Approaches for suitable modelling and strength prediction of reinforced concrete slabs.

Despite the advances on the understanding and modelling of shear and punching shear failures, the application of actual design models to some situations remains still complex. This is for instance the case when significant redistributions in the shear field may happen as for concentrated loads applied near linear supports (typical situation of deck slabs of bridges) or for continuous flat slabs supported on columns. Accounting for the potential shear field redistributions implies performing nonlinear modeling of the structure, considering both the bending and shear loss of stiffness after cracking and/or reinforcement yielding. In addition, other significant phenomena such as compressive membrane action and moment redistribution may also develop influencing the shear/punching strength. In this paper, a general methodology for analyzing the punching shear strength of continuos slabs is presented.. This is performed by using the -nonlinear finite element analysis (NLFEA) based on PARC_CL crack model. The NLFEA results - are then combined with the failure criterion of the Critical Shear Crack Theory to predict the punching shear strength of the member. The results of this approach are compared against an actual flat slab supported on 16 columns tested in EMPA (1977), showing consistent agreement and explaining the observed behavior and load redistributions. Furthermore, the influence of moment redistribution and compressive membrane action will be analyzed and compared to current codes of practice