Patent Grant
10119275
The invention relates to the field of reinforced concrete and prestressed concrete structures, in particular the shear force reinforcement of reinforced concrete/prestressed concrete elements.
In reinforced concrete/prestressed concrete elements, a reliable shear force reinforcement is necessary in the region of bearing points, in particular in the region of column connections, for absorbing the shear forces occurring there due to the column forces.
DE102009056826A1 describes a reinforced concrete/prestressed concrete component with at least one upper and at least one lower longitudinal reinforcement layer and a shear force reinforcement which can absorb large shear forces and lateral forces and can be produced inexpensively as an in-situ concrete part and also as a semi-precast part. These advantageous properties are achieved by the shear force reinforcement consisting of at least 20 L-shaped sheet metal parts 20 made of structural steel, each with one or two stirrups 30, which are arranged with their stirrup arch 34 in a straight longitudinal recess 22 of the associated sheet metal part 30, whereby the shear force reinforcement is guided in its dimension over the uppermost longitudinal reinforcement layer Boo and the lowermost longitudinal reinforcement layer Buu. The horizontal longitudinal recess 22 has a feed region Z with an opening 28 suitable for the insertion of a stirrup arch 34 on a side edge of the L-shaped sheet metal part 20. Furthermore, the straight longitudinal recess 22 has a fastening region BF, in which the arches 34 are fixed by one or two stirrups 30. Both, the feed region Z and the fastening region BF, run horizontally and merge smoothly into one another.
The L-shaped sheet metal part 20 is connected to the lower longitudinal reinforcement by the L-shaped sheet metal part 20 being provided with a bend (which forms the L-shape) protruding forwards from the drawing plane and grasping the lowest longitudinal reinforcement layer Buu. In addition, two circular recesses 50 are arranged immediately above the bend 40, through which two bars of the lowest reinforcement layer Buu are guided. These two measures ensure a secure connection between the L-shaped sheet metal part 20 and the lowest longitudinal reinforcement layer Buu. The stirrup 30 resting with its shoulders on two bars of the uppermost longitudinal reinforcement layer Boo assumes an inclination angle α which can be up to 45° with respect to the vertical. In this case, the stirrup length HB is given by HB=hB/cos α, where hB is the minimum stirrup length which a vertically oriented stirrup 30 resting with its stirrup shoulders 32 on the bars of the uppermost longitudinal reinforcement layer Boo would have.
Practical tests have shown that the positioning of one or two stirrups 30 in the straight longitudinal recess 22 of an L-shaped sheet metal part 20 according to the prior art is possible only by manually pulling-in the stirrup 30 into the straight longitudinal recess 22, which is designed as a horizontal long hole. The following disadvantages related to pulling-in were identified:
It is necessary to use long stirrups 30 whose stirrup length HB is greater than the minimum stirrup length hB by a factor which can be up to √2. The material consumption for such stirrups is unnecessarily high.
In the installed state, the stirrups are very slanting at an inclination angle α against the vertical, which is up to 45°. The stirrup can therefore be installed swivelled up to 90°. Thus, there is the risk of bringing the stirrup 30 into an end position in which it is strongly deflected out of its optimum position, in which it absorbs tensile stresses in the finished reinforced concrete/prestressed concrete element (i.e., it is set under compressive stress and thus is non-functional).
The force to be applied by an operator when manually pulling in the stirrup 30 is high.
In the case of unfavorable geometrical conditions, in particular in the event of a collision with one or more bars of the upper longitudinal reinforcement layer Bo, the insertion of a stirrup 30 is only possible if, by temporarily removing this bar/these bars, a sufficiently large clearance R for pulling-in the stirrup is created. Therefore it is not possible to design the upper longitudinal reinforcement Bo, Boo in the form of reinforcement mats.
