EP0342090A1 - Prestressed semi-finished concrete element and production equipment - Google Patents

Abstract

Prestressed semi-finished concrete building element, comprising prestressing cables (14-1 to 14-n) embedded in a concrete slab (12) of small thickness and additionally comprising a wire mesh (16) having a central sheet resting on the prestressing cables and embedded in the concrete slab, and also two raised edges (21-1, 21-2) extending perpendicularly to the sheet and parallel to the prestressing cables, these two edges projecting from the concrete slab to form prepared reinforcements, at least one sunk block (36, 38) being partly embedded in the concrete of the slab, thus permitting the formation of a lightweight building element. The invention also relates to production equipment for such a building element. <IMAGE>

Description

The invention relates to a prestressed concrete construction element, of the pre-slab type, as well as an installation for its manufacture.

Construction elements are already known, of the pre-slab type, comprising a thin concrete plate or slab in which are pre-stressed cables generally laid in sheet form.

These are prefabricated surface elements suitable for use as lost formwork, in particular for the manufacture of floors. Such a construction element is first placed in its final location on site and then receives a layer of concrete called a "compression table" which, after hardening, forms with this element a resistant slab of greater thickness.

It has also been proposed to lighten a building element of this kind by providing, for example, a block or a sheet of expanded polystyrene which is disposed on the building element before casting the compression table.

This solution requires the provision of complex reinforcement which must be tied to the prestressing cables and arranged so as to form waiting reinforcements to facilitate the mechanical anchoring of the compression table on the building element itself.

The installation of this reinforcement, which takes place before pouring the concrete of the building element, is long and delicate to carry out and does not lend itself to automated manufacturing on modern installations comprising prestressing benches.

It is therefore an object of the invention to provide a building element, of the pre-slab type, which does not have the drawbacks of known building elements.

It is also an object of the invention to provide such a construction element of the lightened type.

It is also an object of the invention to provide such a construction element which can be easily manufactured on a prestressing bench.

It is another object of the invention to provide an installation for the manufacture of such a building element.

The prestressed concrete construction element of the invention is of the type comprising prestressing cables embedded in a thin concrete plate.

According to an essential characteristic of the invention, this element further comprises a wire mesh having a central ply resting on the prestressing cables and embedded in the concrete plate as well as two raised edges extending perpendicular to the ply and parallel to the cables prestressing, these two raised edges projecting from the concrete plate to form waiting reinforcements, at least one lost block of light material being partially embedded in the concrete of the plate in the space between the two raised edges, which makes it possible to form a lighter construction element.

By the expression "partially embedded in the concrete of the plate", it is meant to specify that the or each lost block is partially embedded in the concrete of the plate, for example to a depth of the order of a millimeter, this which allows a kind of bonding of the or each block on the concrete plate.

When then, concrete is poured on the construction element to form a compression table, this table is bound to the construction element thanks to the raised edges of the trellis forming the waiting reinforcement.

In a preferred embodiment of the invention, the building element comprises two spaced lost blocks, which makes it possible to obtain two lateral locations for lateral concrete ribs in the respective regions of the two raised edges of the trellis and a location central for a central concrete rib, extending parallel to the two lateral locations.

These two lateral ribs and this central rib will be formed subsequently by the concrete of the compression table in the regions corresponding respectively to the two lateral locations and to the aforementioned lateral location.

In such a case, the invention provides that the building element comprises, at each of the two ends of the central location, a frame, for example in the form of a sinusoid, which is anchored to the trellis and which is partly embedded in the concrete of the plate to form a waiting reinforcement.

This last reinforcement also contributes to the connection of the building element and the compression table which is associated with it.

The wire mesh used in the manufacture of the building element comprises longitudinal wires arranged parallel to the prestressing cables and transverse wires welded to the longitudinal wires, the transverse wires being bent at right angles in the vicinity of their two ends, at the level d 'a longitudinal wire, to form the two raised edges of the trellis.

In another aspect, the invention relates to an installation for manufacturing such a building element, this installation comprising a prestressing bench having a manufacturing area and means for tensioning prestressing cables.

According to the invention, this installation further comprises a folding machine capable of moving along the bench to fold, at right angles, the two longitudinal edges of the welded mesh previously arranged flat on the prestressed cables under tension.

