Analysis of reinforced concrete plates with swimmer bars as punching shear reinforcement

Abstract

Reinforced concrete flat plates are used in buildings and garages. Their design is governed by deflection at the serviceability limit state and punching shear at the ultimate limit state. A new system of punching shear reinforcement consisting of top and bottom steel cages connected through small inclined bars, called swimmer bars, was studied. The objective of the study was to evaluate this system using non-linear finite-element (FE) analysis. FE models were first calibrated based on experimental work carried out previously. A parametric study was then conducted to study the effect of the inclination angle of the swimmer bars, the number of steel pyramids and the number and location of swimmer bars. The results obtained were compared to those predicted by BS EN 1992-1-1:2004 and ACI 318-14. The results of the parametric study indicated that the optimum inclination angle of the swimmer bars was 45°. The first pyramid of swimmer bars assembly had the highest contribution to punching capacity. It was also found that the swimmer bars located at the corners were more effective than the middle bars; accordingly, middle bars could be eliminated and larger corner bars could be used. Finally, the shear legs and swimmer bars were simulated to compare their performance under punching shear.