Reinforcement mats are prefabricated components, in which the bars of the two longitudinal reinforcement layers Boo and Bo are welded to a grid, i.e. are already fixed. Compared to single reinforcing bars, they can be installed much faster and more precisely. Their use is an essential prerequisite for the efficient production of reinforced concrete/prestressed concrete elements. The problems occurring during the pulling-in of the stirrup 30 according to the prior art are described in detail below and illustrated with the aid of
For this purpose,
The positioning of a stirrup 30 in its end position 5 in the straight longitudinal recess 22 of an L-shaped sheet metal part 20 runs as follows:
First, the stirrup arch 34 of the stirrup is lowered through the upper longitudinal reinforcement Boo, Bo, and positioned directly in front of the opening of the straight longitudinal recess 22 (position 1) and then subjected to a pulling force FZ, which has a tangential component F∥ directed in the longitudinal direction of the straight longitudinal recess 22. In order to form such a tangential component, the stirrup 30, starting from the vertical, has to be inclined by an angle β in the direction of the straight longitudinal recess 22 (positions 2, 3). The tangential component F∥=FZ·sin β of the pulling force FZ pulls the stirrup arch 34 into the straight longitudinal recess 22 (movement from position 3 to position 4), whereby the normal component F⊥=FZ·cos β of the pulling force FZ during the pulling-in process leads to undesired friction of the stirrup arch 34 on the upper side of the straight longitudinal recess 22. At small angles β, the desired tangential component F∥ is small, while the undesired normal component F⊥ is large, so that the operator must apply a large pulling force FZ, which leads to his rapid fatigue. The formulas F∥=FZ·sin β and F1=FZ·cos β show that it is possible to increase F∥ and reduce F⊥, by increasing the inclination angle β of the stirrup 30 during pulling-in. This is achieved by means of long stirrups 30, which can be pulled under an inclination angle β≈25° . . . 40° and occupy an inclination angle α=30° . . . 45° against the vertical in their end position. The maximum permissible stirrup length HB for such stirrups is HB=hB·√2 (for an inclination angle α=45°), this is more than 40% above the minimum stirrup length hB, combined with the corresponding additional material consumption.
When the stirrup arch 34 has reached its target position in the fastening region BF, the stirrup shoulders are laid down on two bars of the uppermost longitudinal reinforcement layer Boo. Here, the stirrup 30 reaches its end position (position 5) in which it takes the inclination angle α against the vertical.
(The relationship of FZ, F∥, F⊥ and β is shown schematically in
The stirrup legs of the stirrup 30 (i.e. the two stirrup sections which connect the two stirrup shoulders 32 to the stirrup arch 34) must be movable parallel to the bars of the uppermost reinforcement layer Boo over a very long horizontal clearance R.
In order to ensure this horizontal clearance R, no bars of the upper longitudinal reinforcement layer Bo running at right angles to the uppermost longitudinal reinforcement layer Boo can be located in its region. In
In the case of semi-precast components, this is in any case impossible because the lower section of the L-shaped sheet metal parts 20 has already been cast with concrete. Thus, the L-shaped sheet metal parts 20 with stirrups 30 attached thereto cannot be used in conjunction with an upper longitudinal reinforcement Boo, Bo made of reinforcing mats, which excludes their efficient and economical use as shear force reinforcing elements.
In their installed position, the stirrups 30 should be directed in their end position in the direction of the tensile stresses occurring in the reinforced concrete/prestressed concrete component in order to absorb these tensile stresses. These tensile stresses are inclined towards the vertical, whereby their inclination angle, which differs for the individual shear force reinforcement elements Q, is generally not known exactly. A good compromise is therefore to use vertical or nearly vertical stirrups in practice. Since these stirrups produce the connection between the L-shaped sheet metal parts 20 and the upper longitudinal reinforcement Bo, Boo on the (almost) shortest path, their stirrup lengths HB may exceed the minimum stirrup length hB only slightly, preferably by not more than 6%. However, the installation of the stirrups 30 by means of pulling-in excludes the use of short stirrups 30, which occupy a vertical (α=0) or at least nearly vertical (α<20°) end position in the finished reinforced concrete/prestressed concrete component. Therefore, the desired embodiment of a shear force reinforcement consisting of L-shaped sheet metal parts 20 with (almost) vertical stirrups 30 is not even nearly realizable.
Thus, in the prior art, there is a conflict field between the use of long stirrups which reduce the force required by an operator during pulling-in and the use of short stirrups, which are strongly preferable for the formation of an effective shear force reinforcement.
The object of the present invention is to eliminate the described disadvantages of the prior art.
This object is achieved according to the invention by a flat component 21 according to claim 1, which has a feed region designed as a recess A, by a shear force reinforcing element Q according to claim 10, by a reinforced concrete/prestressed concrete component according to claim 13 and its use according to claim 15, and by the preferred embodiments described in the dependent claims. The flat, preferably rectangular, component 21 together with at least one stirrup 30 which can be connected to the flat component 21 forms the shear force reinforcing element Q. The terms used hereinafter regarding the orientation of the flat component 21 (e.g., lower section) refer to its alignment after installation in a reinforced concrete/prestressed concrete component. The flat component 21 is provided in its lower section with at least one holding means for fastening to the lower longitudinal reinforcement of this 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 reinforcement layer Buu as well as an optional bend 40 immediately below the recess(es) 50. The optional bend 40 is designed at a right angle and serves as an additional stabilization of the flat component 21 in that it rests directly against the undersides of bars of the lowest reinforcing layer Buu positioned in the recesses 50. Owing to this additional stabilizing function, the design of the flat component 21 with a bend 40 is absolutely preferable.
