Patent Publication Number: US-8112959-B2

Title: Device connecting concrete slabs at an expansion joint

Description:
FIELD OF THE INVENTION 
     The present invention is related to the construction field, in particular to the production of concrete slabs for example used as industrial floors, and to the devices that equip the joints between parts of slabs. 
     In this description, the word “joint” is used exclusively to denote the zone or space between two adjacent slabs while, in the area of construction, this term is generally used to refer to the device itself which occupies such a zone. 
     STATE OF THE ART 
     The problems associated with joints between slabs are well known in the construction field. The device that equips them must be able to fulfil one or advantageously several functions:
         absorb dimensional variations due to shrinkage and temperature differences;   support heavy loads, leaving the slabs level;   protect the slab edges in the upper part;   reduce the lift of the slab edges following differential shrinkage in the thickness.       

     Originally, joints were equipped with sliding dowels, but the difficulty of placing the dowels perfectly parallel is such that the method is currently avoided. 
     In general, joints are equipped with a continuously folded, double metal profile at mid-height of the slab, possibly forming an assembly of the mortise-and-tenon type or leaving space for a continuous flat metal element. This type of profile has the great drawback of reducing the strength of the slab near the joint, since it cuts the joint continuously at mid-height: only one half of the slab withstands heavy loads. In addition, to produce angled joint junctions is particularly tricky and requires a great deal of labour. 
     Other profiles have therefore been developed. These are devices composed of two juxtaposed profiles equipped at regular spacings with flat dowels passing through the joint in one and the same horizontal plane, one end of which is anchored in the slab on one side of the joint while the other end has the possibility of sliding in a sheath embedded in the slab on the other side of the joint. However, this device, although already more effective, does not provide a solution to the lift of the slab edges since it may be likened to an articulation. 
     Document US2004/0107661 presents another device, composed of two metal plates folded at right angles, a horizontal part of which is placed beneath the slab and a vertical part is flush with the surface of the slab. This solution is advantageous from a strength standpoint, but it is very expensive to manufacture because of the amount of steel used, and it has several installation difficulties since the form of the foundation must be set perfectly level before the device is put into place. 
     AIMS OF THE INVENTION 
     The aim of the present invention is to produce a device for equipping joints in slabs, which is inexpensive to produce, easy to implement and fulfils the functions expected of it, without having the disadvantages of the current prior art. 
     SUMMARY OF THE INVENTION 
     The invention is related to devices as described in the appended claims. 
     According to a first embodiment, the invention is related to a device composed of two profiles which fit together, one in the other, by discontinuous bracket-shaped projections in order to ensure continuity in a slab in line with a joint while still permitting movements in the horizontal plane and protecting the slab edges, but opposing any lift and differential transverse movements. 
     According to a second embodiment, the invention is related to a device consisting of a profile, one part of which is bent up alternately in one direction and then in the other, to which any second profile is joined, being temporarily fastened to the first. Certain bent-up parts pass through the joint and are provided with a sheath in order to allow free movement in all directions in the plane of the slab. The two profiles are each anchored in a slab part separated by the joint. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  represents a side view of a device according to a first embodiment of the invention. 
         FIG. 2  illustrates the operation of the device shown in  FIG. 1 . 
         FIG. 3  represents a perspective view of the device of  FIG. 1 . 
         FIG. 4  represents a further modification of the device of  FIG. 1 . 
         FIG. 5  represents a side view of a device according to a second embodiment of the invention. 
         FIG. 6  represents an alternative version of the device according to the second embodiment. 
         FIG. 7  represents an further alternative version of the device according to the second embodiment. 
         FIG. 8  represents a perspective view of the device of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 to 4  show a device according to a first embodiment of the invention. This first embodiment is characterized by the design of the device in the sense that it is made up of two profiles that fit together in such a way that the elements passing through the joint between the slabs are discontinuous and have in fact a bracket shape anchored by dowel anchors. This configuration has the particular feature of being likened to an embodiment. 
       FIG. 1  gives an example of the device according to the first embodiment. Placed in the joint separating two slabs  1  and  2  is a device composed of two profiles  3  and  4 , preferably made of metal, each placed vertically and anchored in the slab on one side of the joint by means of anchoring dowels  5   a ,  5   b . Certain parts  6   a ,  6   b  of the profiles  3  and  4  have been bent up at discrete places in order to pass through the joint  7  and the other profile in order to extend into the other slab. The device is such that the bent-up projections  6   a , 6   b  are alternately in one slab then in the other slab on each side of the joint  7 . A sheath  8  placed over this bent-up projection allows the latter to move in all directions in the plane of the slab, but independently of the latter. The sheath  8  is necessary for a good operation of the device, but it is not necessarily a part of the device as such. It can be attached in a temporary way to the profiles, or simply placed over the projections before the device is installed. 
     The anchoring dowels  5   a , 5   b  may be plate dowel anchors. The dowels are fixed to an upstanding portion of each profile and extend outwards from the profile without crossing the joint. This way, the dowels are arranged for anchoring the first and second profile in the slab on the respective side of the joint. 
