WO2008090260A1

WO2008090260A1 - Method and apparatus for providing reinforced construction joint in concrete structure

Info

Publication number: WO2008090260A1
Application number: PCT/FI2008/050022
Authority: WO
Inventors: Jorma Kinnunen
Original assignee: Peikko Group Oy
Priority date: 2007-01-23
Filing date: 2008-01-22
Publication date: 2008-07-31
Also published as: EP2122076A1; FI20075045A0; FI20075045L

Abstract

A method and an apparatus for providing a reinforced construction joint in a concrete structure, in which method a dowel-like countersink is provided in a concrete surface by means of a case-like structure (3). In the case-like structure (3) there is arranged a cable sling (4) whose first end is anchored to the cast concrete and the second end is prevented from adhering to the concrete structure. The case-like structure (3) is removed from the concrete structure after hardening of concrete and the second end of the cable sling (4) is straightened substantially perpendicular to the bottom surface of the dowel-like countersink. The case-like structure (3) is formed of one integral piece whose surface facing the interior of the concrete structure is provided with a recess (7) for the second end of the cable sling (4). The recess is provided with protrusions (8) that are arranged to keep the second end of the cable sling (4) in place in the recess and to allow the case-like structure (3) to be removed from the concrete.

Description

METHOD AND APPARATUS FOR PROVIDING REINFORCED CONSTRUCTION JOINT IN CONCRETE STRUCTURE

[0001] The invention relates to a method for providing a reinforced construction joint in a concrete structure, in which method a substantially dowel-like countersink is provided in a concrete surface by means of a case- like structure, in which case-like structure there is arranged a cable sling whose first end is anchored to the cast concrete and a second end is prevented from adhering to the concrete structure, and in which method the case- like structure is removed from the concrete structure after the concrete is hardened and the second end of the cable sling is straightened to be substantially perpendicular to the bottom surface of the dowel-like countersink. The invention also relates to an apparatus for providing a reinforced construction joint in a concrete structure.

[0002] The above described methods and apparatuses have been known in the field for several years. The cast-in-situ reinforced concrete structures are divided by means of construction joints into suitable casting entities. In horizontal joints of the structures the reinforcement may rise freely above the upper edge of the formwork. In the above-mentioned situation the reinforcement continues with an overlapping joint to an upper casting portion. In vertical joints the reinforcement is conventionally brought through the formwork edge. Previously formwork was provided with holes for extensions of ribbed steel bars in order to provide a functional reinforcement on both sides of the construction joint. Protruding ribbed steel bars, which are often sharp at cut-off points, make working difficult at the construction joint. It is very cumbersome, however, to remove the casting formwork provided with holes and to clean the joint after hardening of the concrete.

[0003] In order to eliminate the drawbacks of the prior art a large number of solutions, which are based on case-like structures, have been developed in the field. These solutions employ case-like structures that are arranged in the edge of a piece to be cast. Inside the case-like structure there is arranged a cable sling which serves as an anchor and whose one end is anchored in the concrete to be cast. An example of this solution is described in PCT publication WO 98/03751. This solution employs a case-like part at the bottom of which there is a hole through which is applied an end of the cable sling to be anchored in the concrete. The case-like part remains permanently in the concrete structure. [0004] A drawback with the above-described structure is that of the structure is cumbersome to install, in other words, it is a difficult operation to apply the cable sling through the hole, etc. A further drawback is high material consumption, because the case-like structure is for single use.

[0005] To eliminate the drawbacks of the above-mentioned solutions there is developed a solution in which the case-like structure is removed from the concrete structure, whereby the costs caused by single use of the case-like structure will be eliminated. An example of these solutions is described in Fl patent application 20021678.

[0006] A drawback with the structure described in Fl patent application 20021678 is its complexity, in other words, a case-like structure comprises a plurality of separate parts, which increases the manufacturing costs. A further drawback is that the case cover is difficult to remove, because only a smooth surface of the cover is visible after casting of the concrete structure, and therefore it is difficult to get hold of the cover for its removal. Yet another drawback is that the case-like structure is difficult to remove. The side plates of the case have a bevel, which makes the removal easier. Nevertheless, the end plates of the case-like structure are perpendicular to the surface of the concrete structure, and consequently said surfaces adhere to the concrete and removal is difficult. Moreover, the amount of work required to refill the case-like structure also poses a drawback. Because the case-like structure comprises many parts, it takes many work steps to fill it: cleaning of the case of concrete residues, if any; application of a new cable sling through a hole to the bottom and bending it under the side walls of the case; insertion of a cover pin to a hole in the end plate and setting of a cover seal between the loop in the cable sling. The above-mentioned details increase costs and consequently the result is not the best possible.

