Improvements in cantilevered coupling of a precast concrete slab to a concrete building element

Abstract

A compound coupling for cantilevered coupling of a precast concrete slab, in particular a balcony, a parapet, a canopy or a walkway, to a concrete building element, in particular a storey floor or wall element. The compound coupling includes a set of cooperating building-sided and slab-sided coupling parts that in use are anchored in and / or supported on facing end portions of the concrete slab and the concrete building element respectively, wherein the compound coupling includes at least one concrete insert piece that is to be cast into an end portion of the concrete slab or concrete building element.

Description

[0001] The invention generally relates to improvements in coupling of concrete slabs to concrete building elements of buildings. More specifically, the invention relates to improvement in cantilevered coupling of a concrete slab, in particular a precast concrete slab for e.g. a balcony, a parapet, a canopy or a walkway, to a concrete building element, e.g. a storey floor or wall element of a building. Such concrete building elements may be precast or cast in situ.

[0002] Precast concrete slabs are typically manufactured in a factory, and are transported to the building site. At the building site they may be connected to the concrete building element shortly after the concrete building element has been put into place, or later - e.g. when all floors of a building have been put up and the facade of the building is to be completed. Precast concrete slabs of a balcony, a parapet, a canopy or a walkway are typically connected to freely protrude from the facade of a building. The prefabricated concrete slabs for such cantilevered connection are typically placed without support, e.g. without temporary scaffolding. The prefabricated concrete slabs are normally hoisted into place using a crane, and are cantileveredly coupled to the concrete building element using a compound coupling acting between facing head surfaces of the concrete slab and the concrete building element respectively. The compound coupling may be embodied as a mechanical coupling, i.e. a coupling that relies on mechanical engagement of parts only to provide at least an initial load bearing connection between the concrete slab and the concrete building element. The compound coupling typically includes a tension coupling section forming an upper part of the compound coupling, and a compression coupling section forming a lower part of the compound coupling. The tension coupling section is a section of the compound coupling where tension forces are transmitted between the concrete slab and the concrete building element, and is typically located at the level of the top half of the concrete slab. The compression coupling section is a section of the compound coupling where compression forces are transmitted between the concrete slab and the concrete building element and is typically located at the level of the lower half of the concrete slab. The coupling sections may include building-sided and slab-sided coupling section parts, which each may comprise of several pieces. The coupling section parts may be coupled to reinforcement elements of the building element, and may be cast into the building element and slab respectively. The compound coupling may be arranged to improve thermal insulation between the concrete slab and the concrete building element, e.g. by including a thermal insulation body into a gap between the facing head surfaces of the concrete slab and the concrete building element that is provided by the compound coupling, and by using steel elements of low thermal conductivity in coupling section parts that traverse the gap. An example of such compound coupling is applicant's EP 0 750 076.

[0003] Although quite satisfactory in many aspects, the efficiency of coupling may be improved, e.g. in terms of manufacturing pieces of the compound coupling itself, of manufacturing of the concrete building element and the precast concrete slab with the coupling section parts, and of the process of preparing the precast concrete slab and the concrete building element for coupling, and coupling them together. In particular, at least some pieces of the compound coupling are relatively complex and costly to manufacture, complicate the formwork for the precast concrete slab and concrete building element, and complicate preparing the precast concrete slab and the concrete building element for coupling, and coupling them together.

[0004] The invention aims to provide for an improved coupling with which one or more of the above disadvantages can be ameliorated. Thereto the invention provides for a compound coupling for cantilevered coupling of a precast concrete slab, in particular a balcony, a parapet, a canopy or a walkway, to a concrete building element, in particular a storey floor or wall element, the compound coupling including a set of cooperating building-sided and slab-sided coupling parts that in use are anchored in and / or supported on facing end portions of the concrete slab and the concrete building element respectively, wherein the compound coupling includes at least one concrete insert piece that is to be cast into an end portion of the concrete slab or concrete building element. By providing the compound coupling with an insert piece that is to be cast into an end portion of the concrete slab or concrete building element, the interaction between the concrete slab or concrete building element with the coupling pieces can be facilitated, and cost of manufacture can be reduced. In particular, positioning and / or embedding the coupling pieces can be carried out with more efficiency and more precision, and transfer of forces between coupling pieces and the concrete slab and / or concrete building element can be better controlled and improved.

[0005] Within this context, a concrete insert piece is meant to be construed as an insert piece that includes concrete, preferably that is substantially or wholly made of concrete. By arranging the concrete insert piece as a prefabricated part that is to be inserted into the formwork during casting, and is to be embedded in the concrete of the slab or building element, the quality of critical parts of the coupling and / or the concrete slab or concrete building element can be chosen to be relatively high, and can be controlled well. The concrete insert piece may still include a casing, reinforcements and / or other parts made of another material. The concrete insert piece may itself be cast from concrete, but may also be at least partially machined.

