FR2833285A1 - Fixing system for lifting rings in pre-stressed concrete slab with cells consists of fitting rings in cells and holding in place by passive rods - Google Patents

Abstract

The system for fixing lifting rings (4) in a pre-stressed concrete slab (1) with cells (5) consists of piercing the base of a cell after pouring the concrete but before it has set, inserting a ring through the cell so that its lower end is just above the slab moulding surface (10), and inserting a passive rod (6) into the wet concrete so that it passes through the ring just below the level of the pre-stressing rods (2). The cell is then filled with concrete to hold the ring in place, leaving the upper end of the ring exposed in a cavity (7) in the slab surface.

Description

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 The present invention relates to the problems posed by the installation of lifting means, such as rings, in a prestressed alveolar concrete slab.

 It is known to manufacture prestressed concrete slabs by pouring concrete onto tensioned wires and to have gripping means, such as rings, pins or the like when casting concrete, in order to be able to lift these slabs by lifting devices (cranes, industrial trucks or others).

 According to the regulations in force, and this in order to avoid accidents, the lifting rings, or the like, must concern the reinforcement wires; in such a way that these lifting means cannot be torn off from the slab during the lifting operation of the latter.

 For full slabs, it is easy to arrange the lifting rings by surrounding them with the wires; but this is very delicate with the honeycombed slabs because the said rings will move, during the pouring of the concrete.

 The object of the present invention is to solve these various problems.

 The method according to the present invention consists in placing an iron in support below at least two prestressing wires, this iron passing through a lifting ring; so that any tensile force exerted on the ring is transmitted by said iron to the prestressing wires.

 Preferably, this iron is arranged perpendicular to the prestressing wires and has a length such that it is located below a plurality of prestressing wires (at least two).

By way of nonlimiting examples and to facilitate understanding of the invention, the accompanying drawings show: - Figure 1 a cross-sectional view of a prestressed slab according to the present invention.

- Figure 2 a sectional view along AA of Figure 1.

- Figure 3 a view corresponding to Figure 2 of a first alternative embodiment.

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 - Figure 4 a view corresponding to Figures 2 and 3 of a third embodiment of the invention.

 Referring to these figures, it can be seen that the slab 1 is a pre-stressed slab by means of pre-stressed wires 2 and has cells 3.

 The prestressing wires, to be taken from the mass of the concrete, pass by the cells 3.

 According to the technique currently used, the prestressing wires 2 are made of steel, but the invention is not limited to this particular case.

 To install the lifting ring 4; while the slab 1 has just been poured, we pierce the bottom of a cell 3 and we put in place a ring 4 so that its lower end is slightly (1 to 2 cm) above the tray. casting, but below the plane containing the prestressing wires.

 The bar 6 is then introduced by forcing it into the mass of the poured concrete, ensuring that the upper wall of this bar 6 passes just below the prestressing irons 2.

 The recess in which the ring 4 is located is then filled with a mass of concrete 5 in order to block the ring 4 in position.

 The height of the ring 4 can be such that its upper end projects slightly above the upper wall of the slab. Wood blocks being placed between each slab when they are superimposed in the storage area, the upper part of said rings must protrude by a length less than that of the height of said blocks.

 But according to a variant, shown in the figures, the cell is not completely filled with the concrete 5; so as to provide an empty space 7 in which the upper end of the ring 4 protrudes, which allows it to be hung on a lifting device, in this case it is necessary that the length of the ring 4 is less to the thickness of the slab 1.

 Figures 3 and 4 show two alternative embodiments. In these figures the same elements bear the same references.

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 In Figure 2 we see that the ring 4 instead of being a closed ring is constituted by a pin.

 In FIG. 4, it can be seen that the ring 4b is not either a closed ring like the ring 4 but a U-shaped iron, the two ends of which are folded upwards and outwards so that it is possible to put two passive steels 6 under the strands 2.

 In all the examples shown, the bar 6 is a passive iron, in the sense that it does not participate in prestressing, moreover it can be provided with a pointed end in order to better sink, by force, into the concrete. which has just been sunk.

Claims (10)

1. Method for installing lifting means (4) in pre-stressed concrete slabs (1), provided with cells (5), characterized by the fact that each lifting means (4,4a, 4b) is fixed ) in a cell (5) by means of a passive iron (6) which is placed below the sheet of prestressing wires (2).  2. Method according to claim 1, according to which the following successive steps are carried out: a). The bottom of a cell (5) is drilled just after pouring, before setting the concrete. b). A lifting means (4,4a, 4b) is placed in said cell, its lower end being slightly above the casting plate (10). vs). A passive iron (6) is forced into the mass of poured concrete, at a level situated slightly below the layer of prestressing wires (2). d). The cell (5) is filled in with concrete to lock the lifting means in position (4,4a, 4b) 3. Method according to claim 2, wherein the upper end of the lifting means (4,4a, 4b) protrudes above the upper face of the slab (1) by a length less than the thickness of the shims spacers arranged between the tiles when stacked on top of each other.  4. Method according to claim 2, wherein the length of the lifting means (4,4a, 4b) is less than the thickness of the slab (1) so that an empty space (7) is left in the part high of the cell so that the end of the lifting means (4,4a, 4b) protrudes from the blocking concrete, without protruding above the upper face of the slab (1).  5. Slab (1) in prestressed concrete, provided with cells, manufactured according to the method of claims 1 and 2.  6. Slab (1) in prestressed concrete according to claim 5 in which a passive iron (6) is wedged between the lower part of a lifting means (4,4a, 4b) and the underside of the sheet of prestressed wires (2).  7. Slab manufactured according to the method according to claim 4, wherein the lifting means is a closed ring (4). <Desc / Clms Page number 5>  8. Slab manufactured according to the method according to claim 4, wherein the lifting means is a pin (4a).  9. Slab manufactured according to the method according to claim 4, wherein the lifting means (4b) is a U-shaped iron folded at its two ends so that it can be crossed by two passive irons (6).  10. Slab according to any one of claims 5,6, 7, wherein the length of the lifting means (4,4a, 4b) is less than the thickness of the slab (1).