Flat component, shear force reinforcing element, and reinforced concrete/prestressed concrete component with a shear force reinforcement of such shear force reinforcing elements

Abstract

The invention relates to L-shaped sheet metal parts 21 with an angled longitudinal recess 23 as well as a reinforced concrete/prestressed concrete component with at least one upper and at least one lower longitudinal reinforcement layer and a shear force reinforcement guided in its dimension over the uppermost and the lowermost longitudinal reinforcement, which is formed from the L-shaped sheet metal parts 21 according to the invention with stirrups 30 fastened in the longitudinal recess 23. The reinforced concrete/prestressed concrete component according to the invention is suitable for increasing the punching shear resistance in the region of slab columns of flat slabs.

Claims

1. A flat component of metal configured to provide a shear force reinforcing element (Q) and suitable for mounting a stirrup (30) thereto, comprising a lower section, configured for connection with a lower longitudinal reinforcement of a reinforced or prestressed concrete component, wherein the flat component has an angled longitudinal recess (23) ending in a fastening region (BF) and having a feed channel (S) connected thereto and opening to a vertical side edge or an upper horizontal edge of the flat component, wherein the feed channel has a feed angle ? of between 10? to 120? to the horizontal and the fastening region (BF) is either horizontal or slightly inclined upwards as it extends away from the feed channel and toward a vertical centerline (M) of the flat component, and wherein the feed channel (S) is straight or arcuate and terminates in an opening (29) capable of feeding a stirrup arch (34), and further including a first recess (25a) on a lower edge of the feed channel (S) adjacent the opening (29) and a second (26a) recess on an outer edge of the flat component adjacent the opening (29), the two recesses opening generally in opposite directions so as to enable mounting a clip plate part (24a) for securing the stirrup (30) in the fastening region (BF).

2. The flat component according to claim 1, wherein the feed angle ? comprises a range of 10? to 110?.

3. The flat component according to claim 1, wherein the feed angle ? comprises a range of 10? to 80?.

4. The flat component according to claim 1, wherein the feed angle ? comprises a range of 80? to 110?.

5. The flat component according to claim 1, wherein the feed angle ? comprises a range of 40? to 50?.

6. The flat component according to claim 1, wherein the feed channel (S) and the fastening region (BF) both have a height of about 8 mm, so that a stirrup (30) having a nominal diameter of 6 mm is freely movable in the angled longitudinal recess (23).

7. The flat component according to claim 1, wherein the fastening region (BF) has an upper recess with a height of 1 mm or a slightly inclination which rises by about 1 mm as it extends in the direction of the center line (M) which supports the fixing of the arches (34).

8. The flat component according to claim 1, wherein the angled longitudinal recess (23) has a depth T=(30?1) mm and the feed channel (S) has a feed angle ?=45? and a length of (16?1) mm.

9. The flat component according to claim 1, wherein the lower section has a right-angled bend (40).

10. The flat component according to claim 1, wherein the flat component is made of structural steel.

11. A shear force reinforcing element (Q) for a reinforced or prestressed concrete component, comprising: a flat component of metal configured to provide a shear force reinforcing element (Q) and suitable for mounting a stirrup (30) thereto, comprising a lower section, configured for connection with a lower longitudinal reinforcement of a reinforced or prestressed concrete component, wherein the flat component has an angled longitudinal recess (23) ending in a fastening region (BF) and having a feed channel (S) connected thereto and opening to a vertical side edge or an upper horizontal edge of the flat component, wherein the feed channel has a feed angle ? of between 10? to 120? to the horizontal and the fastening region (BF) is either horizontal or slightly inclined upwards as it extends away from the feed channel and toward a vertical centerline (M) of the flat component; and at least one stirrup (30) fastened to the flat component.

12. A shear force reinforcement element (Q) according to claim 11, wherein a stirrup length H.sub.B of the at least one stirrup (30), with respect to a minimum stirrup length h.sub.B equal to the distance from an upper edge of the fastening region BF recess to the upper edge of an uppermost longitudinal reinforcement layer to which the shear force reinforcing element (Q) mounts plus twice a nominal diameter of the stirrup (30), satisfies the condition h.sub.B<H.sub.B?1.06.Math.h.sub.B.

13. A shear force reinforcement element (Q) according to claim 12, wherein the stirrup length H.sub.B is selected from the group consisting of: H.sub.B=1.06.Math.h.sub.B, H.sub.B=1.05.Math.h.sub.B, H.sub.B=1.04.Math.h.sub.B, H.sub.B=1.03.Math.h.sub.B, H.sub.B=1.02.Math.h.sub.B and H.sub.B=1.01.Math.h.sub.B.

14. A shear force reinforcing element (Q) according to claim 12, wherein the stirrups are made of reinforcing steel.

15. A shear force reinforcing element (Q) according to claim 12, wherein a stirrup length H.sub.B of the at least one stirrup (30) is equal to the minimum stirrup length h.sub.B.