[0006] Within this context, concrete is meant to be construed as a pourable, hardenable or self-hardening, mineral-bonded material, including mortar. Preferably, the concrete of the insert piece comprises High Performance Concrete (HPC), most preferably Ultra High Performance Concrete (UHPC). This way, at the location of the coupling piece, the capacity of the concrete to transfer force between coupling pieces and the concrete slab and / or concrete building element, in particular the pressure resistance of the concrete, can be chosen to be high at critical locations, while at other locations where such capacity is less critical, other aspects of the concrete can e.g. be optimized, e.g. suitability for in situ casting at suboptimal conditions, or costs. In particular, the pressure resistance of the concrete of the insert piece may be higher than the pressure resistance of the precast concrete slab or the concrete building element it is to be cast into, preferably by at least 30 MPa, more preferably by at least 50 MPa Suitable types of HPC or UHPC include self compacting concrete, reactive powder concrete, fibre-reinforced concrete or any combination thereof. Within this context, HPC may be defined to have a concrete compression strength of at least 80 MPa, and UHPC may be defined to have a concrete compression strength of at least 120 MPa.

[0007] The concrete insert piece may be configured to be a component of a coupling part, but may alternatively or in addition be configured to support a coupling part. By configuring the concrete insert piece to form at least a part of a head surface of an end portion of the precast concrete slab or the concrete building element that it is to be cast into, casting of the concrete slab or the concrete building element can be facilitated. In particular, the concrete insert piece may be configured to form an edge section of an end portion of the precast concrete slab or the concrete building element it is to be cast into.

[0008] The concrete insert piece may comprise two or more concrete modules. The concrete insert piece may be divided up into several modules. By building the concrete insert piece up from several modules, its construction can be facilitated, and its configuration can easily be adapted to different uses, e.g. different slab heights.

[0009] The compound coupling may include a tension coupling section that in use forms an upper part of the compound coupling, the tension coupling section including a set of cooperating building-sided and slab-sided tension section parts that in use are anchored to facing end portions of the concrete slab and the concrete building element respectively, and that, when cooperating, extend from one end portion to the other, in particular to traverse a gap between a head surface of the concrete slab and the head surface of the concrete building element. In particular for such type of compound coupling, the concrete insert piece may form part of the tension coupling section, in particular of the building-sided and / or slab-sided tension section parts, and more in particular of a portion of such tension section part that in use is anchored to an end portion of the concrete slab or concrete building element.

[0010] The insert piece may include a block that forms a section of the edge portion, particular a corner piece, and may be configured to form a portion of the head surface and / or a top surface of the precast concrete slab or the concrete building element it is to be cast into. This allows the formwork for the concrete slab or concrete building element to be relatively simple, and allows critical edge or corner portions of the concrete slab or concrete building element to be of controlled quality.

[0011] The concrete insert piece may be part of one of a slab- or building sided coupling part of a tension coupling section, and may comprise an anchoring block with one or more predefined holes for passing one or more tension elements of the other of a slab- or building sided coupling part of a tension coupling section therethrough. The tension elements may e.g. comprise one or more tension bars, and may e.g. include a threaded section that is secured to the anchoring block with nuts, while optionally including washers and / or plates to transfer a tension load as a compressive load on the anchoring block. The anchoring block may then transfer the load to the surrounding concrete of the concrete building element and / or the concrete slab. The holes in the concrete insert element may comprise pass through holes, but may alternatively or in addition comprise blind holes, e.g. blind holes that are provided with a threaded insert or clamp.

[0012] The concrete insert piece may be part of one of a slab- or building sided coupling part of a tension coupling section, and may comprise an anchoring block with one or more anchoring elements extending therefrom to anchor the anchoring block in the concrete of the precast concrete slab or the concrete building element that it is to be cast into. Suitable anchoring elements include e.g. rods, bars, loops or bolts.

[0013] The concrete insert piece may be provided with a removable spacer element for forming a cavity in the concrete of the precast concrete slab or the concrete building element that it is to be cast into, e.g. to facilitate forming a cavity behind an anchoring block to provide space for the ends of the tension elements to protrude through apertures in the anchoring block, and to provide space for placement and tightening of nuts.

[0014] The compression coupling may include a compression coupling section that in use forms a lower part of the compound coupling, the compression coupling including a pressure body that is configured to be arranged in the gap between the head surface of the concrete slab and the head surface of the concrete storey floor. In particular for such type of compound coupling, the concrete insert piece may form part of the compression coupling section, in particular of the building-sided and / or slab-sided compression section parts, and more in particular of a portion of such compression section part that in use absorbs and distributes pressure of the pressure body. The pressure body of the compression coupling may efficiently be embodied as a concrete pressure body.

[0015] Within this context, a concrete pressure body is meant to be construed as a pressure body that includes concrete, preferably that is made substantially or wholly made of concrete. The pressure body may itself be cast from concrete, but may also be at least partially formed in a machining operation, e.g. milling or turning. The pressure body may include casing, e.g. a plastic tube. Preferably, the concrete of the pressure body comprises High Performance Concrete (HPC), more preferably Ultra High Performance Concrete (UHPC). This way the pressure resistance of the concrete pressure body can be chosen to be high. In particular, the pressure resistance of the concrete of the pressure body may be higher than the pressure resistance of the precast concrete slab or the concrete building element it is to be cast into, and e.g. equal to the pressure resistance of the concrete insert piece.

