Punching shear testing of reinforced concrete slabs, and design implications

Abstract

The paper presents results from an extensive testing programme involving a total of 30 reinforced concrete (R/C) slabs with and without shear reinforcement, subjected to a concentrated load in the middle. Shear reinforcement consists of either bent-up bars or closed stirrups. Measured punching shear strengths were compared with strengths predicted from two major design codes (the American, ACI 318, and the European, Eurocode 2), as well as from two models from the literature, the plasticity model and a recent multi-parameter empirical model. It was found that predictions by both codes were conservative in the case of slabs without shear reinforcement; Eurocode 2 and ACI 318 predictions are generally similar in this case. Less conservative predictions were found in the case of slabs with shear reinforcement, particularly in the case of Eurocode 2 that overestimated measured strengths of slabs with stirrups. The plasticity model tended to overestimate punching strength, whereas the multi-parameter empirical model gave the best overall predictions. Finally, bent-up bars appeared to be more efficient than stirrups in increasing the punching shear strength.