16. The flat component according to claim 11, wherein the lower section has a right-angled bend (40).

17. A reinforced or prestressed concrete component with an upper and a lower longitudinal reinforcement, comprising: at least one shear force reinforcing element (Q) with a flat component of metal configured to provide a shear force reinforcing element (Q) and suitable for mounting a stirrup (30) thereto, comprising a lower section, configured for connection with a lower longitudinal reinforcement of a reinforced or prestressed concrete component, wherein the flat component has an angled longitudinal recess (23) ending in a fastening region (BF) and having a feed channel (S) connected thereto and opening to a vertical side edge or an upper horizontal edge of the flat component, wherein the feed channel has a feed angle ? of between 10? to 120? to the horizontal and the fastening region (BF) is either horizontal or slightly inclined upwards as it extends away from the feed channel and toward a vertical centerline (M) of the flat component; and and at least one stirrup (30) connected to the flat component, whereby the at least one stirrup (30) of the at least one shear force reinforcing element (Q) has a connection to the upper longitudinal reinforcement of the reinforced or prestressed concrete component and the flat component has a connection to the lower longitudinal reinforcement of the reinforced or prestressed concrete component.

18. A reinforced or prestressed concrete component according to claim 17, wherein the upper longitudinal reinforcement is a reinforcing mat.

19. The flat component according to claim 17, wherein the lower section has a right-angled bend (40).

Description

DETAILED DESCRIPTION OF THE INVENTION

Part 1 of the Solution: Flat Component 21 According to the Invention, Shear Force Reinforcement Element Q and Reinforced Concrete/Prestressed Concrete Component Equipped Therewith

(1) A large number of tests with flat components having different shapes of longitudinal recesses showed that the object of the invention is optimally solved by a flat, preferably rectangular, component 21 and at least one stirrup 30 mountable to the flat component 21. The flat component 21 is provided in its lower section with at least one holding means for fastening to the lower longitudinal reinforcement of a reinforced concrete/prestressed concrete component. These holding means comprise sufficiently large recesses 50 for fastening the flat component 21 to bars of the lowest longitudinal reinforcing layer Buu, as well as an optional bend 40 immediately below the recess(es) 50. The recesses 50 can lie completely inside the flat component 21, so that a bar of the lowest reinforcing layer Buu can be passed through each of the recesses 50. In order to prevent the flat component 21 from rotating about such a bar, the flat component 21 preferably has two recesses 50 for the positioning of such bars, which secure the flat component 21. Instead of completely inside the flat component 21, the recesses 50 can also be designed to be open or semi-open to the side edges of the flat component 21. In this case, a bar of the lowest reinforcing layer Buu can be introduced from the sides into a recess 50 of the flat component 21. The optional bend 40 is designed at a right angle and offers the possibility of an additional stabilization of the flat component 21 by resting directly against the undersides of bars of the lowest reinforcement layer Buu positioned in the recesses 50. Advantageously, the bend 40 is provided with additional recesses (as can be seen in FIG. 2c, bottom), which permit the passage of fixing wires with which the bend 40 is drawn up to the bars of the lowest reinforcement layer Buu, so that the flat component 21 is fixed tilt-proof and non-displaceable (so-called wire-tying). Due to this additional stabilizing function, the design of the flat component 21 with a bend 40 is absolutely preferable.

(2) The flat component 21 has a fastening region BF which is designed as a recess, which is located in the vicinity of the center line M of the flat component 21 and is suitable for positioning the arches of one or two stirrups 30. The fastening region BF is designed such that it has a defined distance from the upper longitudinal reinforcement after installation of the flat component 21 in a reinforced concrete/prestressed concrete component. The fastening region BF is therefore preferably designed as a horizontal slot. To enable a more stable fixing of the stirrups 30, it can also be slightly inclined or have an additional recess on its top side (in the direction of the upper edge of the flat component 21) for receiving the stirrup arches 34.

(3) According to the invention, the flat component 21 furthermore has a feed region which is designed as a recess A and is connected to the fastening region BF, which allows the feeding of an arch 34 to the fastening region BF in a large angular range, whereby the feed angle ?, measured from the horizontal, is variable between at least 10? and 120?. A recess A, which allows this large angular range, extends over an area which is delimited by the upper section of a side edge and a part of the upper edge of the flat component 21 and is marked by a dashed line in FIG. 2a. FIG. 2a shows that the feeding of a stirrup arch 34 can be carried out extremely variably, e.g. at angles of 10?, 30?, 45?, 60?, 90? and 120? as indicated in this sequence by arrows a to f.

(4) In a preferred embodiment of the invention, the recess A is narrowed in a manner that allows the feeding of an arch 34 only in a suitable angular range to be selected from the range 10????120?. Suitable angle ranges are 10????110?, preferably 80????110? (whereby the operator can see the feeding area from above and can position the stirrup more quickly and securely) and 10????80? (whereby a good guidability of the stirrup arch 34 is ensured at the lower edge of the funnel-shaped recess A), and, more preferably, 40????50? (whereby an optimum compromise of the operator's effort and the guidability of the stirrup is achieved).

(5) In a further preferred embodiment of the invention, the recess A is narrowed in a manner that allows the feeding of an arch 34 only at a selected feed angle, which is also to be selected from the range 10????120?. Preferred feed angles are ?=30?, ?=45?, ?=60?, a particularly preferred angle is ?=45?. In these cases, the feed region, formed by the recess A, narrows to a feed channel S in the form of an obliquely upwardly directed slot with an opening 29 to the exterior which is suitable for feeding an arch 34. A feed channel S like this together with the fastening region BF forms an angled longitudinal recess 23.