[0016] The concrete insert piece may be configured to support the pressure body. It may e.g. include a recess to receive an end face of the pressure body or intermediate elements that the pressure body presses on.

[0017] The concrete insert piece may be arranged as a pressure distribution plate. Such concrete pressure distribution plate may form one piece with a concrete anchor block as discussed above, and may e.g. be cast in a two-step process with a cast-in reinforcement that connects the two pieces. Alternatively, the two pieces may be separate, or connected with glue to facilitate installation in the formwork. Advantageously, such two pieces may form two modules that together extend over the height of the concrete slab or the concrete building element to be formed. This way, the location and height position of the tension and compression parts of the coupling in the formwork can be controlled relatively easily, and the configuration of the edge of the formwork can be kept simple.

[0018] The concrete insert piece that is arranged as a pressure distribution plate may form an edge section of an end portion of the precast concrete slab or the concrete building element it is to be cast into, and an outer surface of the insert piece may be configured to in use form part of the head surface of the concrete slab or the concrete building element onto which the pressure body is supported, either directly or indirectly.

[0019] Transmission of compressive forces and shear forces by the compound coupling may e.g. be carried out by a pressure body that, in addition to transferring compressive forces, can also transfer shear forces. Such pressure body may e.g. be embodied as a pressure body that has relatively large dimensions in height direction, and / or that may e.g. be engaged in a form-fit closed and / or force-fit with the head surfaces of one or both of the concrete slab and / or concrete building element. In such embodiment, the pressure body integrally serves as a stiffening diagonal. As an alternative, a separate stiffening diagonal may be provided in addition to a pressure body. The pressure body may then have relatively small dimensions in height direction, and may thus be of moderate height.

[0020] The compound coupling may comprise a stiffening diagonal having a central bracket part that extends obliquely between an attachment part that is arranged to be attached to the head surface of the concrete building element of the building and a support part that is arranged to support the concrete slab and that in use is located lower than the attachment part. Such stiffening diagonal may advantageously be embodied as disclosed in Dutch patent application No. 2036530 in the name of applicant.

[0021] The pressure body may be arranged with a head surface that is arranged for cooperation with the support part of the stiffening diagonal and a tail surface that is arranged for cooperation with the head surface of the concrete building element, in particular a portion of the surface that forms part of the concrete insert piece. The pressure body may in use be enclosed in a gap between the support part of the stiffening diagonal and the head surface of the concrete building element. The stiffening diagonal may be arranged to be detachably connected to the concrete building element, e.g. by bolt connection, preferably to the concrete insert piece, more preferably to the concrete insert piece as discussed above.

[0022] The invention also relates to a precast concrete slab, in particular a balcony, a parapet, a canopy or a walkway, or concrete building element, in particular a storey floor or wall element, including a compound coupling including one or more of any of the features discussed above.

[0023] The invention further relates to a method of casting a concrete slab, in particular a balcony, a parapet, a canopy or a walkway, or concrete building element, in particular a storey floor or wall element, more in particular a concrete slab or a concrete building element as mentioned above, in which method a concrete insert piece of a compound coupling including a compound coupling that includes one or more of any of the features discussed above is included in the formwork to be embedded in the concrete of the slab or building element to be cast.

[0024] The invention still further relates to a building comprising a facade and at least one concrete building element, in particular a storey floor or wall element, to which at least one precast concrete slab, in particular a balcony, a parapet, a canopy or a walkway, has been cantileveredly coupled via a compound coupling that includes a concrete precast element including one or more of any of the features discussed above.

[0025] The above aspects of the invention individually alleviate disadvantages, and in combination can alleviate disadvantages further. The above aspects of the invention together form an invention, but may each individually also be seen as inventions on their own.

[0026] The invention will be further explained on the basis of exemplary embodiments which are represented in the drawings. The exemplary embodiments are given by way of non-limitative illustrations of the invention.

[0027] In the drawings: Fig. 1 shows a schematic side view of a first exemplary embodiment of a compound coupling with concrete insert piece that cantileveredly couples a precast concrete slab of a balcony to an in situ cast concrete building element formed by a storey floor; Fig. 2 shows a schematic side view of a second exemplary embodiment of a compound coupling with differently configured concrete insert piece that cantileveredly couples a precast concrete slab of a balcony to an in situ cast concrete building element formed by a storey floor; Fig. 3 shows a schematic side view of a third exemplary embodiment of a compound coupling with yet another differently configured concrete insert piece that cantileveredly couples a precast concrete slab of a balcony to an in situ cast concrete building element formed by a storey floor, and Fig. 4 shows a perspective view of a variant of the compound coupling of Fig. 3.

[0028] Across the exemplary embodiments, identical or corresponding elements have been provided with identical reference signs.

