Numerical modeling of optimized shear reinforcement inclination to improve ductility and punching shear capacity in RC slabs

Abstract This study explores the interaction between shear reinforcement and inclined shear crack surfaces to identify the optimal shear reinforcement inclination for enhancing the ductility and punching shear resistance of flat slab-column connections. Finite element simulations were conducted using ABAQUS/Explicit, considering shear reinforcement inclinations of 30°, 45°, 60°, and 90° relative to the horizontal plane. The analysis also examined the influence of varying flexural reinforcement ratios on punching shear behavior. The finite element model was validated using experimental data from the literature to ensure reliability. Results showed that shear reinforcement inclined at 30° and 45° significantly improved both ductility and punching shear capacity compared to vertically placed shear reinforcement. Specifically, two rows of shear reinforcement at a 30° angle increased punching load capacity by 2.8% and displacement by 26.1%, while 45° shear reinforcement improved capacity by 5.6% and displacement by 47.8%. These enhancements are attributed to the shear reinforcement aligning nearly perpendicular to the inclined shear cracks, enabling more effective crack interception. Conversely, shear reinforcement at steeper angles (60° and 90°) increased the punching shear capacity due to higher flexural reinforcement but reduced ductility. Overall, the study highlights the importance of shear reinforcement orientation in balancing strength and ductility in flat slab systems.