       FIG. 2  explains one feature of the device. When a load is applied to the slab  2 , said load is transmitted to the projection  6   a  of the profile  3 , and anchored in the slab  1  by means of the dowel  5   a  lying in another plane of the slab  1 . In this way, a reaction occurs in the form of a tension/compression pair  9 - 10  which makes it possible to balance a moment. This is therefore an embodiment capable of reducing the lift of the slab edges. 
       FIG. 3  shows the discontinuous character of the device. The bent-up projections  6   a , 6   b  integral with the profiles  3  and  4  are disposed, alternately in one slab and the other, on either side of the joint  7 . 
     Referring once more to  FIGS. 1 to 3 , it is seen on these figures that each profile is constituted by a series of essentially square brackets, connected by vertical portions of the profile. A bracket of the left-hand profile  3  is formed by an upstanding portion  20   a  and by a bent-up projection  6   a  of the profile  3 . A bracket of the right-hand profile  4  is formed by an upstanding portion  20   b  and a bent-up projection  6   b . Brackets of the same profile are connected by vertical portions  21   a ,  21   b  (FIG.  3 —portions of profile  4 , between vertical dotted lines). Openings  22  are present in the profiles. The openings  22  of one profile  3 , 4  serve to let the bent-up projections of the other profile pass from one side of the joint  7  to the other side. Preferably, the device is installed in such a way that the bent-up projections  6   a ,  6   b  are situated approximately in the middle of the height of the slab. When the height of the device does not correspond to the height of the slab, a thin plate  13  is installed underneath the device, to close off the joint. 
       FIG. 4  shows another arrangement according to the first embodiment of the invention. The profiles  3  and  4  are reinforced at the top by profiles  11  and  12  of larger cross section. The dowels  5   a , 5   b  may have any shape. In general, the geometry of the elements does not modify the features of the invention. Also in the embodiment of  FIG. 1 , the anchoring dowels  5   a , 5   b  may be anchoring elements of any suitable shape or size. 
     The characterizing elements of the first embodiment of the invention are the following: a device composed of two profiles which fit together, one in the other, by discontinuous bracket-shaped projections in order to ensure continuity in a slab in line with a joint while still permitting movements in the horizontal plane and protecting the slab edges, but opposing any lift and differential transverse movements. 
       FIGS. 5 to 8  show a device according to a second embodiment of the invention. The second embodiment of the invention is characterized by the design of the device in the sense that it is made up of a single profile, the lower part of which is bent alternately in one slab part and the other on each side of the joint. This profile is anchored by anchoring dowels in just one slab and provides protection of the concrete edge on only one side of the joint. The concrete edge on the other side of the joint is protected by a second profile, which is temporarily fixed to the first. 
       FIG. 5  gives an example of the device according to the second embodiment of the invention. Placed in the joint separating two slabs  101  and  102  is a device composed of a profile  130  and another, smaller, profile  131 , both preferably being made of metal, each placed vertically and anchored in the slab on one side of the joint  107  by means of anchoring dowels  132   a ,  132   b . The lower part of the first profile  130  is divided into segments which are bent up alternately, to form bent-up projections  133   a ,  133   b  in the two slabs  101  and  102 . A sheath  135  is placed over the projections passing through the joint  107 , thereby allowing said projections to move in all directions in the plane of the slab, but independently of the latter. A thinner piece  136  is placed beneath the device in order to close off the joint. The parts  135  and  136  are not a part of the device as such. They are necessary for good operation of the device. The sheaths  135  may be attached in a temporary way to the profile, or simply placed over the projections before the device is installed. 
       FIG. 6  shows another arrangement according to the second embodiment. The profile  130  is supplemented at the top with an element  137  of different cross section. The profile  131  of  FIG. 5  is then replaced with a profile  138 , the upper face of which is similar to that of the profile  137 . The anchoring dowels  132  may have any shape. In general, the geometry of the elements does not modify the features of the invention—the elements  137  and  138  could be replaced with angle sections or other profiles without reducing the scope of the invention. Elements  137  and  138  are not necessarily similar in size or shape. 
       FIG. 7  shows another arrangement according to the second embodiment of the invention. The lower part of the profile  130  is divided into segments, some of which  133   a ,  133   b  are bent up to form bent-up projections alternately in the slabs  101  and  102 , but others  140  are left directed downwards in order to serve as support for the thinner piece  136  that closes off the joint. 
       FIG. 8  shows the perspective view of the device according to the second embodiment, already shown in  FIG. 5  and indicates the various constituent elements of the device. The drawing represents the invention with a single segment folded up alternately in one direction  133   a  and then in the other  133   b , but this embodiment does not limit the scope—there could be several successive segments bent in the same direction, or even without a form of alternation. 
     As seen on  FIG. 8 , the device according to the second invention is built up of square bracket shaped portions, consisting of a bent-up projection  133   a  or  133   b  and an upstanding portion of the profile  130 . 
     The characterizing elements of the second embodiment of the invention are the following: a device consisting of a profile, one part of which is bent up alternately in one direction and then in the other, to which any second profile is joined, being temporarily fastened to the first. Certain bent-up parts pass through the joint and are provided with a sheath in order to allow free movement in all directions in the plane of the slab. The two profiles are each anchored in a slab part separated by the joint. The reference to a temporary or provisional connection is explained in more detail hereafter: in the assembled device, the profile  131  or  138  is attached to the main profile  130  by a provisional attachment means such as bolts, clips or other adequate means, i.e. these profiles are not necessarily firmly attached e.g. by welding, but are fixed together with sufficiently strong attachment means to allow the device to be installed easily.