(6) Due to the oblique course of the feed channel S, the distance between the opening 29 and the upper longitudinal reinforcement is less than the distance between the fastening region BF and the upper longitudinal reinforcement (after installation of the flat component 21 in a reinforced concrete/prestressed concrete component). This feature is a crucial prerequisite for the use of short stirrups 30. The feed channel S is preferably designed in a straight line, but it can also be arcuate, with the arc radius corresponding to the distance between the fastening region BF and the upper longitudinal reinforcement (as indicated in dashed line in FIG. 2b).

(7) The vertical positioning of the fastening region BF and the height of the flat component 21 result from the following considerations: The distance of the fastening region BF from the lower, preferably bent side of the flat component 21 must be so great, that the fastening region BF remains freely accessible when the flat component 21 is installed in a prestressed concrete component which is constructed as a semi-precast part, which is already poured with concrete. Since the casting height in practice amounts 4 cm to 6 cm over the lower longitudinal reinforcement, the fastening region BF should be at least 7 cm from the lower side of the flat component 21. In order to ensure that the flat component 21 also has the necessary stability in the region of the angled longitudinal recess, at least one third of its surface should lie above the fastening region BF. On the other hand, the flat component 21, installed in a reinforced concrete/prestressed concrete component, must have a sufficient distance from its upper longitudinal reinforcement, even for reinforced concrete/prestressed concrete elements of small thickness (near or equal to a minimum thickness of 18 cm). A flat component 21 having a height between 11 cm and 12 cm and a fastening region BF, which is 7 cm to 8 cm from the lower side of the flat component 21, solves the object of the invention. The flat component 21 and the stirrups 30 must consist of a material of high tensile strength. Suitable materials which combine a high tensile strength with an easy workability are structural steel and reinforcing steel, whereby structural steel is preferred for the flat components 21, whereas reinforcing steel is preferred for the stirrups 30. If it is made of structural steel, the flat component 21 should have a thickness of at least 1 mm, preferred thicknesses are 3 mm and 5 mm. For the stirrups 30, ribbed reinforcing bar steel with a nominal diameter of 6 mm is preferably used. Other tensile-strength materials can also be used, whereby the dimensions may be adapted by a person skilled in the art.

(8) FIG. 2b shows the schematic representation of a preferred embodiment of a flat component 21 according to the invention, which is equipped with an angled longitudinal recess 23. As it is preferably made of structural steel and has an optional, but absolutely preferable, bend 40, which gives it an L-shaped cross-section, it is designated as an L-shaped sheet metal part 21 in the following and in all the exemplary embodiments. In the fastening region BF, one or two stirrups 30 (not shown in FIG. 2b) can be installed.

(9) On the lower edge of the feed channel S of the angled longitudinal recess 23 and on the side edge of the L-shaped sheet metal part 21, there are two recesses 25a and 26a which form a notched projection 27a, at which a clip plate part 24a can be snapped in by pushing it in the direction of the arrow shown in FIG. 2b for fixing and securing the stirrups 30. In order to ensure a secure snapping-in of the clip plate part 24a, the recess 25a is preferably of a rectangular design. The shape of the recess 26a is largely freely selectable. It is preferably designed as a triangle, which is large enough that the clip plate part 24a can be installed. Thus, the load-bearing capacity of the L-shaped sheet metal part 21 is not impaired by the recess 26a.

(10) The feed angle ? at which a stirrup arch 34 can be fed in, is determined in this configuration by the inclination angle ? of the feed channel S against the fastening region BF (?=?). The inclination angle ? is selectable from the same range as ?. The range 30????60? in which also short stirrups 30 can be reliably fed in is preferred, whereby the angles ?=30?, ?=45? and ?=60? are particularly preferred, i.e. the angles which are also preferred for ?. The lengths L.sub.S of the feed channel S and L.sub.BF of the attachment region BF are variable relative to one another, whereby the equation L.sub.S.Math.cos ?+L.sub.BF=T is fulfilled. T is the depth of the longitudinal recess 23 (extending from the side edge of the L-shaped sheet metal part). Preferably, the depth T of the angled longitudinal recess 23 extends by one stirrup diameter beyond the center line M of the L-shaped sheet metal part 21 so that the fastening region BF lies precisely in the region of the center line M and the L-shaped sheet metal part 21 is thus evenly loaded. However, in order to increase the load-bearing capacity of the L-shaped sheet metal part 21, a smaller depth T can be selected as shown in FIG. 2b.

(11) The length L.sub.BF of the fastening region BF is selected in such a manner and the positions of the recesses 25a, 26a for fastening the clip plate 24a are arranged in such a way that either one or two stirrup arches 34 can be inserted into the fastening region BF and secured by snapping-in a clip plate part 24a.

