Strain-based strength model for direct punching shear of interior slab–column connections

A strength model was developed to predict the direct punching shear strength of interior slab–column connections without shear reinforcement. At slab–column connections damaged by flexural cracking, it was assumed that the punching shear force was resisted mainly by the compression zone of the critical section. The punching shear strength at the critical section was determined at the intersection between the shear capacity curve and the demand curve. The shear capacity was defined by the material failure criteria of concrete, addressing the effect of the slab flexural stresses on the shear stress capacity of concrete. The shear demand was defined as a shear force required to develop the flexural moment of the slab. For the application of the proposed model to design practice, a simplified strength model was also developed, introducing two modification factors involving in the size effect and non-uniform shear stress distribution. For verification, the proposed strength model was applied to existing test specimens tested by other researchers.