[0007] The object of the invention is to provide a method and an apparatus by which the drawbacks of prior art will be eliminated. This is achieved by the method and the apparatus of in accordance with the invention. The method of the invention is characterized in that the case-like structure is formed of one integral piece, whose surface facing the interior of the concrete structure is provided with an open recess, not extending to a surface facing outwardly from the concrete structure, for the second end of the cable sling and that the recess is provided with protrusions that keep the second end of the cable sling arranged in the recess in place in the recess and allow the case-like structure to be removed from the concrete by preventing concrete from packing around the cable sling. The apparatus of the invention, in turn, is characterized in that the case-like structure is formed of one integral piece, whose surface facing the interior of the concrete structure is provided with an open recess, not extending to a surface facing outwardly from the concrete structure, for the second end of the cable sling and that the recess is provided with protrusions that are arranged to keep the second end of the cable sling arranged in the recess in place in the recess and to allow the case-like structure to be removed from the concrete by preventing concrete from packing around the cable sling.

[0008] A primary advantage of the invention is its simplicity: the structure consisting of one piece is advantageous both to manufacture and to use. Installation is advantageous, because problems arising from several separate parts will be eliminated, in other words, refill of the case-like structure comprises fewer work steps than refill using prior art technology. In addition, cumbersome application of the cable sling through the hole is omitted completely. There will not arise problems associated with sealing of the hole, because the apparatus of the invention does not comprise a hole. A further advantage of the invention is that removal of the case-like structure is an easy and fast operation, because it is easy to get hold of the structure with a tool and because the shape of the case-like structure on all sides contributes to the removal.

[0009] In the following, the invention will be described in greater detail by means of an example appearing in the attached drawings, in which

Figure 1 is a schematic side view of a precast concrete element provided with apparatuses of the invention,

Figure 2 is a top view of the element in Figure 1 ,

Figure 3 a schematic perspective view of the element in Figures 1 and 2,

Figure 4 is a schematic perspective view of the element in Figure 3 with the case-like structures being removed and the cable slings turned outwardly,

Figure 5 is a schematic side view of a construction joint that has been provided by means of two elements shown in Figure 4,

Figure 6 is a top view of the structure in Figure 5,

Figure 7 is a schematic side view of the apparatus of the invention, Figure 8 is a top view of the structure in Figure 7,

Figure 9 is a front view of the structure in Figure 7,

Figure 10 is a rear view of the structure in Figure 7,

Figure 11 is a schematic perspective view of the structures in Figures 7 to 10 and

Figure 12 is a schematic perspective view of the structures in Figures 7 to 10 seen from another direction.

[0010] Figures 1 to 3 show a schematic view of a concrete element, which is manufactured by utilizing the method of the invention and in which the apparatus of the invention is used. In Figures 1 to 3, reference numeral 1 denotes the concrete element, and correspondingly, reference numeral 2 denotes the apparatus of the invention. A case-like structure, which constitutes an essential part of the apparatus 2, is denoted by reference numeral 3. A cable sling, whose first end is anchored to concrete, is denoted by reference numeral 4. Three apparatuses are used in the example of Figures 1 to 3. It is obvious that the number of apparatuses 2 may vary in accordance with the size of the concrete element 1.

[0011] The object of the method and apparatus of the invention is to provide a reinforced construction joint in a concrete structure. Figure 4 shows a perspective view of the precast concrete element 1 of Figures 1 to 3, from which the case-like structures 3 constituting part of the apparatus 2 have been removed, and consequently a dowel-like countersink 5 provided by means of the case-like structure 3 is visible. In Figure 4, second end of the cable sling 4 is straightened to be in a protruding position, in which it is substantially perpendicular to the bottom surface of the dowel-like countersink 5.

[0012] Figures 5 and 6 show a schematic view of a reinforced construction joint provided between two concrete elements 1 for instance in accordance with those shown in Figure 4. As appears from Figures 5 and 6, the cable slings 4 straightened to a protruding position are set to overlap such that a reinforcement element 6 may be inserted through the slings.