(12) An essential prerequisite for the installation of the stirrups 30 is, that the opening 29 of the angled longitudinal recess 23 is higher than the fastening region BF, which is ensured by the feed channel S extending obliquely upwards from the fastening region BF to the opening 29. The height difference HD between the opening 29 and the fastening region BF is given here by the projection L.sub.S.Math.sin ? of the feed channel S onto the side edge of the L-shaped sheet metal part 21. A height difference HD of 1 cm to 2 cm is sufficient in order to be able to install even short stirrups safely. In order to ensure a free movability of an arch 30 in the longitudinal recess 23, the height of the longitudinal recess 23 must be a little greater than the nominal diameter of the stirrup 30, i.e., the nominal diameter of the bar material used for producing the stirrups 30 (preferably reinforcing bar steel). The stirrup surface is preferably ribbed, which results in the outer diameter of the stirrups 30 being larger than their nominal diameter. The free movability of the arch 30 in the longitudinal recess 23 is ensured in any case if the height of the longitudinal recess 23 is one third larger than the nominal diameter of the stirrup 30. In the finished reinforced concrete/prestressed concrete element the ribbed stirrup surface forms a stable connection with the surrounding concrete and therefore increases the load-bearing capacity of the reinforced concrete/prestressed concrete component. The angled longitudinal recess 23 can be modified in various ways: The feed channel S can also be arcuate. It is important that, even in the case of an arcuate design of the feed channel, the above-mentioned height difference HD is ensured. The fastening region BF can be slightly inclined upwards in the direction of the center line M in order to assist in the fixing of the stirrups 30. A horizontally extending fastening region is preferred since it has a defined distance to the upper longitudinal reinforcement after installation of the L-shaped sheet metal part 21 in a reinforced concrete/prestressed concrete component. It is possible to provide the upper side of the fastening region BF with a recess which supports the fixing of the arches 34. The recess should have a small height of 1 mm so that the distance from the upper longitudinal reinforcement is only slightly increased. If a slightly inclined fastening region BF is selected, it should also rise along its length only by a small amount of about 1 mm in the direction of the center line M.

(13) In order to realize the object of the invention, a small inclination angle ? of the stirrup 30 in its end position (?<20?, preferably ?<10?, ideally ?=0), the following considerations are useful for selecting the stirrup lengths H.sub.B:

(14) As shown in FIG. 3, the minimum stirrup length h.sub.B is given by the distance from the upper edge of the fastening region BF of the angled longitudinal recess 23 to the upper edge of the uppermost longitudinal reinforcement layer Boo plus twice the nominal diameter of the stirrup 30. The inclination angle ? of the stirrup in its end position is determined by the ratio of the stirrup length H.sub.B to the minimum stirrup length h.sub.B according to cos ?=h.sub.B/H.sub.B. In the case of an inclined stirrup, the stirrup shoulders show a lateral offset V relative to the stirrup arch (see FIG. 3). Examples of quantitative data are shown in the following table:

(15) TABLE-US-00001 H.sub.B cos ? ? V (at h.sub.B = 12 cm) V (at h.sub.B = 30 cm) 1.41 .Math. h.sub.B 0.71 45? 12 cm 30 cm 1.15 .Math. h.sub.B 0.87 30? 6.9 cm 17.3 cm 1.07 .Math. h.sub.B 0.93 20.8? 4.6 cm 11.4 cm 1.06 .Math. h.sub.B 0.94 19.4? 4.2 cm 10.6 cm 1.05 .Math. h.sub.B 0.95 17.8? 3.9 cm 9.6 cm 1.04 .Math. h.sub.B 0.96 15.9? 3.4 cm 8.6 cm 1.03 .Math. h.sub.B 0.97 13.9? 3.0 cm 7.4 cm 1.02 .Math. h.sub.B 0.98 11.4? 2.4 cm 6.0 cm 1.01 .Math. h.sub.B 0.99 8.1? 1.7 cm 4.3 cm 1.00 .Math. h.sub.B 1 0? 0 cm 0 cm

(16) According to the above definition, characterizing stirrups 30 with an inclination angle ?<20? in the end position as short stirrups, in the above table the stirrups 30 with stirrup length 1.00.Math.h.sub.B?H.sub.B?1.06.Math.h.sub.B are classified as short stirrups, and the stirrups with stirrup lengths H.sub.B=1.07.Math.h.sub.B, 1.15.Math.h.sub.B, 1.41.Math.h.sub.B are classified as long stirrups.

(17) In order to be also able to install the stirrups 30 reliably when using reinforcing mats as the upper longitudinal reinforcement of a reinforced concrete/prestressed concrete component, the lateral offset V must be less than half the bar spacing in the reinforcing mat. A standard bar spacing is 15 cm. The table shows that stirrups with a length of H.sub.B=1.06.Math.h.sub.B can be safely installed in the case of a minimum stirrup length h.sub.B=12 cm (suitable for a concrete/prestressed concrete component of approximately 24 cm thickness). In the case of a minimum stirrup length h.sub.B=30 cm (suitable for a reinforced concrete/prestressed concrete component of approximately 42 cm thickness), the lateral offset V for stirrups of the lengths H.sub.B=1.06.Math.h.sub.B would already be too great. Stirrups of a stirrup length (H.sub.B?1.03.Math.h.sub.B) are required. Theoretically, it is possible to choose stirrups 30 of the minimum stirrup length h.sub.B, which are vertically directed in their end position (?=0). However, in practice manufacturing tolerances must always be considered, which may lead to deviations of the stirrup lengths. It is therefore not practical to use stirrups 30 with the minimum stirrup length h.sub.B, as a fraction of these stirrups could be too short and therefore could be not installable. Stirrups 30 of the stirrup length H.sub.B=1.02.Math.h.sub.B represent a suitable compromise. They have a small inclination angle in the end position (?=11.4?, if the stirrup lengths are exactly kept) and are not at risk of being unable to be installed due to manufacturing tolerances. Within the scope of this invention, however, stirrups 30 with shorter stirrup lengths (1.01.Math.h.sub.B) including the minimum stirrup length h.sub.B are also claimed, since such stirrups will become practically relevant in the future due to decreasing manufacturing tolerances. The saving of bar material is to be mentioned as an advantageous secondary effect of the use of short stirrups 30.

