Punching shear behavior of steel fiber‐reinforced slabs with Filigran® punching shear reinforcement

For strengthening punching shear endangered areas, both (1) punching shear reinforcement such as stirrups, headed studs or lattice girders and (2) the use of steel fiber‐reinforced concrete (SFRC) have been investigated and applied for many years. In contrast, the combination of both of these strengthening methods is way less investigated and there are mainly studies on slabs with stirrups or headed studs in combination with SFRC which show a high potential for increasing the load‐bearing capacity for the same slab geometry. Relevant investigations with other types of punching shear reinforcement in combination with SFRC are not known. In order to fill this gap, four full‐scale tests were performed on slabs made of SFRC combined with a high‐performance punching shear reinforcement (Filigran FDB). These tests are based on a plain concrete benchmark test with FDB punching shear reinforcement from the literature. The present paper describes and discusses the design, execution, key results and lessons learnt from these experimental tests. The addition of steel fibers strengthens the punching shear reinforcement, leads to smaller crack widths, and increases the ductility of the compression zone around the column. This results in significantly higher punching shear resistance. While the tested punching shear reinforcement (FDB) increases the resistance of the plain concrete benchmark test to 2.16 times the resistance of plain concrete without shear reinforcement (VRk,c), the addition of steel fibers in the tests shows resistances up to 2.79 · VRk,c. Thus, the additional increase due to the fibers was up to 30%.