[0013] Figures 7 to 12 show the apparatus of the invention. In Figures 7 to 12, like reference numerals refer to like parts as in Figures 1 to 6.

[0014] In accordance with the basic idea of the invention the case- like structure 3 consists of one integral piece. That appears clearly from Figures 7 to 12. Thus, the case-like structure 3 has no separate bottom and cover. Therefore, it takes fewer work steps to refill the case-like structure, i.e. to ar- range the cable sling to be supported by the case-like structure, than in the prior art. The case-like structure forms a dowel in the edge of the concrete element, which dowel transfers the shearing force in the construction joint between the elements. The case-like structure 3 is removable after hardening of concrete and reusable, whereby the drawbacks associated with the single use of some prior art solutions will be eliminated.

[0015] On the rear surface of the case-like structure, i.e. on the surface facing the interior of the concrete structure in installation, there is provided an open recess 7 for a second end of the cable sling 4. It appears clearly from Figures 7 to 12 that the case-like structure 3 is substantially open for the surface facing the interior of the concrete structure, in other words, the recess provided for the second end of the cable sling opens to the surface of the case-like structure 3. The first end of the cable sling 4 is anchored to the cast concrete as stated above. As it can be seen in the figures, the open recess 7 does not extend through the case-like structure 3, i.e. there is no hole for the cable sling through the case-like structure.

[0016] As it can be seen in Figures 7 to 12, the second end of the cable sling remains in the rear surface of the case-like structure, i.e. in the surface facing the interior of the concrete element, such that the upper surface of the second end of the sling is substantially on the level of the edges of the case-like structure and also visible on said surface. When arranged in the case-like structure the second end of the cable sling is not inserted inside the case-like structure, as is the case in prior art multiple-use solutions referred to, but it remains visible on the surface of the substantially case-like structure 3. These details appear from Figure 7. As stated above the case-like structure 3 does not comprise a hole or a groove to be sealed, through which the end of the cable sling would enter in the case-like structure.

[0017] The recess 7 provided in the rear surface of the case-like structure 3 is designed such that the second end of the cable sling 4 will lock into place in the recess. The recess comprises protrusions 8, through which the second end of the cable sling is guided into the recess 7. The protrusions 8 press on the surface of the second end of the cable sling 4 which is on the level of the rear surface of the substantially case-like structure. The protrusions extend to at least part of the surface of the second end of the cable sling 4, seen in the longitudinal direction of the cable, i.e. the protrusions 8 press on the cable surface for at least part of the length of the cable sling in the recess. In addition, the protrusions 8 press against the surface of the cable sling arranged in the recess for at least part of the surface as the visible outer surface of the cable is seen in the direction of the cross-sectional circumference of the cable.

[0018] The second end of the cable sling 4 is quick to mount on the case-like structure, because there is no need to insert the cable through a small hole. The loop of the second end of the cable sling also tends to expand, because the cable resists tight bends, and therefore the second end locks very efficiently behind the protrusions as shown in Figures 10 and 11.

[0019] When a reusable case-like structure is used, it is essential that the case-like structure is easily detachable from the concrete after hardening of cast concrete. In the invention the detachment of the case-like structure 3 is made easier by means of protrusions 8. As described above, the cable is arranged behind the protrusions 8, whereby the protrusions 8 prevent concrete from packing around the cable sling.

[0020] The recess provided in the rear surface of the case-like structure 3 includes alternatives for various sling lengths, whereby the same case-like structure is applicable for joints of different sizes. Consequently, there is no need to manufacture and store case-like structures of different sizes, but one case-like structure will suffice. Within the bottom area of different sling alternatives there is no protrusion in order for the case-like structure to be easily removed after the hardening of the cast concrete. If there were protrusions also in the bottom area of the sling, concrete would flow behind the protrusion in the empty portion of the recess and prevent the case from being removed.

[0021] In addition the protrusions 8 also serve in an advantageous manner when the case-like structure is removed from concrete. Because the protrusions 8, seen from the edge to the interior of the concrete element, are located behind the cable, the protrusions 8 pull the cable off the concrete at the same time as the case-like structure 3 is removed.

