Effect of column size on punching behavior of flat slabs with square columns: Numerical investigation

This study investigates the punching behavior of slabs supported by square columns of various sizes at different effective slab depths. Within the research context, a finite element model of the slab-column connections is developed using ABAQUS and calibrated based on 15 test results from the literature. Subsequently, 84 slabs with square columns are simulated, and the effect of column size is assessed in terms of load-rotation behavior, shear stress distribution, cracking patterns, punching capacity, and nominal ultimate shear stress. The findings indicate that all slabs undergo brittle punching failure due to the damage near the column corner, which occurs before the ultimate shear stress is fully reached around the column perimeter. The shear stress of the slab along the column perimeter concentrates at the column corner, with this concentration being more pronounced in slabs supported by large square columns. Moreover, as the column size increases, the punching capacity consistently rises while the nominal ultimate shear stress initially decreases, with the decline of the nominal ultimate shear stress being more significant in thinner slabs. The punching capacity predicted by the finite element analysis is compared to the values derived from ACI 318-19, EC2, MC2010, and CSCT models. The findings suggest that these formulas do not adequately capture the influence of column size on punching capacity, prompting the proposal of a new formula that refines the consideration of column size effects.