Shear-Strength Model for Slab-Column Connections Subjected to Unbalanced Moment

Abstract

A shear-strength model for slab-column connections without shear reinforcement was studied to predict the direct punching shear strength and the unbalanced moment-carrying capacity. Neglecting the shear contribution of a tension zone severely damaged by flexure-shear cracks, the punching shear at a critical section was assumed to be resisted mainly by the compression zone of the slab cross section. The shear strength of the compression zone was defined as a function of the compressive normal stress developed by the slab flexural action, using the material failure criteria of concrete. For the evaluation of the unbalanced moment-carrying capacity of the slab-column connections, eccentric shear strength was defined differently at each face of the critical section around the slab-column joint, considering the degree of flexural damage of the slab. For exterior slab-column connections, the proposed model was defined in the unsymmetrical critical section. The proposed model was applied to existing test specimens of interior and exterior slab-column connections, and column footings. The proposed strength model agreed well with test results.