Advantageously, the folder comprises a rolling gantry capable of moving over the entire length of the manufacturing area, this gantry comprising a lifting frame capable of being interposed between the prestressing cables and the trellis, two folding flaps carried by the gantry and each pivotally mounted about an axis parallel to the direction of movement of the gantry, between a low position where the flap is disposed under an edge of the trellis and a high position where the edge of the trellis has been raised under the action of the shutter, as well as means of actuating the shutters according to an alternating pivoting movement and means for moving the gantry.

• - la figure 1 est une vue en perspective d'un élément de construction selon l'invention ;
• - la figure 2 est une vue en coupe transversale de l'élé­ment de la figure 1 ;
• - la figure 3 est une vue de dessus de l'élément de la figure 1 ;
• - la figure 4 est une vue en perspective montrant l'an­crage d'une armature en forme de sinusoïde sur les fils transversaux du treillis ;
• - la figure 5 est une vue en perspective montrant la structure du treillis ;
• - les figures 6,7 et 8 montrent différentes phases de mise en place d'un feuillard sur l'aire de fabrication d'un banc de précontrainte ;
• - la figure 9 est une vue latérale d'une plieuse propre à être utilisée dans une installation à banc de précon­trainte ;
• - la figure 10 est une vue en coupe suivant la ligne X-X de la figure 9 ; et
• - la figure 11 est une vue en perspective éclatée d'une partie de la plieuse des figures 9 et 10.

In the description which follows, given solely by way of example, reference is made to the appended drawings, in which:

• - Figure 1 is a perspective view of a building element according to the invention;
• - Figure 2 is a cross-sectional view of the element of Figure 1;
• - Figure 3 is a top view of the element of Figure 1;
• - Figure 4 is a perspective view showing the anchoring of a sinusoidal frame on the transverse son of the trellis;
• - Figure 5 is a perspective view showing the structure of the trellis;
• - Figures 6,7 and 8 show different phases of fitting a strip on the manufacturing area of a prestressing bench;
• - Figure 9 is a side view of a folder suitable for use in a prestressed bench installation;
• - Figure 10 is a sectional view along line XX of Figure 9; and
• - Figure 11 is an exploded perspective view of a part of the folder in Figures 9 and 10.

The building element 10, of the pre-slab type, shown in FIGS. 1 to 3 comprises a concrete plate 12 in which are embedded a multiplicity of prestressing cables 14-1,14-2, ..., 14-n, arranged in sheet form, the cables being parallel to each other and to the direction of prestressing. For example, the plate 12 can have a running width of 1.20 m or more, a thickness of 4 to 5 cm and a length of up to 6 m.

The element 10 further comprises a wire mesh 16 which best appears in FIG. 5, comprising longitudinal wires 18-1,18-2,18-3,18-4 and 18-5 on which transverse wires are welded 20-1,20-2,20-3, ..., 20-n. The wire mesh 16 is disposed on the prestressing cables 14-1 to n, before pouring the concrete intended to form the plate 12, this mesh being arranged so that the longitudinal wires 18-1 to 18-5 are parallel to the prestressing cables. The two lateral edges of the trellis 16 are bent at right angles to the longitudinal wires 18-2 and 18-4 to form two raised edges 21-1 and 21-2 which thus connect to a central ply 22, the latter being formed by the central part of the transverse wires 20-1,20-2, ... and extending laterally to the longitudinal wires 18-2 and 18-4. After pouring the concrete from the plate 12, the central ply 22 is embedded in the concrete, while the raised edges 21-1 and 21-2 protrude from the concrete upwards, extending parallel to the direction of prestressing and perpendicular to the central ply 22 of the trellis 16.

The plate 12 comprises, in the example, two chamfers 24-1 and 24-2 which are connected respectively to two vertical edges 26-1 and 26-2 (Figures 1,2 and 5). These edges and these chamfers are obtained by edge rules arranged on a manufacturing bench, in a manner known per se.

The plate is further limited by two vertical end edges 28 and 30 extending perpendicular to the prestressing cables, and by a lower surface 32 and an upper surface 34.