(18) An advantage of the shear force reinforcing element Q is that the adaptation to reinforced concrete/prestressed concrete components of different thicknesses is realized by the variation of the stirrup length H.sub.B. Thus identical L-shaped sheet metal parts 21 can be used for reinforced concrete/prestressed concrete components of different thicknesses.

Example 1 (Concerning the L-Shaped Sheet Metal Part 21)

(19) FIG. 2c shows in the front view (top left), side view (top right) and top view (bottom) a specific embodiment of the L-shaped sheet metal part 21 according to the invention, as it is provided for practical use. The reference signs, directly transferable from FIG. 2b, have been omitted in order to be able to clearly represent all dimensions and tolerances (always in millimeters). Only a snapped clip plate part 24a is shown with its reference sign, in order to illustrate its function as a position securement. The L-shaped sheet metal part 21 is made of structural steel with a thickness of 3 mm or 5 mm and is produced inexpensively as a free-falling punched part. It has a height of 116 mm or 118 mm (resulting from the different thicknesses) and a width of 69 mm. The selected width results from the application conditions of the L-shaped sheet metal parts in practice: Several L-shaped sheet metal parts are threaded onto bars of the lowest longitudinal reinforcement layer Buu (by means of carrying the bars through the recesses 50) to form a line element, which is inserted as a supplementary reinforcement between the bars of an already present lowermost reinforcing layer Buu into the basic body (reinforcement arrangement before casting with concrete) of a reinforced concrete/prestressed concrete component. The bars of the already present longitudinal reinforcement layer Buu usually have a spacing of 10 cm or 15 cm. A line element with L-shaped sheet metal parts 21 of the selected width of 69 mm can be conveniently placed in this spacing in both cases, whereby the resulting overall arrangement of the bars of the lowest longitudinal reinforcing layer Buu gets approximately equidistant bar gaps. Of course, the width of the L-shaped sheet metal part 21 can be optimized by taking the specific application conditions into account.

(20) The angled longitudinal recess 23 has a depth T=(30?1) mm. The feed channel S of the angled longitudinal recess 23 is inclined by ?=45? with respect to the horizontally extending fastening region BF, which has a length of (16?1) mm, so that the feed angle is ?=45?. A height difference HD of 14 mm is realized between the opening 29 and the fastening region BF of the angled longitudinal recess 23 of the L-shaped component 21. Via the feed channel S, the stirrup arches 34 (not shown) of one or two stirrups 30 can be pushed into the fastening region BF. The angled longitudinal recess 23 has a height of 8 mm, so that the stirrups 30 made of reinforcing bar steel with a nominal diameter of 6 mm are freely movable in the angled longitudinal recess 23.

Part 2 of the Solution: Pushing the Stirrups into the Angled Longitudinal Recesses 23 of the L-Shaped Sheet Metal Parts 21 According to the Invention

(21) Initial situation before pushing-in:

(22) A basic body for a reinforced concrete/prestressed concrete component is provided, which is equipped with the required number of L-shaped sheet metal parts 21 with an angled longitudinal recess 23 according to the invention. The L-shaped sheet metal parts 21 are connected in the manner described above with the lower longitudinal reinforcement Buu, Bu. The reinforced concrete/prestressed concrete component can be designed as a semi-precast part or as an in-situ concrete part. In case of a semi-precast part, the lower part of the basic body is already cast with concrete in the precast factory. The casting height is selected in a way so that the angled longitudinal recesses 23 for installing the stirrups 30 and the recesses 25a, 26a for the installation of the clip plate parts 24a still remain free. This is ensured in any case by a casting height of 4 cm to 6 cm. In case of an in-situ concrete component, the concrete is completely cast on the building site. The upper longitudinal reinforcement, consisting of the longitudinal reinforcement layers Boo and Bo, is already laid in both cases. The upper longitudinal reinforcement can be designed as a reinforcing mat in which the two longitudinal reinforcement layers Bo and Boo are welded together and thus the horizontal clearance R, available for installing the stirrups, can no longer be changed. This design of the upper reinforcement as a reinforcing mat is absolutely preferred because it is much faster, more precise and more cost-effective to install than single reinforcing bars.

(23) Procedure of the Pushing-in Process:

(24) For pushing-in, the stirrup legs of a prefabricated stirrup 30 of the length H.sub.B, which is selected as described above, are lowered by an operator through the upper reinforcement so that the stirrup arch 34 connecting the two stirrup legs is positioned directly in front of the opening 29 of the angled longitudinal recess 23. During lowering, the stirrup 30 is preferably held under a slight inclination angle ? against the vertical (?<10?) or even vertically. However, it is possible, as explained in more detail in example 3, to incline the stirrup 30 much more strongly if necessary, particularly to avoid a collision with a bar of the upper longitudinal reinforcement layer Bo. Due to the obliquely upwardly directed feed channel S of the angled longitudinal recess 23, its opening 29 is displaced upwards, so that the stirrup arch 34 of a more inclined stirrup 30 can also be positioned in front of the opening 29. Thus, during pushing-in the inclination angle ? of the stirrup 30 can be greater than the inclination angle ?, which the stirrup 30 takes in the end position.

