Punching shear behavior of continuous flat slabs: A new test setup incorporating system influences

Abstract

The punching shear behavior of flat slabs has been investigated in the past mainly on flat slab cutouts since experiments on continuous flat slab systems are expensive and complex. However, these cutouts represent only the hogging moment area around the slab-column connection and thus neglect system influences such as moment redistribution between sagging and hogging moment as well as compressive membrane action (CMA). Nevertheless, a few existing experiments on continuous slabs and several numerical investigations have indicated a beneficial impact of these influences on the punching shear behavior. For an experimentally verified and consistent extension of existing punching shear models as well as the derivation of more progressive design provisions, new systematic experiments with realistic depiction of these influences are needed. To investigate the punching shear behavior of continuous flat slab systems, a new test setup was developed in which isolated flat slab specimens are loaded with varying, load-dependent edge conditions. A numerical model with measured deformations as input parameters is hereby used for real-time simulation of the edge conditions such as CMA and moment redistribution based on an equivalent flat slab system. First test results and numerical calculations are very promising and confirm the positive impact of moment redistribution and CMA on the punching shear behavior due to significant higher load bearing capacities and smaller slab deformations.