Role of shear reinforcements on the punching shear resistance of two-way RC slab subjected to impact loading

Abstract

• Numerical analysis of punching shear resistance of RC slab subjected to impact loading. • Impact test setup is modeled in ABAQUS/Explicit computer code. • Computational results compared with the experimental ones from literature. • Parametric study to analyze the effect of stirrups’ width, spacing, and the number of compression reinforcement bars. • Shear reinforcement was able to improve the impact resistance of slab against punching. The possibility of acting impulsive loads such as blast and impact on gravity load-carrying structural members such as slabs during their construction and service life cannot be ruled out. Studies on the response of RC slabs under impact loading are available in the literature. However, the role of the shear reinforcements in the slab under impact is not fully understood and therefore needs further investigation. The slab subjected to concentrated impact loading in the form of falling construction equipment, landslip hazards, and other similar events may cause damage through punching or perforation. Under quasi-static concentrated loading, the design parameters that contribute to the shear resistance against punching are (1) concrete strength, (2) flexural steel, and (3) shear stirrups. In this work, a three-dimensional finite element model of a square concrete slab of normal strength concrete (30.10 MPa), 1000 mm × 1000 mm × 75 mm, with tension reinforcement only (0.88 %) subjected to low-velocity drop-weight impulsive impact is developed in ABAQUS/Explicit computer code considering Concrete Damage Plasticity and Johnson-Cook models with strain rate effects and validated with the experimental results in the open literature. The nonlinear interaction between the concrete and steel reinforcements is taken into account. The drop weight is a hard steel cone frustum-headed striker/impactor with a flat impact face of a total mass of 105 kg allowed to fall from 2500 mm height, impacting the slab at its centroid. To study the effect of the shear reinforcement on the impact resistance of the slab, the shear reinforcement has been varied by varying the stirrups’ width, spacing, and the number of compression reinforcement bars while keeping the impact load and other design parameters such as concrete/steel strength, support conditions, slab thickness, span, and flexural tension steel constant. Numerical simulations are executed and the outcomes are presented in terms of displacement–time plots, damage/stress profiles, damage modes, and damage dissipation energy. The results so extracted are discussed and compared. It has been found that the increase in shear reinforcement by decreasing the spacing of the stirrups improves the impact resistance of the slab against punching.