Effect of Shape, Number, and Location of Openings on Punching Shear Capacity of Flat Slabs

Experimental evidence have proved that punching shear capacity of flat slabs deteriorate
with the presence of openings located within the critical perimeter around columns. It is understood
that this deterioration varies inversely with the distance of openings from column’s face. However,
effect of the shape of openings on punching shear capacity is not well known. This study presents
experimental results of 14 flat specimens to investigate the effects of the number (2 and 4), shape
(circular, square, and rectangular), and location (1 and 4 times of slab’s thickness from column’s face)
of openings on punching shear strength. It was found that circular openings had least influence
on punching capacity followed by square and rectangular openings, respectively. Further, placing
openings at a distance of four times the slab’s thickness from column’s face had minimal impact on
punching capacity. Further, increasing the number of openings from 2 to 4 substantially reduced
the punching capacity. An effort was made to predict the punching capacities of all specimens
using the descriptive equations of ACI 318-19 and Eurocode 2. Mean of the ratio of experimental
to analytical results and standard deviation of ACI equations were found to be more accurate than
those of Eurocode 2 predictions.