After pouring the concrete forming the plate 12, while this concrete is still fresh, there are on the surface 34 of the concrete two blocks 36 and 38 in lost material, for example in expanded polystyrene, and this between the two raised edges 21-1 and 21-2 of the trellis, a space being provided between these two blocks. These two blocks have a rectangular section and can have, for example, a thickness of the order of 10 cm. These blocks are, in part, embedded in the concrete of the plate 12 using, for example, a vibration table which has just been applied to the respective upper surfaces 40 and 42 of the blocks 36, 38. This vibration table ensures, on the one hand, the insertion of the blocks 36 and 38 into the concrete to a depth which can be of the order of a millimeter and, on the other hand, the leveling of the blocks 36 and 38.

Thus, after the concrete has hardened, these blocks are integral with the plate 12. Two lateral locations 44-1 and 44-2 are thus formed in the respective regions of the edges 20-1 and 20-2 and a central location 46 s' extending parallel to the lateral locations 44-1 and 44-2, in the limited space between the blocks 36 and 38. At the two ends of the central location, two frames 48 and 50 are provided respectively, in the example in the form of a sinusoid, which are anchored to the trellis 16 and are thus partially embedded in the concrete to form waiting reinforcements. As shown in Figure 4, the frame 48 comprises sinusoids which pass respectively under the transverse son 20-1,20-2, etc., of the trellis 16 and are tied to the latter. It is the same for the frame 50.

The building element 10 is intended to be used as lost formwork to form in particular a floor. When the element 10 is thus used on site, concrete is then poured onto this element to form a compression table which comes to bind to the element 10 thanks to the waiting reinforcements formed by the raised edges 21-1 and 21- 2 of the trellis and by the end frames 48 and 50. Due to the presence of the blocks 36 and 38, a lightened composite element of greater thickness is thus obtained. The lateral locations 44-1 and 44-2 and the central location 46 are then filled with the concrete of the compression table to form concrete ribs.

The raised edges 21-1 and 21-2 resist the shearing force after pouring the compression table, in particular at the resumption of concreting pre-slab-compression table, and this over the entire length of the element of construction.

The frames 48 and 50 extend over a length corresponding to the calculation of the shearing force (approximately 40 cm for a pre-slab of 4.50 m in length, stressed under house loads). The frames 48 and 50 can also be used for handling the building element until it is used on site.

The manufacturing of a construction element 10 according to the invention can be carried out by means of a prestressing bench installation, as described for example in French patent application n ° 85-04947 filed on April 1, 1985 in the name of the plaintiff.

It will be recalled here that such an installation essentially comprises a horizontal manufacturing area, extending over a width of approximately 1.50 m and over a length of several tens of meters, for example 100 m or more . Such an installation also comprises means suitable for placing and tensioning prestressing cables above the manufacturing area. Furthermore, this installation includes means for distributing and vibrating concrete on the manufacturing area, the prestressing cables being tensioned above this area.

It may be advantageous, in certain cases, as shown in FIGS. 6 to 8, to recover the used civil engineering decking from the bench by unrolling a strip 52 on the bench. The process then consists of unrolling and stretching the strip along the bench on the civil engineering so as to obtain a perfect surface condition. The strip 52 consists of a metal strip, presented in the form of a roll 54, having a width corresponding to that of the bench and a thickness of the order of 2 to 3 mm, for example. This strip is placed on the bench 56 and one end 58 is folded and welded of the strip on one end 60 of the bench. The strip is then unwound over the entire length of the bench (Figure 6). The strip is then cut off and its other end 62 (FIG. 7) is tensioned by means of two jacks 64 by means of a header 66 bolted into the end 62 of the strip. Then we welds the strip by plug welds 67 at the opposite end of the bench 56 (FIG. 7) and the end 62 is folded down as shown in FIG. 8.

Of course, this operation of fitting a strip is only to be provided in the case of a used bench which needs to be repaired.

In an installation of the type defined above, the invention provides a folder 70 which will now be described with reference to FIGS. 9 to 11.

The folding machine 70 is intended to move along the manufacturing area to fold at a right angle the two edges of the trellis 16 previously laid flat and stretched over the prestressed cables tensioned, so as to form the two raised edges of the trellis.