The flat components 21 have a fastening region BF 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 34 of one or two stirrups 30. According to the invention, the flat components also have a feed region, which is designed as a recess A, which is connected to the fastening region BF and allows the feeding of an arch 34 to the fastening region BF in a large angular range, wherein the feed angle measured from the horizontal is variable between at least 10° and 120°, as a result of which an easier feedability of the stirrups is achieved. The recess A can be narrowed in such a way that allows the feeding of an arch 34 in a preferred angular range or at a preferred feed angle ζ.
The reinforced concrete/prestressed concrete component has an upper and a lower longitudinal reinforcement, wherein the upper longitudinal reinforcement can be implemented both in the form of individual reinforcing bars and, in a preferred embodiment, in the form of reinforcing mats, and is provided with a shear force reinforcement consisting of a suitable number of the shear force reinforcing elements Q according to the invention, which are made up of flat components 21 with stirrups 30 attached thereto which are led in their extension over the uppermost longitudinal reinforcement layer Boo and the lowermost longitudinal reinforcement layer Buu. Practical tests and simulations have shown that such a shear force reinforcement of preferably at least 20 shear force reinforcing elements Q ensures a required load bearing capacity of the reinforced concrete/prestressed concrete component.
Furthermore, the object of the invention is solved by the specification of a method in which the installation of a stirrup 30 in a flat component 21 takes place by pushing-in. In their end position, the stirrups 30 assume a small inclination angle α, which lies in the range α<20°, preferably α<10°. In the ideal case, the stirrups 30 are oriented perpendicularly in the end position (α=0). The small inclination angle α is ensured by the use of short stirrups 30, the stirrup length HB of which exceeds the minimum stirrup length hB by an amount ≤6%. Such stirrups 30 assume an inclination angle α<20 degree in the end position. The stirrup lengths HB=1.02·hB and HB=hB are particularly preferred.
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
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.
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 ζ, 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
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°≤ζ≤120°. Suitable angle ranges are 10°≤ζ≤110°, preferably 80°≤ζ≤110° (whereby the operator can see the feeding area from above and can position the stirrup more quickly and securely) and 10°≤ζ≤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°≤ζ≤50° (whereby an optimum compromise of the operator's effort and the guidability of the stirrup is achieved).
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°≤ζ≤120°. Preferred feed angles are ζ=30°, ζ=45°, ζ=60°, a particularly preferred angle is ζ=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.
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
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.
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
The feed angle ζ at which a stirrup arch 34 can be fed in, is determined in this configuration by the inclination angle γ of the feed channel S against the fastening region BF (ζ=γ). The inclination angle γ is selectable from the same range as ζ. The range 30°≤γ≤60° in which also short stirrups 30 can be reliably fed in is preferred, whereby the angles γ=30°, γ=45° and γ=60° are particularly preferred, i.e. the angles which are also preferred for ζ. The lengths LS of the feed channel S and LBF of the attachment region BF are variable relative to one another, whereby the equation LS·cos γ+LBF=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
The length LBF 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.
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 LS·sin γ 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.
In order to realize the object of the invention, a small inclination angle α of the stirrup 30 in its end position (α<20°, preferably α<10°, ideally α=0), the following considerations are useful for selecting the stirrup lengths HB:
As shown in
According to the above definition, characterizing stirrups 30 with an inclination angle α<20° in the end position as short stirrups, in the above table the stirrups 30 with stirrup length 1.00·hB≤HB≤1.06·hB are classified as short stirrups, and the stirrups with stirrup lengths HB=1.07·hB, 1.15·hB, 1.41·hB are classified as long stirrups.
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 HB=1.06·hB can be safely installed in the case of a minimum stirrup length hB=12 cm (suitable for a concrete/prestressed concrete component of approximately 24 cm thickness). In the case of a minimum stirrup length hB=30 cm (suitable for a reinforced concrete/prestressed concrete component of approximately 42 cm thickness), the lateral offset V for stirrups of the lengths HB=1.06·hB would already be too great. Stirrups of a stirrup length (HB≤1.03·hB) are required. Theoretically, it is possible to choose stirrups 30 of the minimum stirrup length hB, which are vertically directed in their end position (α=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 hB, as a fraction of these stirrups could be too short and therefore could be not installable. Stirrups 30 of the stirrup length HB=1.02·hB represent a suitable compromise. They have a small inclination angle in the end position (α=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·hB) including the minimum stirrup length hB 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.
