Effect of Membrane Forces on Punching Shear Capacity of Flat Slabs

The paper presents the analysis of the membrane forces and moment redistribution effect on punching shear capacity of flat slabs on the area of the inner column. The previous experimental tests performed on the isolated slab specimens representing the slab-column connections are assessed by the method that uses the levels-of-approximation (LoA) approach, introduced in the fib Model Code 2010. LoA I to III are intended for design and the highest LoA IV, which uses non-linear finite element analysis (NLFEA) combined with the Critical Shear Crack Theory (CSCT) model is used for assessment and a better understanding of the punching shear phenomenon. Both, multi-layered (2D) shell and three-dimensional (3D) continuum elements were used to model the slab-column connection specimen and were found to accurately predict the structural response. The numerical model was then used to conduct a parametric study on the influence of slab continuity on punching shear resistance. The results from a non-linear analysis of continuous slab models are then compared with the punching shear resistance obtained from the code provisions. The paper will present the obtained results by the LoA method and recommendations concerning of NLFEA modelling of RC flat slabs.