Numerical study of punching shear behavior of flat slab with openings

Punching shear is a critical failure mode in reinforced concrete flat slabs, particularly when openings are located near slab–column connections, where they disrupt load transfer and intensify stress concentration. This study develops a validated nonlinear finite element model to investigate the punching shear behaviour of flat slabs with openings. The model shows good agreement with experimental results in terms of load–deflection response and failure mode, with discrepancies in ultimate load below 4%. A systematic parametric study is conducted to quantify the effects of opening location, size, and shape. The results show that openings adjacent to the column reduce the ultimate load to 166.7 kN, while increasing the distance to 50 mm and 100 mm enhances capacity by 23.86% and 24.93%, respectively. Increasing opening size leads to strength reductions of up to 12.4%, whereas circular openings exhibit higher capacity than square ones due to reduced stress concentration. The study provides a validated numerical framework and a quantitative assessment of the combined influence of opening geometry and position on punching shear behaviour, offering new insight into the governing failure mechanisms.