[0029] Referring to Fig. 1, a first exemplary embodiment of a compound coupling 1 for cantilevered coupling of a precast concrete slab 2 of a balcony to an in situ cast concrete storey floor 3 as concrete building element is shown. The compound coupling 1 is used to connect a precast concrete slab 2 that forms a freely protruding balcony to a building element 3 that forms a concrete storey floor 3. The connection is to be made after the floor 3 has been cast, e.g. when all storey floors 3 of the building have been put up and a facade of the building is to be completed. The concrete slabs 2 are placed without temporary support by hoisting them into place using a crane, and are cantileveredly coupled to the concrete storey floor 3 using the compound coupling 1 to act between facing head surfaces 4, 5 of the concrete slab 2 and the concrete storey floor 3 respectively.

[0030] The compound coupling 1 is embodied as a mechanical coupling, i.e. a coupling that relies on mechanical engagement of parts only to provide at least an initial load bearing connection between the concrete slab 2 and the concrete storey floor 3. In this embodiment, two compound couplings 1 placed in parallel in coupled state together provide the final and full load bearing connection between the concrete slab 2 and the storey floor 3. The compound coupling 1 is arranged to improve thermal insulation between the concrete slab 2 and the concrete storey floor 3. It includes a thermal insulation body 6 in a gap 9 between the facing head surfaces 4, 5 of the concrete slab 2 and the concrete storey floor 3 provided by the compound coupling 1, and includes stainless steel elements of low thermal conductivity in the coupling section parts, in particular the coupling section parts that are at least partially located in or that traverse the gap 9.

[0031] The compound coupling 1 includes a tension coupling section 7 forming an upper part of the compound coupling 1, and a compression coupling section 8 forming a lower part of the compound coupling 1. The tension coupling section 7 is a section of the compound coupling 1 where tension forces are transmitted between the concrete slab 2 and the storey floor 3, and is located at the level of the top half of the concrete slab 2 when installed. The compression coupling section 8 is a section of the compound coupling 1 where compression forces are transmitted between the concrete slab 2 and the storey floor 3.The compression coupling section 8 includes a pressure body 10 that is arranged in the gap 9 between the head surface 4 of the concrete slab 2 and the head surface 5 of the concrete storey floor 3. The compression coupling section 8 is located at the level of the lower half of the concrete slab 2. In Fig. 1, a horizontal dashed line H is drawn to illustrate the division between the lower half and the upper half of the concrete slab 2 and the concrete element 3. The tension coupling section 7 is in use located higher than a pressure body 10 of the compression coupling section 8. The tension coupling section 7 forms an upper part of the compound coupling 1, and the compression coupling section forms a lower part of the compound coupling 1.

[0032] In this embodiment, the pressure body 10 can, in addition to transferring compressive forces, also transfer shear forces. It has relatively large dimensions in height direction, and engages in both a form-fit closed and force-fit with the head surfaces 4,5 of respectively the concrete slab 2 and the concrete storey floor 3. In this embodiment, the pressure body 10 thus integrally serves as a stiffening diagonal.

[0033] The compound coupling 1 includes a set of cooperating building-sided tension coupling parts 11 and slab-sided tension coupling parts 12 that are anchored in facing end portions 13, 14 of the concrete slab 2 and the concrete building element 3 respectively. The tension coupling section parts 11, 12 are connected so that they cooperate, and extend from one end portion 13;14 to the other 14;13 to traverse the gap 9 between the head surface 4 of the concrete slab 2 and the head surface 5 of the concrete building element 3.

[0034] The compound coupling 1 includes at least one concrete insert piece 15 that is cast into the end portion 14 of the concrete building element 3. In this embodiment, the concrete insert piece 15 has been cast from Ultra High Performance Concrete (UHPC), and has been machined to include through holes 16. As an alternative, in a more simple embodiment it may be cast from High Performance Concrete (HPC). The compressive strength of the UHPC of the insert piece 15 is e.g. 120 MPa, which is higher than the compressive strength of the concrete building element it is to be cast into, which is e.g. around 20 to 50 MPa. The compressive strength may be measured as the characteristic (5%) cylinder strength f ck , determined at 28 days in accordance with EN 206 / EN 1992-1-1.

[0035] In this exemplary embodiment, the concrete insert piece 15 is configured to be a component of the building sided tension coupling parts 11, i.e. the building sided tension coupling section 7. The concrete insert piece 15 is arranged to form a part of the head surface 5 of the end portion 14 of the precast concrete building element 3 it has been cast into.

[0036] In this embodiment, the insert piece 15 is embodied as an anchoring block 17 that forms a section of the edge portion 18 of the concrete building element 3. It forms a corner piece of the concrete building element 3, and has been configured to form a portion of both the head surface 5 and the top surface 19 of the concrete building element 3 that it has been cast into. This allows the formwork for the concrete building element 3 to be relatively simple, and allows the critical corner portion of the concrete building element 3 to be of controlled quality. It also allows controlled positioning of the building-sided tension coupling section parts 11.

