Flat slabs made of reinforced concrete are supported directly on columns. The total height of the slab construction is reduced and the formwork effort is simplified because beams are done away with. This economical system can be implemented successfully with both in-situ concrete as well as prefabricated Filigran slabs with lattice girders with a top concrete layer. The provision for both applications is an efficient and ease of use punching shear reinforcement. Workers in precast plants place the lattice girders like Filigran-Punching-Shear-Reinforcement parallel to each other on the lower bending reinforcement. Then iron benders place the upper bending reinforcement directly on the upper chord on site. This easy installation minimizes collisions of the shear reinforcement with the bending reinforcement and reduces the installation time. The Filigran-Punching-Shear-Reinforcement consists of ribbed bars with a yield strength of 500 N/mm². Two various inclined bars of diameter 9 mm and three chords of diameter 10 mm are welded together.
Scientists of the University Aachen (RWTH) tested the Filigran-Punching-Shear-Reinforcement in full-scale tests on the basis of a European Common Understanding of Assessment Document (EAD). The tested reinforced concrete slabs were between180 mm and 360 mm thick. The Filigran-Punching-Shear-Reinforcement more than doubles the punching shear resistance. The German Institute for Building Technology (DIBt) approved an increased resistance factor of 2.1 in the European Technical Assessment ETA-13/0521. This factor is higher than of any other punching shear reinforcement system based on a European standard or Assessment. Furthermore, the new European Technical Assessment released 2018 offers an alternative arrangement of the shear reinforcement and the application in slabs with none predominantly static loads. For this application the fatigue resistance of the Filigran-Punching-Shear-Reinforcement is defined by a distinct S-N-curve.
The multilingual design program ProFi is easy to use and free available to everyone. The verifications as punching shear reinforcement for in situ concrete slabs and semi precast Filigran slabs are identical. The designer retains flexibility. When implementing a composite slab with a horizontal bond joint, a verification of the interface resistance by means of the Filigran-Punching-Shear-Reinforcement is proved.
In the design program, there are interfaces to various CAD programs implemented for the transfer of the design results. Several structural-analysis programs directly include a design module for the verification of the Filigran-Punching-Shear-Reinforcement.