The folder 70 comprises a gantry 72 provided with four wheels 74 capable of moving on two rails 76 arranged on either side of the manufacturing area and over the entire length of the latter. The gantry 72 comprises two cross members 80 on which depend two longitudinal beams 82 spaced apart from each other, each of the two beams 82 supporting two wheels 74.

On each of the beams 82 depend a multiplicity of arms 84 which extend horizontally towards the inside of the gantry and which carry pivots 86 aligned in a horizontal direction parallel to the direction of movement of the gantry on the rails 76. These pivots 86 serve on the one hand to the removable mounting of a lifting frame 88 and on the other hand to pivot with two folding flaps 90.

The chassis 88 comprises a multiplicity of crosspieces 92 connected together by longitudinal elements 94, each crosspiece 92 carrying, at each of its ends, a pin 96 suitable for being engaged in a pivot 86. The flaps 90, which each have a shape twisted or veiled, also have a multiplicity of pins 98 suitable for cooperating with the pivots 86.

From the two cross members 80 depends, by means of four supports 100, a form of support 102 comprising a multiplicity of longitudinal bars 104 supported by two cross members 106, these two cross members being connected, at their two ends, to two supports 108 to wedge-shaped section extending parallel to the direction of travel of the gantry.

Each of the flaps 90 can be subjected to an alternating pivoting movement by means of a jack 110 whose rod 112 is articulated on the central part of a lever 114. One of the ends of the lever 114 is articulated at 116 on a beam 82 and its opposite end carries a sphere 118 suitable for engaging in a gutter 120 formed on the external surface 122 of the corresponding flap 90. When the rod 112 of the jack is retracted, the flap 90 is in a low position and, when this rod is deployed, the flap gradually pivots to approach the corresponding support 108 and raise an edge of the trellis held captive between the flap and the corresponding support.

On the articulation 124 between the rod 112 and the lever 114 is also articulated a rod 126 carrying a rack 128 which cooperates with a freewheel pinion 130 of one of the wheels 74. Consequently, each time that the rod of the jack is deployed, the corresponding component swivels from the low position to the high position and the gantry also moves by a corresponding step. When the cylinder rod is retracted, the flap returns to its low position but the gantry does not move due to the freewheel drive.

At the front of the gantry 72, two rollers 132 are provided which are suitable for respectively guiding the longitudinal wires 18-2 and 18-4 of the welded mesh, as well as two body washers 134 suitable for promoting the lifting of the mesh. The gantry also supports a generator of pressurized fluid 136 supplying the two jacks 110.

The installation, as shown, is used as follows.

First of all, there is a layer of prestressing cables 14-1 to 14-n above the manufacturing area which is put under tension. Next, there is, above these cables, the wire mesh 16 which is stretched by subjecting it to a lower tension than that of the prestressing cables. For this, one acts only on the longitudinal wires 18-2, 18-3 and 18-4 of the trellis by calling, for example, on the traction beam of the prestressing bench. The tension exerted on the wires 18-2, 18-3 and 18-4 must not be too high so as to be able to raise the trellis by means of the lifting frame 88 of the folder 70.

We start by placing the chassis 88, which is removable, under the welded mesh and above the prestressing cables. We then engage the folder, after having slightly folded the two lateral feeders of the welded mesh, and we pin the frame 88 under the frame 72 by means pivots 86. It is then ensured that the longitudinal wires 18-2 and 18-4 of the trellis engage in the input rollers 132 which serve as guides (FIG. 9). The folding of the two edges of the trellis is then carried out sequentially according to an adjustable pitch over the stroke of the jacks. As the folding machine moves in the direction of arrow F (Figure 9), the welded mesh, initially flat, is folded on its two edges. At each movement step, the two flaps 90 fold the edges of the mesh in the direction of the supports 108 as shown in Figure 10. As can be seen in Figures 10 and 11, each support 108 has a support surface 138 which is slightly inclined to the vertical. In this way, the flap 90 ensures the folding of the corresponding edge, for example 21-1 (Figure 10), to a position P (shown in dotted lines in Figure 10) which is located beyond the vertical. In this way, by the very elasticity of the lattice, the raised edge then returns to a substantially vertical position, that is to say at right angles to the central ply of the lattice. As also shown in FIG. 10, there is a clearance d between the folded edge of the chassis and the flap, which then makes it possible to unhook the chassis 88 and consequently to release the folder from the folded welded mesh. After this operation, the chassis is then removed laterally from below the welded mesh.