(25) As soon as the stirrup arch 34 is positioned exactly in front of the opening of the angled longitudinal recess 23, a pushing force F.sub.D is exerted by the operator on the stirrup 30, which moves the stirrup arch 34 through the opening 29 of the angled longitudinal recess 23 into its feed channel S and then through the feed channel S into the fastening region BF of the angled longitudinal recess 23. Surprisingly, it was found that a small pushing force F.sub.D is already sufficient for this purpose, which is much smaller than the pulling force F.sub.Z required for pulling-in according to the state of the art. As a cause of this advantageous effect, it has been found that there is no hindering friction of the stirrup arch 34 on the upper edge of the longitudinal recess 23 during pressing-in. The stirrup arch 34 slides almost frictionless into the fastening region BF. The stirrup shoulders 32 of the stirrup 30 are then laid down on two bars of the uppermost longitudinal reinforcement Boo, whereby the stirrup 30 takes in this end position an inclination angle ? which is due to the stirrup length H.sub.B.

(26) During the entire pushing-in process, the upper part of the stirrup 30 formed by the stirrup shoulders 32 has to be moved only in a very short horizontal clearance R. A clearance R, which corresponds to the depth T of the angled longitudinal recess 23, always suffices for convenient operation. Even a smaller clearance R with a length few millimeters greater than the outer diameter of the stirrup 30, which just allows the stirrup 30 to be passed between two very close-lying bars of the upper longitudinal reinforcement layer Bo and to be inclined up to 45?, is already sufficient for pushing-in. For example, if the outer diameter of the stirrup is 8 mm (a typical value in practice), a clearance R of length 8 mm.Math.?2?12 mm is sufficient to pass the stirrup 30 inclined by 45? through the upper longitudinal reinforcement. In practice the available clearance R is always significantly larger, since the spacing between two reinforcing bars in commercially available reinforcing mats is 10 cm or 15 cm as standard. Therefore, it is always possible without difficulty to push the stirrup arches 34 into the angled longitudinal recesses 23 of the L-shaped sheet metal part 21. The selection of a short stirrup length H.sub.B ensures that the stirrup 30, after depositing its shoulders on two bars of the uppermost longitudinal reinforcement layer Boo, takes a small inclination angle ?, so that the stirrup shoulders 32 have a small lateral offset V, preferably V<5 cm. Therefore, a clearance R?5 cm is sufficient to bring the stirrup 30 into its end position. Starting from the vertical, this clearance R is always present at least in one of the two possible directions for depositing the stirrup shoulders 32. When the installation of the stirrups 30 has been completed for all L-shaped sheet metal parts 21, the reinforced concrete/prestressed concrete component is finished by casting with concrete.

(27) For the individual L-shaped sheet metal parts 21 several substantially different situations are possible during the pushing-in of the stirrups 30 due to the respective position of the bars of the upper longitudinal reinforcement Bo. They are described in the following examples.

Example 2: Above the Angled Longitudinal Recess 23 of the L-Shaped Sheet Metal Part 21 there is No Bar of the Upper Reinforcement Layer Bo

(28) In this situation shown in FIG. 3, the required horizontal clearance R is optimally positioned, i.e. directly available. A simple statistical estimate shows, that this advantageous situation is present for more than 70% of the L-shaped sheet metal parts 21. The L-shaped sheet metal part 21 shown in FIG. 3 has the dimensions indicated in FIG. 2c. A stirrup 30 of the stirrup length H.sub.B=1.03.Math.h.sub.B is used, which is 3% greater than the minimum stirrup length h.sub.B, which is in this case 16 cm. Therefore, the stirrup length H.sub.B is 16.5 cm. During the pushing-in, the stirrup arch 34 is guided via the positions 1 and 2 into the fastening region BF of the angled longitudinal recess 23 by means of the pushing force F.sub.D acting on the stirrup 30. Thereafter, the stirrup is inclined to the left into its end position 3, assuming an inclination angle ??14?. It is visible that a clearance R of about 3 cm is sufficient to push in the stirrup 30 and to place it with its stirrup shoulders 32 on two bars of the uppermost longitudinal reinforcement layer Boo. In the arrangement in FIG. 3, it is also possible to place the stirrup 30 to the right, since the necessary free space is also available. Likewise, two stirrups 30 can be pushed in, one being placed to the right, the other to the left.

Example 3: Above the Angled Longitudinal Recess 23 of the L-Shaped Sheet Metal Part 21 there is a Bar of the Upper Reinforcement Layer Bo

(29) A bar of the upper reinforcement layer Bo, which is located above the angled longitudinal recess 23 of the L-shaped sheet metal part 21, hinders the movement of the stirrup legs 32 parallel to the bars of the uppermost reinforcement layer Boo. Three corresponding situations (I, II, III) are shown in FIG. 4. In total, they are present for less than 30% of the L-shaped sheet metal parts 21. In this case, there is no optimally positioned horizontal clearance of length T above the angled longitudinal recess 23 of the L-shaped sheet metal part 21. However, horizontal clearances with a length significantly greater than T are present on both sides of the bar of the upper reinforcement layer Bo acting as an obstacle. These clearances are in the same way suitable as an optionally positioned horizontal free space for pushing-in the stirrups 30.

