Punching shear in flat slab systems – Experimental quantification of unconsidered system influences

Due to the demand for slender and functional buildings, flat slabs are a frequently used load‐bearing element in buildings. However, the concentrated load introduction at the slab‐column connection is often the governing detail in design due to punching shear failure. Therefore, the punching shear behavior of flat slabs has been intensively studied in the past, mostly on flat slab cutouts, as the testing of flat slab systems is expensive. The investigated main characteristics of the punching shear behavior were hereby investigated and form the basis for today's design equations. However, new investigations on flat slab systems demonstrate clearly favorable influences of the system load‐bearing effect – namely compressive membrane action and moment redistributions. These phenomena lead to significant load reserves in continuous slabs and remain unconsidered in tests on flat slab cutouts. Since the design approaches are based on the available test data on cutouts, the system influences occurring in engineering practice stay disregarded. To fill the gap in experimental data deriving more advanced design approaches, a novel test setup was developed for the efficient investigation of system behavior using isolated flat slab specimens with externally applied load‐dependent loading conditions. The test program consisted of two test series with a total of 10 test specimens. The test results reveal up to 48% increased punching shear resistances going along with reduced deformations compared to isolated flat slab cutouts.