Punching Shear Capacity of RC Biaxial Voided Slab – Prediction by Critical Shear Crack Theory

In this study the applicability of critical shear crack theory (CSCT) to biaxial voided slab is investigated, which predicts the punching shear capacity of solid slab. Based on the experimental results of biaxial voided slab available in the literature (40 specimens) the research is carried out. The experimental results showed that the load-rotation behaviour of biaxial voided slab is remain same as that of solid slab except for specimens with void located within 0.5d from face of the column. Further, the punching shear capacity of slab specimens with voids located beyond 2d distance from column face is almost the same as that of the solid slab. Depends on the available load-rotation data modified CSCT was developed depends on the location of the void from face of the column. The predictions were observed to be very scattered with a mean and standard deviation of 0.752 and 0.412, respectively. This is reasonable as the modified CSCT estimates the capacity with respect to the location of voids and ignores the area of void at the section considered. The CSCT approach needs to be further modified by including location and area of void to predict the punching shear capacity of biaxial voided slab with reasonable accuracy.