Effect of opening shape, size and location on the punching shear behaviour of RC flat slabs

The current study aims to investigate the effect of opening size, location and shape on the punching shear behaviour of Reinforced Concrete (RC) flat slabs. Ten two-way slabs with a span of 1600 mm and a thickness of 120 mm were tested under a static load applied on a central stub column. The test program was divided into three groups with openings and a control slab without opening. Group I was designed to study the effect of opening size, thus, three slabs with three different opening sizes were tested. The openings dimensions were 200 × 200, 300 × 300 and 400 × 400 mm2. These openings were created beside the column. On the other hand, in group II, three slabs with the same opening size of 300 × 300 mm2 were tested, when the openings were at different locations. The distances between the opening edge and the column face were 100, 200 and 300 mm. To study the effect of opening shape, the slabs of group III having circular openings were tested. The openings’ diameters were 250, 350 and 450 mm, these values were configured to equalize the areas of the square openings of group I. The test results indicated that the slabs’ capacities and stiffness notably decreased with increasing the opening size. However, the percentage of the decrease could be reduced by increasing the distance between the column and the opening and/or using a circular opening. The ultimate experimental punching shear capacities of slabs with openings were compared with those obtained by the equations of ECP-203, ACI-318 and EC2 codes. Based on this comparison, ECP-203 and ACI-318 showed higher factors of safety than EC2.