(30) Stirrups 30 of the minimum stirrup length h.sub.B are used which are vertical or nearly vertical in the end position. The pushing-in of the stirrups 30 is running as illustrated in FIG. 4. It is shown how to proceed at three different positions of the bar of the upper reinforcing layer Bo acting as an obstacle.

(31) In situation I, a bar of the upper reinforcing layer Bo is located vertically above the opening 29 of the angled longitudinal recess 23. FIG. 4 illustrates that the stirrup 30 of minimum stirrup length h.sub.B, by slightly tilting, passes easily the obstructive bar (stirrup position 1), its stirrup arch 34 can be pushed into the opening 29 of the angled longitudinal recess 23 and can be guided through the feed channel S (stirrup position 2) and the stirrup 30 can be brought into a vertical end position (stirrup position 3). In this end position, the stirrup arch 34 is located in the fastening region BF of the angled longitudinal recess 23, while the stirrup shoulders 32 of the stirrup 30 rest on two bars of the uppermost longitudinal reinforcement layer Boo. In this example, the stirrup 30 has an inclination angle ?=0? in the end position, while at the beginning of the pressing-in operation (stirrup position 1) it had an inclination angle ?=5?.

(32) In situation II, a bar of the upper reinforcement layer Bo is located vertically above the transition from the feed channel S into the fastening region BF of the angled longitudinal recess 23. FIG. 4 shows that a stirrup 30 of minimum stirrup length h.sub.B is also easily passed near the obstructive bar in this situation (stirrup position 1). For this purpose (compared to situation I), it must only be brought into a slightly larger inclination angle ? (here ?=17?). Its stirrup arch 34 is then pushed into the opening of the angled longitudinal recess 23 and is guided through the feed channel S (stirrup position 2) into the fastening region BF of the angled longitudinal recess. Due to the bar of the upper reinforcing layer Bo positioned above the transition from the feed channel S into the fastening region BF, the stirrup 30 cannot be brought here into an exactly vertical end position. However, it is possible to bring it into a nearly vertical end position. FIG. 4 shows that in this example already an inclination angle ?=1? is sufficient to pass the stirrup 30 by the obstructive bar of the upper reinforcement layer Bo. In order to bring the stirrup 30 into this end position, the operator only has to clamp slightly the stirrup shoulders 32.

(33) In situation II, the clear advantages of the inventive L-shaped sheet metal part 21 with an angled longitudinal recess 23 over the prior art are shown. For clarification, in FIG. 4 the same situation for an L-shaped sheet metal part 20 according to the prior art is shown. In situation II, a stirrup 30 of minimal stirrup length h.sub.B can be installed without difficulty in an L-sheet metal 21 according to the invention, since because of the obliquely upwardly directed feed channel S the opening 29 of the angled longitudinal recess 23 is reached by the stirrup arch 34 of the stirrup of minimum stirrup length h.sub.B, even if it is brought into a large inclination angle (here ?=17?).

(34) On the other hand, as shown in FIG. 4, it is not possible to install a stirrup 30 of minimum stirrup length h.sub.B in an L-shaped sheet metal part 20 according to the prior art, since such a stirrup 30 (typical nominal diameter of 6 mm) with its stirrup arch 34 pushes against the side edge of the L-shaped sheet metal part 20 and therefore it does not reach the opening 28 of the horizontally extending longitudinal recess 22 and cannot be inserted into it. It is absolutely necessary to use a longer stirrup 30 which has an undesirable, substantially greater inclination in its end position and cannot be installed when the upper longitudinal reinforcement Bo, Boo is constructed with reinforcement mats.

(35) In situation III, a bar of the upper reinforcement layer Bo is located exactly vertically above the fastening region BF of the angled longitudinal recess 23. FIG. 4 shows that it is also possible here to push the stirrup arch 34 of a stirrup 30 of minimum stirrup length h.sub.B into the opening 29 of the angled longitudinal recess 23 by inclining it even more than in situation II (here ?=19? in stirrup position 1), and then bringing the stirrup 30 into its end position (stirrup position 2). Due to the obstructive bar of the upper reinforcing layer Bo, the stirrup 30 cannot be brought into an exactly vertical end position, but takes an inclination angle ?=2.5? in the end position. Because of 1/cos 2.5??1.001, such a stirrup 30 has to have a 0.1% larger stirrup length compared to the minimum stirrup length h.sub.B. As in situation II, a stirrup 30 of minimal stirrup length h.sub.B can also be used here, since the slightly larger stirrup length can be realized by putting the shoulders of the stirrup 30 under tension by the operator. In situation III, it is also possible to install a second stirrup 30 of minimal stirrup length h.sub.B, which is, starting from the stirrup position 1, brought into its end position 2 in which it also has an inclination angle of ?=2.5? (but inclined in the opposite direction). In this example, the two stirrups 30 form an opening angle 2?=5? in their end positions 2 and 2.