[0037] The through holes 16 of the anchoring block 19 allow passage of cast-in tension elements, in this example tension bars 12a, of the slab-sided coupling part 12 of the tension coupling section 7 therethrough. The tension bars 12a include threaded ends 20 that in the coupled condition shown protrude through the anchoring block 17, and that are secured against the anchoring block 17 with nuts 21 while optionally including washers 22. This allows transfer of the tension load exerted via the tension bars 12a to be transferred onto the anchoring block 17 as a compressive load. The anchoring block 17 transfers the load to the surrounding concrete of the concrete building element 3. To further enhance transfer of the load, the anchoring block may be provided with one or more anchoring elements, in this example anchoring rods, extending therefrom to anchor the anchoring block in the concrete of the concrete building element 3 that it is cast into. The anchoring block 17 has been provided with a removable spacer element (not shown) to form the cavity 23 in the concrete of the concrete building element 3 behind the anchoring block. This facilitates to provide space for the threaded ends 20 of the tensions bars 12a to protrude through the holes 16 in the tension block 17, and for placement and tightening of the nuts 21 and washers 22. The cavity 23 is set back from the head surface 5 of the storey floor 3, which here corresponds to the plane of the facade of the building, at a distance that corresponds to the thickness of a wall (shown smaller than to scale). This still allows access to it after a wall has been placed on the storey floor 3.

[0038] The compression coupling section 8 includes a pressure body 10 that is arranged in the gap 9 between the head surface 4 of the concrete slab 2 and the head surface 5 of the concrete storey floor 3. To facilitate transfer of shear forces and to facilitate placement of the pressure body, the pressure body 10 is held in recesses that are provided in the head surface 4 of the concrete slab and the head surface 5 of the concrete building element. The pressure body may e.g. be embodied as a steel profile section, or e.g. a UHPC block.

[0039] Referring to Fig. 2, a second exemplary embodiment is shown in which a part of the concrete insert piece 15 has further been configured to support a coupling part. In particular, a part of the concrete insert piece 15 has been configured as a concrete pressure distribution plate 24 to support the pressure body 10. The pressure distribution plate 24 forms an edge section 25 of the end portion 14 of the concrete building 3 element it has been cast into. The concrete pressure distribution plate 24 includes a recess to receive an end face of the pressure body 10 in form-fit engagement.

[0040] The concrete pressure distribution plate 24 forms part of the compression coupling section 8, in particular of the building sided compression section parts 11. The concrete pressure distribution plate 24 has in this exemplary embodiment been cast of UHPC. It absorbs the pressure of the pressure body 10 and distributes the pressure over the concrete of the concrete building element 3, which can thus have a significantly lower pressure resistance than the concrete of the pressure distribution plate 24. As is the case with the anchoring block 17, the concrete pressure distribution 24 may be cast as a prefabricated insert. The concrete pressure distribution plate 24 in this example has been cast from UHPC having the same compressive strength as the anchoring block, but may also be cast with a different, e.g. lower compressive strength than the anchoring block. The lower part of the concrete insert piece 15 is arranged as a pressure distribution plate 24 that forms an edge section 25 of the end portion 14 of the concrete building element 3 that it has been cast into, and an outer surface of the concrete insert piece 15 is configured to form the head surface 5 of the concrete building element onto which the pressure body 10 is supported.

[0041] The concrete pressure distribution plate 24 and concrete anchoring block 17 of Figure 2 have been cast as two separate pieces that have been connected with glue to facilitate installation in the formwork. The two pieces together form two modules of the concrete insert piece 15 that in this example extends over the full height of the concrete building element 3. By building the concrete insert piece up of modules, its construction can be facilitated, and its configuration can adapted to different uses, e.g. different slab heights, relatively easily. In a variant, an intermediate piece may be provided that serves as a spacer element between the anchoring block 17 and the pressure distribution plate 24 to adapt to different slab heights still more easily. To save costs, this spacer element may e.g. include concrete of lower compressive strength than the pressure distribution plate 24 and concrete anchoring block 17.

[0042] Referring to Figs. 3 and 4, further exemplary embodiments of the compound coupling 1 are shown. In Fig. 3 the concrete insert piece 15 has been cast as 2-part insert piece in a two-step casting process, and in Fig. 4 the insert piece has been cast as a 1-piece insert piece in one singular block with integrally the same functions as in Fig. 3, including an anchor block as upper (tension) part and a compression distribution plate as lower (compression) part.

[0043] The concrete insert piece 15 includes an UHPC anchoring block 17 that has been cast with through holes 16 using removable cores. The through holes 16 are arranged for passing a tension bar of the slab-sided coupling section part 12 of tension coupling section 7 therethrough. The anchoring block 17 further includes a plurality of cast-in anchoring rods 31 extending therefrom that in use anchor the anchoring block 17 in the concrete of the concrete building element 3 that it has been cast into. In addition, the anchoring block 17 further includes a cast in connecting bracket 32. The concrete insert piece further includes an UHPC pressure distribution plate 24 that is cast to the anchoring block in a second step of the process of precasting the concrete insert piece15, such that the connecting bracket 32 ensures a strong force transferring connection between the anchoring block 17 and the pressure distribution plate 24. The bracket 32 may be used to ensure that the shear forces are transferred / anchored back into the more central slab area, thus preventing a spalling / break-out near the underside of the slab, e.g. in cases when a window is provided in the wall of the storey below. In variants where there is sufficient support, a sliding layer may be provided between the anchoring block for the tension forces and the pressure distribution plate for the compression and shear forces. In addition, the connecting bracket 32 can serve to anchor the distribution plate 24.

