Modelling punching shear failure at edge slab-column connections by means of nonlinear joint elements

This paper is concerned with the modelling of punching shear failure at edge columns of flat slabs without shear reinforcement. Punching failure at edge columns is much less researched than at interior columns despite typical buildings having more edge than interior columns. The paper uses nonlinear finite element analysis (NLFEA) to study the influence on punching resistance of parameters including column aspect ratio and loading eccentricity. The NLFEA is carried out using both 3D solid elements and a Joint Shell Punching Model (JSPM) which combines nonlinear shell elements with nonlinear joint elements that incorporate the failure criterion of the Critical Shear Crack Theory (CSCT). Both constant and varying loading eccentricities are investigated since near failure eccentricity at edge column connections typically reduces below that calculated with elastic analysis due to moment being redistributed from the support to span. This reduction in eccentricity is beneficial since punching resistance is shown to depend on the final loading eccentricity. Consequently, designing for punching on the basis of elastic edge column moments is overly conservative.