[0022] The front surface of the case-like structure 3, i.e. the surface facing outwardly from the concrete element, may be advantageously provided with a counterpart surface 9 for a tool to be used in removal. The counterpart surface 9 may be a recess, for instance, and the tool to be used may be a hammer or a crowbar, for instance. [0023] All edge surfaces of the case-like structure 3 are bevelled, whereby the case-like structure 3 is easily detachable from concrete. The bevelled edges appear clearly, for instance, in Figures 7 and 8.

[0024] When removing the case-like structure 3 the sling part arranged in the case-like structure is detached therewith. Said sling part is also straightened after removal of the case-like structure, because the sling part is bent at small radius in the case-like structure.

[0025] The case-like structure 3 may be made of any suitable material, for instance, plastic, rubber etc. It is essential that the material is sufficiently strong for multiple use.

[0026] The above described application example is not intended to restrict the invention in any way, but the invention may be modified fully freely within the scope of the claims. For instance, various details of the case-like structure may be designed in manners different from those presented in the figures etc.

Claims

1. A method for providing a reinforced construction joint in a concrete structure, in which method a substantially dowel-like countersink (5) is provided in a concrete surface by means of a case-like structure (3), in which case-like structure (3) there is arranged a cable sling (4) whose first end is anchored to the cast concrete and a second end is prevented from adhering to the concrete structure, and in which method the case-like structure (3) is removed from the concrete structure after the concrete is hardened and the second end of the cable sling (4) is straightened to be substantially perpendicular to the bottom surface of the dowel-like countersink (5), characterized in that the case-like structure (3) is formed of one integral piece, whose surface facing the interior of the concrete structure is provided with an open recess (7), not extending to a surface facing outwardly from the concrete structure, for the second end of the cable sling (4) and that the recess is provided with protrusions (8) that keep the second end of the cable sling (4) arranged in the recess in place in the recess and allow the case-like structure (3) to be removed from the concrete by preventing concrete from packing around the cable sling.

2. The method of claim ^characterized in that in the surface of the case-like structure (3) facing outwardly from the concrete structure there is provided a counterpart surface (9) for a tool to be used in removal.

3. The method of claim ^ characterized in that all edges of the case-like structure (3) are formed into bevelled surfaces.

4. The method of claim ^characterized in that the recess (7) is provided to suit for cable slings of various lengths.

5. An apparatus for providing a reinforced construction joint in a concrete structure, the apparatus intended for being mounted in a concrete surface of a concrete structure by providing a substantially dowel-like countersink (5) using a case-like structure (3), by means of which there is arranged in the structure a cable sling (4), whose first end is arranged to anchor to the cast concrete and the second end is prevented from adhering to the concrete structure, whereby the case-like structure (3) is arranged for being removed from the concrete structure after hardening of concrete and the second end of the cable sling (4) is arranged for being straightened substantially perpendicular to the bottom surface of the dowel-like countersink (5), characterized in that the case-like structure (3) is formed of one integral piece, whose surface facing the interior of the concrete structure is provided with an open recess (7), not extending to a surface facing outwardly from the concrete structure, for the second end of the cable sling (4) and that the recess is provided with protrusions (8) that are arranged to keep the second end of the cable sling (4) arranged in the recess in place in the recess and to allow the case-like structure (3) to be removed from the concrete by preventing concrete from packing around the cable sling.

6. The apparatus of claim 5, characterized in that the surface of the case-like structure (3) facing outwardly from the concrete structure is provided with a counterpart surface (9) for a tool to be used for removal.

7. The apparatus of claim 5, characterized in that all edges of the case-like structure (3) are formed into bevelled surfaces.

8. The apparatus of claim 5, characterized in that the recess (7) is provided to suit for cable slings of various lengths.

9. The apparatus of claim 5, characterized in that the protrusions (8) are arranged to press onto the surface of the cable sling arranged in the recess (7), which surface faces outwardly from bottom surface of the recess in the area that forms at least part of the longitudinal area of the cable sling.

10. The apparatus of claim 9, characterized in that the protrusions (8) are arranged to press at least partly against the surface of the cable sling arranged in the recess for at least part of the surface, as the visible outer surface of the cable is seen in the direction of the cross-sectional circumference of the cable.

11. The apparatus of claim 5, characterized in that the recess (7) is arranged to suit for cable slings of various lengths and that bottom areas of the cable slings of various lengths in the recess (7) are without protrusions.