[0044] As is the case with second exemplary embodiment, the concrete insert piece 15 forms an edge section 25 of the end portion 14 of the concrete building element 3 that it is to be cast into, and the outer surface of the concrete insert piece 15 is configured to form the head surface 5 of the concrete building element onto which the pressure body 10 is supported. A protruding end 33 of the connecting bracket 32 is to be embedded in the concrete of the of the concrete building element 2.

[0045] To enable transfer of shear force, the compound coupling 1 is in this embodiment provided with a stiffening diagonal 27. The stiffening diagonal 27 has a central bracket part 28 that extends obliquely between an attachment part 29 that is arranged to be attached to the head surface 5 of the concrete building element 3 and a support part 30 that is arranged to support the concrete slab 2 and that in use is located lower than the attachment part 29. The attachment part 29 is folded over a support block 38 and is provided with a bolt hole 39 for allowing a connecting bolt 37 to pass therethrough. The attachment part 29 of the stiffening diagonal 27 extends in a flat plane, and in use extends vertically to match the orientation of the head surface 5 of the storey floor 3. The central bracket part 28 of the stiffening diagonal 27 also extends in a flat plane, and in use extends diagonally. In this embodiment, the central bracket part 28 includes two central members arranged in parallel, each with a common attachment part 29 and a common support part 30. In this embodiment, the support part 30 extends in two flat planes, a substantially horizontal support plane 30a and a substantially vertical support plane 30b for support of the concrete slab 2. The stiffening diagonal 27 in this example is plate-shaped, and has been laser cut from stainless sheet steel. After cutting, the central bracket part 28, the attachment part 29 and support part 30 of the stiffening diagonal 27 have been set using an angle bending machine. The stiffening diagonal 27 is in this embodiment manufactured in one piece, and is free from welds. A more detailed description of a suitable stiffening diagonal 27 is provided in Dutch patent application No. 2036530 in the name of applicant.

[0046] The stiffening diagonal 27 is arranged to be detachably connected to the concrete building element 3 via the concrete insert piece 15. In particular, an anchoring element, in this example an anchoring bar 36, is cast into the pressure distribution plate 17 of the concrete insert piece 15, which may be anchored to reinforcements of the concrete of the building element 3 that are present in the formwork before casting of the building element 3. The anchoring bar 36 is provided with a thread insert extending to the face of the insert piece 15 that is to form the head surface 5 of the concrete floor, so as to receive a connecting bolt 37 with which the stiffening diagonal 27 can be bolted to the concrete insert piece 15 when the facade of the building is prepared for coupling the concrete slab 2 of the balcony thereto. This way, the stiffening diagonal 27 can not only advantageously be provided after casting of the storey floor 3, but can e.g. also be uncoupled for re-use or recycling. In a variant of this construction, the anchoring element, e.g. the anchoring bar 36, may be provided with an external thread to receive a nut which is used to bolt the stiffening diagonal 27 to the concrete insert piece 15. To prevent a need for penetration of the formwork with the anchoring bar when casting, the concrete insert piece can be provided with a recess to create space for the nut. The attachment part of the stiffening diagonal may together with the support block 38 be positioned within that recess. As mentioned above, in this third exemplary embodiment a pressure body 10 is enclosed in the gap 9 between the support part 30 of the stiffening diagonal 27 and the head surface 5 of the concrete building element 3, which is formed by the concrete insert piece 15. The pressure body 10 has a head surface 34 that is arranged for cooperation with the support part 30 of the stiffening diagonal 27. It further has a tail surface 35 that is arranged for cooperation with the portion of the head surface 5 of the concrete building element 3 that is formed by the pressure distribution plate 24 of the concrete insert 15.

[0047] The pressure body 10 is in this third exemplary embodiment made from UHPC, by casting the UHPC having a compressive strength equal to that of the UHPC pressure distribution plate. The UHPC may e.g. be cast into a plastic sleeve that acts as a mold. The pressure body 10 may be used to transfer a large part of the gravity force acting on the concrete slab 2 to the concrete building element 3. This capacity may be enhanced by orienting the pressure body 10 and the support planes 30a, 30b of the support part at a slant. The pressure body 10 may then e.g. extend downward from the support part 30 to the concrete pressure distribution plate 24, i.e. in a direction from the concrete slab 2 towards the storey floor 3. An example of such downward slanting configuration of a pressure body is provided in the exemplary embodiment of Figures 1-4 of applicant's Dutch patent application NL2036530.

[0048] In the coupling process, as shall be discussed further below, the compression coupling section 8 of the compound coupling 1 can be engaged by simply supporting a part of the slab-sided edge section 40 of the concrete slab 2 on the support part 30.