(36) Thus, the objects of the invention are fully solved:

(37) A shear force reinforcement made of L-shaped sheet metal parts 21 with vertical or nearly vertical stirrups 30 of minimum stirrup length h.sub.B is provided for a reinforced concrete/prestressed concrete component. The L-shaped sheet metal parts 21 with an angled longitudinal recess 23 ensure a rapid and effort-saving installation of the stirrups 30 by pushing the stirrup arches 34 into the angled longitudinal recess 23, whereby due to the small clearance R required for pushing-in a manual movement of reinforcing bars is not required. Therefore, the upper longitudinal reinforcement can be realized by means of reinforcing mats, which can be laid quickly and cost-effectively in comparison to individual reinforcing bars.

(38) The reinforced concrete/prestressed concrete component with the shear force reinforcement according to the invention, made from L-shaped sheet metal parts 21 with vertical or nearly vertical stirrups 30 is provided particularly for use in the area of slab columns of flat slabs. It increases the punching shear resistance in the area of such slab columns.

(39) The quantitative data in this patent application, particularly regarding the dimensions of the L-shaped sheet metal part 21, are to be regarded as exemplary and not restrictive. The quantitative adaptation to L-shaped sheet metal parts with changed dimensions is possible without any problems for a person skilled in the art. Such adaptations also belong to the claimed scope of protection of the invention.

FIGURE CAPTIONS

(40) FIG. 1Schematic representation of an L-shaped sheet metal part 20 according to the prior art in the installed state and the pulling-in of a stirrup 30 into the straight longitudinal recess 22 of an L-shaped sheet metal part 20.

(41) FIG. 2a-Schematic representation of a flat component 21 with a recess A.

(42) FIG. 2b-Schematic representation of preferred embodiment of a flat component 21, designed as an L-shaped sheet metal part with an angled longitudinal recess 23, in the front view.

(43) FIG. 2c-Specific embodiment of an L-shaped sheet metal part 21 in the front, side and top view.

(44) FIG. 3Schematic representation of the pushing-in of a stirrup 30 into an angled longitudinal recess 23 of an L-shaped sheet metal part 21, in case there is no obstruction by a bar of the upper reinforcing layer Bo.

(45) FIG. 4Schematic representation of the pushing-in of a stirrup 30 into an angled longitudinal recess 23 of an L-shaped sheet metal part 21, in case there is an obstruction by a bar of the upper reinforcing layer Bo (for three different positions I, II, III of this bar, for position II as well comparison with the prior art).

(46) Note: Curvatures of the stirrup arch 34 are not shown in FIG. 4 due to a technical simplification of the drawing. In FIGS. 2b-4 the recess 25a is shown in an unsuitably wide manner. It has to be reduced to about half the width by displacing its edge adjacent the lateral edge of the flat component 21 into the interior of the flat component 21.

REFERENCE KEY

(47) 1-5temporally successive positions of a stirrup during pulling-in and pushing-in, resp. 20L-shaped sheet metal part according to the prior art 21flat component with angled longitudinal recess according to the invention, preferably designed as an L-shaped sheet metal part 22straight longitudinal recess, designed as a horizontal slot 23angled longitudinal recess, with fastening region BF and feed channel S BFfastening region Zfeed region of a straight longitudinal recess 22 Afeed region designed as a recess Sfeed channel clip plate part for notched projection 27 24a-clip plate part for notched projection 27a 25, 26recesses for snapping-in a clip plate part (at an L-sheet according to the prior art) 25a, 26a-recesses for snapping-in a clip plate part (at an L-shaped sheet metal part according to the invention) 27notched projection of an L-shaped sheet metal part 20 according to the prior art 27anotched projection of an L-shaped sheet metal part 21 according to the invention 28opening of the straight longitudinal recess 22 of an L-shaped sheet metal part 20 29opening of the angled longitudinal recess 23 30.Math.stirrup 32stirrup shoulder 34stirrup arch 40bend 50recesses just above the bend 40 Boouppermost reinforcement layer Boupper reinforcement layer (immediately below Boo) Buulowermost reinforcement layer Bulower reinforcement layer (immediately above Buu) Mcenter line of the flat component 21 Qshear force reinforcing element consisting of an L-shaped sheet metal part 20 or 21 and a stirrup (or two stirrups) 30 Rrequired clearance for pulling-in or pushing-in a stirrup into a longitudinal recess 22 and 23, respectively a-ffeeding a stirrup arch 34 under selected feed angles

FORMULA SYMBOLS

(48) H.sub.B length of stirrup h.sub.Bminimum stirrup length HDheight difference between the opening 29 of the feed channel S and the fastening region BF L.sub.BFlength of the fastening region BF of the longitudinal recess 23 L.sub.Slength of the feed channel S of the longitudinal recess 23 Tdepth of the longitudinal recess 22 or 23 ?inclination angle of a stirrup 30 against the vertical axis (stirrup in end position) ?inclination angle of a stirrup 30 against the vertical axis (while pulling and pushing, respectively) ?inclination angle of the feed channel S against the fastening region BF ?feed angle, at which a recess A allows the feeding of a stirrup arch 33 to the fastening region BF F.sub.Z pulling force when pulling on stirrups 30 F.sub.? tangential component of the pulling force F.sub.Z F.sub.? normal component of the pulling force F.sub.Z F.sub.D pushing force while pushing the stirrup 30 Vlateral offset between stirrup shoulder 32 and stirrup arch 34