DESCRIPTION

Metal joint allowing expansion and transfer of vertical loads between adjacent concrete slabs

This invention concerns a metal expansion joint between concrete slabs and in particular, slabs for industrial floors.

To create large concrete surfaces, the area is divided into square or rectangular sections constituting the concrete slabs. These concrete slabs are demarcated using metal profiles constituting the expansion joint between the slabs.

These joints are designed to allow variations in the dimensions of the slabs, mainly due to shrinkage following hardening of the concrete after pouring, and to thermal variations.

The joints must also be able to withstand stress due to heavy loads and maintain the concrete slabs at the correct horizontal level. Special care must be taken to avoid damaging the edges of the concrete slabs in contact with the metal joint.

To this effect, several types of joint have already been proposed as described in documents WO 2005/1 1 1307 and EP 0 953 682. In order to take account of the cost of raw materials and in particular the price of steel, it has been suggested that the metal joints be made from simple steel sheet instead of hot or cold laminated profiles. This would significantly reduce the weight and consequently the price of the metal joints.

Such a joint is described in Belgian patent no. 2004/0379. The joint for concrete slabs is made from a vertical sheet fitted, at around mid-height and at regular intervals, with a series of pegs or metal plates which extend horizontally either side of the vertical sheet. These plates transfer vertical load or stress to the metal joint, and also keep the slabs levels. To this effect, the plate which extends into one of the slabs is fitted with a sleeve before the concrete is poured, such that this sleeve becomes integral with this slab whilst allowing the plate that it contains to move in a horizontal plane.

This type of joint is wholly satisfactory but its fabrication requires a great deal of manpower due to the cuts to be made in the steel sheet at regular intervals and the subsequent welding of plates in each cut-out. The aim of the present invention is to rectify the disadvantages cited above by simple and effective means.

This aim is achieved in that the metal joint is made from a single main sheet, which is cut and bent such that it serves as the median separator sheet and also forms the plates that transfer the vertical load charges between the two slabs, these plates being obtained by appropriate bending of the said main sheet.

The essential characteristics of the invention are described in the appended claims.

Other elements of the invention will be described in detail below, using a example embodiment and referring to the appended diagrams in which:

Figure 1 is a cross section of the joint according to the invention;

Figures 2 to 5 are views showing the embodiment of the single main sheet, constituting the joint according to the invention; Figure 6 is an exploded perspective view of the joint in accordance with figure 1.

Figure 7 is a view similar to figure 1 , showing a cross section of the joint following movement, in the horizontal plane, of the two adjacent slabs.

According to figures 1 and 6, the metal joint 10, situated between two edges of slabs 1 and 2, is made essentially from a single principal longitudinal sheet 3 , positioned according to a vertical median line L, of which the upper end constitutes the upper edge of concrete slab 1 and of which the lower end has longitudinal sections bent at an angle of 90° either side of the median line L.

Between the sections which are bent at right angles on either side of the median line, the lower part of the main sheet 3 is held vertically over the whole of its original width. Thus a profile is obtained, formed by a single main sheet

3 of which the upper part extends vertically over the whole of its length and of which the lower part is constituted by vertical sections 4 separating the horizontal sections bent alternately towards the interior of slab 1 (sections 5) and the exterior of slab 1 (sections 6). Sections 6 intended to work in conjunction with the adjacent slab 2 are fitted with sheaths 7 before the concrete is poured to allow limited movement of the slabs in a horizontal direction.

Sections 5, bent towards the interior of slab 1 , are fitted with openings 8 allowing adequate anchorage between the concrete slab and the horizontal sections 5 of the vertical main sheet 3.

The horizontal sections 5 and 6 thus constitute load transfer surfaces between the adjacent concrete slabs 1 and 2. It is generally acknowledged that the load transfer surfaces are situated at approximately mid-height of the concrete slabs. Depending on the slab height envisaged, the main sheet 3 must be extended downwards by a secondary sheet 9, which is thinner than the main sheet 3. The width of sheet 9 then depends on the thickness of the concrete slabs.

Along the upper lateral section of the main sheet 3 there is usually a series of pins 1 1 , which anchor this part of the metal joint into the hardened concrete.

Main sheet 3 and secondary sheet 9 therefore constitute the lateral extremity of slab 1 and form an integral part of this slab with the aid of the pins 1 1 and the openings 8 in sections 5.

The essential element of the metal joint 10, the subj ect matter of the invention, is thus constituted by the main sheet 3, with the horizontal sections 5 and 6, the vertical sections 4, the pins 1 1 and

the secondary sheet 9 extending downwards to the lower extremity of the slabs. These parts 3 , 4, 5, 6, 1 1 and 9 form an integral part of the concrete slab 1.

As shown in figure 1 , the upper edge of slab 2 is fitted with a flat bar 13, which also has a series of pins 12 anchoring the flat bar 13 into the concrete of slab 2. Before the concrete is poured either side of the metal joint 10, the flat bar is fitted along the upper edge of the single main sheet 3 using bolts (not shown), which pass through the oblong openings 14 provided at regular intervals along the upper edge of sheet 3 and the flat bar 13. To allow for shrinkage of the concrete slabs, these bolts (or just the nut) are made of plastic so that they can break during the usual shrinkage of concrete when it is solidifying.

From this moment, any lateral movement of the concrete slabs becomes possible, given that the main sheet 3, the secondary sheet 9 and the cut sections 4, 5 and 6 remain integral with slab 1 , and that the flat bar 13 and the sheath 7 remain integral with slab 2 as illustrated in figure 7.

In the event of major stresses on slabs 1 and 2, the loads transmitted downwards will be taken up by the horizontal sections 5 and 6 and by the basement.

Figures 2 to 5 show an example of the manufacturing process for the principal sheet 3.

Figure 2 shows an end of a sheet 3 , which can for example be 12,5 cm wide and 300 cm long. The thickness of the main sheet 3 shall preferably be about or superior to 5 mm in order to secure the rigidity of the joint structure before pouring the concrete and to absorb the transfer of important vertical charges applied to the surface of the concrete slabs. The lower side is indented at predetermined intervals by saw (or laser) cuts 15 in order to form sections 4, 5 and 6. At the same time, the openings 8 and the oblong holes 14 can be made.

In the second manufacturing phase, shown in figure 3, sections 5 and 6 are bent alternately either side of the median line of sheet 3 at right angles (90°). Vertical sections 4 are left intact.

Figures 4 and 5 show respectively an outline sketch and a front elevation of the profile thus obtained and it is easy to see the significant advantage of the manufacturing process for the metal joint in relation to the state of the art. The most important advantages of the joint, subject of the present invention, are as follows:

- substantial limitation of the quantity of steel necessary to manufacture the single main sheet of the joint, lowering the cost of the primary material needed and the total weight of the joint structure; - limitation of the number of separate components of the joint resulting in substantially less welding operations lowering the total amount of labour costs;

- achievement of adequate upper edge protecting means for the adjacent concrete slabs; - achieving adequate supporting means for the transfer of important vertical loading charges at mid-height of the slabs resulting in a metal joint suitable to support very important charges up to 50 tons/metre according to tests performed with such metal joints;

- offering the possibility to pour the two adj acent concrete slabs at the same time, resulting in a substantial time saving operation with respect to the existing methods (pouring of the second concrete slab only when the first is completely solid).

Of course, the metal joint such as described and illustrated in the present description is only an example embodiment and other forms or models of elements are possible without straying outside the framework of the present invention.