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 HB. Thus identical L-shaped sheet metal parts 21 can be used for reinforced concrete/prestressed concrete components of different thicknesses.
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 γ=45° with respect to the horizontally extending fastening region BF, which has a length of (16±1) mm, so that the feed angle is ζ=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.
Initial situation before pushing-in:
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.
Procedure of the Pushing-in Process:
For pushing-in, the stirrup legs of a prefabricated stirrup 30 of the length HB, 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 β against the vertical (β<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 β of the stirrup 30 can be greater than the inclination angle α, which the stirrup 30 takes in the end position.
As soon as the stirrup arch 34 is positioned exactly in front of the opening of the angled longitudinal recess 23, a pushing force FD 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 FD is already sufficient for this purpose, which is much smaller than the pulling force FZ 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 α which is due to the stirrup length HB.
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·√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 HB ensures that the stirrup 30, after depositing its shoulders on two bars of the uppermost longitudinal reinforcement layer Boo, takes a small inclination angle α, 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.
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.
In this situation shown in
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
Stirrups 30 of the minimum stirrup length hB are used which are vertical or nearly vertical in the end position. The pushing-in of the stirrups 30 is running as illustrated in
In situation I, a bar of the upper reinforcing layer Bo is located vertically above the opening 29 of the angled longitudinal recess 23.
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.
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
On the other hand, as shown in
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.
Thus, the objects of the invention are fully solved:
A shear force reinforcement made of L-shaped sheet metal parts 21 with vertical or nearly vertical stirrups 30 of minimum stirrup length hB 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.
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.
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.
Note: Curvatures of the stirrup arch 34 are not shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 14166745 | Apr 2014 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/059366 | 4/29/2015 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/165982 | 11/5/2015 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 1063663 | Davis | Jun 1913 | A |
| 1492441 | Foster | Apr 1924 | A |
| 1613351 | Klinger | Jan 1927 | A |
| 1867974 | Keough | Jul 1932 | A |
| 2392337 | Perry | Jan 1946 | A |
| 2500706 | Roshko | Mar 1950 | A |
| 2525513 | Barr | Oct 1950 | A |
| 2886370 | Liebert | May 1959 | A |
| 2911819 | Austin | Nov 1959 | A |
| 3114221 | Eriksson | Dec 1963 | A |
| 3238684 | Wood | Mar 1966 | A |
| 4368506 | Rapp | Jan 1983 | A |
| 4496264 | Casey | Jan 1985 | A |
| 4644727 | Hanson | Feb 1987 | A |
| 4702045 | Fricker | Oct 1987 | A |
| 4835933 | Yung | Jun 1989 | A |
| 4854106 | Bogar | Aug 1989 | A |
| 5596846 | Kelly | Jan 1997 | A |
| 6024333 | Raasch | Feb 2000 | A |
| 6212848 | Cooper | Apr 2001 | B1 |
| D520649 | Hansort | May 2006 | S |
| 7111432 | Hansort | Sep 2006 | B2 |
| 7140307 | Wolbert | Nov 2006 | B1 |
| 7963392 | Kodi | Jun 2011 | B2 |
| 8235350 | Tetsuda | Aug 2012 | B2 |
| 8322109 | Trangsrud | Dec 2012 | B2 |
| 8650828 | Gunther | Feb 2014 | B2 |
| 8707644 | Degen | Apr 2014 | B2 |
| 8815366 | Gunther | Aug 2014 | B2 |
| 8925893 | Biedenweg | Jan 2015 | B2 |
| 20070101672 | Gunther | May 2007 | A1 |
| 20080209843 | Helms | Sep 2008 | A1 |
| 20090189036 | Foster | Jul 2009 | A1 |
| 20090217612 | Window | Sep 2009 | A1 |
| Number | Date | Country |
|---|---|---|
| 10 2009 056826 | Feb 2001 | DE |
| 2004081313 | Sep 2004 | WO |
| 2005035900 | Apr 2005 | WO |
| 2015165982 | Nov 2015 | WO |
| Entry |
|---|
| European Patent Office, International Search Report for Application No. PCT/EP2015/059366, dated Jun. 5, 2015. |
| International Searching Authority, Written Opinion of the International Searching Authority for Application No. PCT/EP2015/059366, dated Nov. 5, 2015. |
| Number | Date | Country | |
|---|---|---|---|
| 20170204606 A1 | Jul 2017 | US |