Following these operations, the welded mesh is folded over its edges while being correctly centered relative to the manufacturing area. It then suffices to have the reinforcements 48 and 50 in the form of a sinusoid and to proceed with the pouring of the concrete, as described for example in the aforementioned French patent application No. 85-04947.

When the concrete is still fresh, there are, for each element 10, two lost blocks 36 and 38 which are penetrated and leveled in the fresh concrete using appropriate vibration means.

After the concrete has hardened, the blocks 36 and 38 are joined to the concrete plate thus formed and the construction element obtained can be transported to its site of use.

Claims (10)

1. - Prestressed concrete construction element, of the pre-slab type, comprising prestressing cables (14-1 to 14-n), embedded in a thin concrete plate (12), characterized in that it comprises in addition to a wire mesh (16) having a central ply (22) resting on the prestressing cables and embedded in the concrete plate, as well as two raised edges (21-1,21-2) extending perpendicular to the ply and parallel to the prestressing cables, these two raised edges projecting from the concrete plate to form waiting reinforcements and in that at least one lost block (36, 38) of light material is partly embedded in the concrete of the plate in the space between the two raised edges, which makes it possible to form a lightweight construction element. 2. - building element according to claim 1, characterized in that it comprises two lost blocks (36,38) spaced, which allows to obtain two lateral locations (44-1,44-2) for ribs concrete in the respective regions of the raised edges (21-1,21-2) of the trellis and a central location (46) for a concrete rib extending parallel to the two lateral locations. 3. - building element according to claim 2, characterized in that it comprises, at each of the two ends of the central location (46), a frame (48.50) for example in the form of a sinusoid, which is anchored in the trellis (16) and which is partly embedded in the concrete to form a waiting reinforcement. 4. - construction element according to one of claims 1 to 3, characterized in that the wire mesh (16) comprises longitudinal wires (18-1 to 18-5) arranged parallel to the prestressing cables (14-1 to 14-n) and transverse wires (20-1 to 20-n) welded to the longitudinal wires, the transverse wires being bent at right angles near their ends, at the level of a longitudinal wire (18-2,18- 4), to form the two raised edges of the trellis. 5. - Installation for manufacturing a building element according to one of claims 1 to 4, comprising a prestressing bench having a manufacturing area (56) and means for tensioning prestressing cables, characterized in that that it further comprises a folder (70) adapted to move along the bench to fold at right angles the two longitudinal edges of the wire mesh (16) disposed flat on the prestressed cables under tension. 6. - Installation according to claim 5, characterized in that the folder (70) comprises a rolling gantry (72) adapted to move over the entire length of the manufacturing area, this gantry comprising a lifting frame (88) suitable for being inserted between the prestressing cables and the trellis, two folding flaps (90) carried by the gantry and each pivotally mounted around an axis (86) parallel to the direction of movement of the gantry, between a low position where the shutter is arranged under an edge of the trellis and a high position where the edge of the trellis has been raised under the action of the shutter as well as means (110, 112, 114) for actuating the shutters, according to an alternating pivoting movement and means ( 74,126,128) of displacement of the gantry. 7. - Installation according to claim 6, characterized in that the lifting frame (88) is removably mounted on the gantry by means of pins (96) which cooperate with pivots (86) also serving for the pivoting of the flaps. 8. - Installation according to one of claims 6 and 7, characterized in that the shutter actuating means comprise, for each shutter (90), a lever (114) mu by means of a jack (110 ) and able to move the shutter between its two positions, a support (108) depending on the gantry being provided to cooperate with the shutter in its high position. 9. - Installation according to claim 8, characterized in that the jack (110) also acts on the wheels (74) of the gantry to advance it in successive steps, each step corresponding to a pivoting cycle of the flap. 10. - Installation according to one of claims 5 to 9, characterized in that each flap (90) has a veiled or twisted shape.

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