[0049] The compression coupling section 8 is free of slab-sided compression coupling elements, and the concrete slab 2 is free of anchoring means for such slab-sided compression coupling elements. This facilitates the formwork of the precast concrete slab 2 as it can be straight and closed at the lower end of the head surface 4 to be formed, and only requires boreholes to accommodate protruding slab-sided tension bars 20. Also, manufacturing of the precast concrete slab 2 can be simplified, as no slab-sided compression coupling section needs to be provided that would otherwise have to be anchored to the reinforcement bars of the concrete slab 2.

[0050] The coupling process is prepared as follows. Before casting the concrete storey floor 3, the precast UHPC insert piece 15 is positioned in the formwork and is anchored with its anchoring bar 36 to reinforcements for the building element 3 that are present in the formwork. Then, the concrete building element 3 is cast in situ, such that the concrete insert piece 15 forms an edge section of the concrete building element 3, and forms the head surface 5 of the concrete storey floor that is flush with the building's facade.

[0051] The concrete storey floor can be cast in the formwork without any building-sided coupling sections protruding through the formwork. After hardening of the concrete, the spacer elements on the anchoring block 17 are removed to clear the cavity 23 for receiving the treaded free ends of the tension bars 14. Next, the stiffening diagonal 27 including a support block 38 as well as a pressure body 10 is connected to the thread inserts in the face of the concrete insert piece 15 using connecting bolts 37 to prepare the facade of the building for coupling the concrete slab 2 of the balcony thereto. In a variant of this construction, the anchoring bar 36 may be provided with an external thread to receive a nut which is used to connect the stiffening diagonal 27 to the concrete insert piece 15.

[0052] The coupling process for the exemplary embodiment is e.g. carried out as follows. The coupling process starts by hoisting the concrete slab 2 into position using a crane and moving it towards the facade of the building so that the threaded free ends 20 of tension bars 12a of the slab-sided tension coupling section parts 12 of the tension coupling section 7 protrude through the through holes 16 of the insert piece into the cavity 23.

[0053] After the concrete slab 2 has been moved towards the storey floor 3 as discussed above, the precast concrete slab 2 is lowered slightly until a part of the slab-sided edge section 40 of the concrete slab 2, in particular a lower corner of the concrete slab 2, is supported on the support part 30. When supported on the support part 30, a set of building-sided inner chains of the crane may be slackened, and a set of outer chains may be raised or lowered while the precast concrete slab 2 is levelled. After levelling, the tension coupling parts 11,12 can be fixedly coupled by screwing nuts onto the threaded free ends of the slab sided tension bars 12a of the slab-sided tension coupling section.

[0054] Many variations will be apparent to the skilled person in the art. For example, the anchoring block may be provided on the concrete slab instead of on the concrete building element. Also, a pressure distribution plate may be provided without anchoring block, e.g. in combination with a conventional steel tension plate. Also, the concrete building element may be precast instead of cast in situ as in the example, and may e.g. be a wall element instead of a storey floor. The precast slab may further e.g. be part of a cantilevered parapet, canopy or walkway instead of a balcony as in the example. Such variations are understood to be comprised within the scope of the invention as defined in the appended claims.List of reference signs

[0055] 1. Compound coupling 2. Precast concrete slab 3. Concrete storey floor (Concrete building element) 4. Head surface concrete slab 5. Head surface concrete storey floor 6. Thermal insulation body 7. Tension coupling section 8. Compression coupling section 9. Gap 10. Pressure body 11.Building-sided tension coupling section parts 12. Slab-sided tension coupling section parts 12a. Slab-sided tension bar of the slab-sided tension coupling section 13.End portion slab 14. End portion building element 15.Insert piece 16.Hole 17. Anchoring block 18.Edge portion building element 19.Top surface 20. Threaded end 21.Nut 22. Washer 23. Cavity 24. Concrete pressure distribution plate 25. Edge section 26. - 27. Stiffening diagonal 28. Central bracket part 29.Attachment part 30. Support part 30a. Substantially horizontal support plane 30b. Substantially vertical support plane 31. Tension anchoring element 32. Connecting bracket 33. Protruding end 34. Head surface of pressure body 35. Tail surface of pressure body 36. Shear force anchoring element 37. Connecting bolt 38. Support block 39.Bolt hole 40. Slab-sided edge section H horizontal line between lower half and the upper half of concrete slab

Claims

1. A compound coupling for cantilevered coupling of a precast concrete slab, in particular a balcony, a parapet, a canopy or a walkway, to a concrete building element, in particular a storey floor or wall element, the compound coupling including a set of cooperating building-sided and slab-sided coupling parts that in use are anchored in and / or supported on facing end portions of the concrete slab and the concrete building element respectively, wherein the compound coupling includes at least one concrete insert piece that is to be cast into an end portion of the concrete slab or concrete building element.

2. The compound coupling of claim 1, wherein the concrete of the insert piece comprises High Performance Concrete (HPC) or Ultra High Pressure Concrete (UHPC).

3. The compound coupling of claim 1 or 2, wherein the concrete compression strength of the concrete of the insert piece is higher than the pressure resistance of the precast concrete slab or the concrete building element it is to be cast into, preferably by at least 30 MPa, more preferably by at least 50 MPa.

