bars (42') above which transverse bars (41 ') are welded, said ply (4') being maintained spaced apart from the bottom (101) of the mold (10) by a minimum distance (b);

- laying on said ply (4 ') of at least two longitudinal metal beams (2) having a bottom flange (21), a web (20) and an upper flange (22) and welding the lower flanges (21) on the transverse bars (41 ') of the reinforcing ply (4');

- placing and welding on the upper flanges (22) of the beams (2) of a reinforcing ply (4) consisting of transverse bars (41) welded to the flanges (22) of the beams (2), on which are welded longitudinal bars (42),

- stripping after setting and hardening of the concrete to obtain a prefabricated element (1) comprising at least two longitudinal metal beams (2) having a bottom flange (21) and a reinforcing ply (4 ') sealed in a plate (3) of reinforced concrete capable of constituting a formwork for pouring a concrete slab (D) armed by the monolithic reinforcement cage constituted by the beams (2) secured by the two plies of reinforcement (4, 4 ').

12. A method of producing a reinforced concrete slab resting on at least two spaced apart supports, from at least one prefabricated element (1) made according to one of claims 10 and 1 1, characterized in that at least one prefabricated element (1) resting on at least two spaced apart supports is provided and that the plate (3) is surrounded by shuttering elements extending vertically to a height at least equal to to the thickness (h) of the slab (D) to be produced, this being obtained by pouring concrete (1 1) into the mold thus formed and whose plate (3) constitutes the bottom.

13. The method of claim 12, characterized in that, at each of the supports (53), the concrete plate (3) is provided with a recess (37) into which at least one connecting piece ( 54) provided at the desired location on the support (53) for sealing the slab (D) with the support (53), by casting concrete in said recess (37).

14. Method according to one of claims 12 and 13, characterized in that the slab (D) consists of at least two prefabricated elements (1, 1 ') placed next to each other with at minus two adjoining adjacent sides (30, 30 ') and two outer sides along which the concrete slab (3) is provided with a raised part (36) constituting a formwork element for pouring concrete (1 1) in the mold thus formed.

15. Method according to one of claims 12, 13, 14 characterized in that the slab (D) consists of at least two elements (1, 1 ') placed one after the other in the longitudinal direction, with joining of the adjacent ends (23, 23 ') of the metal beams (2).