4. The compound coupling of any of claims 1-3, wherein the concrete insert piece is configured to be a component of a coupling part and / or is configured to support a coupling part.

5. The compound coupling of any of claims 1-3, wherein the concrete insert piece is a component of a coupling part.

6. The compound coupling of any of claims 1-5, wherein the concrete insert piece is configured to form at least a part of a head surface of an end portion of the precast concrete slab or the concrete building element it is to be cast into.

7. The compound coupling of any of claims 1-6, wherein the concrete insert piece is configured to form an edge section of an end portion of the precast concrete slab or the concrete building element it is to be cast into.

8. The compound coupling of any of claims 1-7, wherein the concrete insert piece comprises two or more concrete modules.

9. The compound coupling of any of claims 1-8, wherein the compound coupling includes a tension coupling section that in use forms an upper part of the compound coupling, the tension coupling section including a set of cooperating building-sided and slab-sided tension section parts that in use are anchored to facing end portions of the concrete slab and the concrete building element respectively, and that, when cooperating, extend from one end portion to the other, in particular to traverse a gap between a head surface of the concrete slab and the head surface of the concrete building element.

10. The compound coupling of any of claims 1-9, wherein the insert piece includes a block that forms a section of the edge portion, in particular a corner piece, of the precast concrete slab or the concrete building element, and is configured to form a portion of the head surface and / or a top surface of the precast concrete slab or the concrete building element it is to be cast into.

11. The compound coupling of any of claims 1-10, wherein the concrete insert piece is part of one of a slab- or building sided coupling part of a tension coupling section, and comprises an anchoring block with one or more predefined holes for passing a tension element of the other of a slab- or building sided coupling part of a tension coupling section therethrough.

12. The compound coupling of any of claims 1-11, wherein the concrete insert piece is part of one of a slab- or building sided coupling part of a tension coupling section, and comprises an anchoring block with one or more anchoring elements extending therefrom to anchor the anchoring block in the concrete of the precast concrete slab or the concrete building element that it is to be cast into.

13. The compound coupling of any of claims 1-12, wherein the concrete insert piece is provided with a removable spacer element for forming a cavity in the concrete of the precast concrete slab or the concrete building element that it is to be cast into.

14. The compound coupling of any of claims 1-13, wherein the compression coupling includes a compression coupling section that in use forms a lower part of the compound coupling, and wherein the compression coupling includes a pressure body that is configured to be arranged in the gap between the head surface of the concrete slab and the head surface of the concrete storey floor.

15. The compound coupling of claim 14, wherein the pressure body is a concrete pressure body, preferably a HPC pressure body, more preferably a UHPC pressure body.

16. The compound coupling of claims 14 or 15, wherein the concrete insert piece is configured to support the pressure body.

17. The compound coupling of any of claims 14-16, wherein the insert piece is arranged as a pressure distribution plate, preferably a pressure distribution plate onto which a pressure body is directly or indirectly supported.

18. The compound coupling of claim 17, wherein the concrete insert piece that is arranged as a pressure distribution plate forms an edge section of an end portion of the precast concrete slab or the concrete building element it is to be cast into, and wherein an outer surface of the insert piece is configured to in use form part of the head surface of the concrete slab or the concrete building element onto which the pressure body is supported.

19. The compound coupling of any of claims 1-18, wherein the compound coupling further comprises a stiffening diagonal having a central bracket part that extends obliquely between an attachment part that is arranged to be attached to the head surface of the concrete building element of the building and a support part that is arranged to support the concrete slab and that in use is located lower than the attachment part.

20. The compound coupling of claim 19 and any of 14-18, wherein the pressure body is arranged with a head surface that is arranged for cooperation with the support part and a tail surface that is arranged for cooperation with the head surface of the concrete building element, in particular a portion of the surface that forms part of the concrete pressure distribution plate, which pressure body in use is enclosed in a gap between the support part of the stiffening diagonal and the head surface of the concrete building element.

21. The compound coupling according to claims 19 or 20, wherein the stiffening diagonal [MF1] is arranged to be detachably connected to the concrete building element, preferably to the concrete insert piece, more preferably to the concrete insert piece as specified in claim 18 or 19.

22. A precast concrete slab, in particular a balcony, a parapet, a canopy or a walkway, or concrete building element, in particular a storey floor or wall element, including a compound coupling according to any of the preceding claims.

23. A method of casting a concrete slab, in particular a balcony, a parapet, a canopy or a walkway, or concrete building element, in particular a storey floor or wall element, more in particular a concrete slab or concrete building element as specified in claim 22, in which method a concrete insert piece of a compound coupling according to any of claims 1 - 21 is included in the formwork to be embedded in the concrete of the slab or building element to be cast.

24. A building comprising a façade and at least one concrete building element, in particular a storey floor or wall element, to which at least one precast concrete slab, in particular a balcony, a parapet, a canopy or a walkway, has been cantiliveredly coupled via a compound coupling according to any of claims 1-21.

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