Punção em lajes cogumelo de concreto armado ‐ retangularidade dos pilares

Abstract

Eight reinforced concrete flat slabs were tested. Slabs were 1800mm square and 130mm thick and were submitted to concentric loading. The objective of this study was to investigate the influence of column rectangularity coefficient. The relationship between the column cross section dimensions (cmáx/cmín) varyied between 1 and 4 with a constant perimeter equal to 1000mm. Results presented and analyzed include ultimate loads and failure types, modes of rupture, vertical displacements, cracking and deformations of steel and concrete. Comparisons with codes and with results obtained by other researchers are also presented. The results indicate that as the rectangularity coefficient increases, punching shear resistance decreases for constant perimeter column flat slabs. This suggests that punching shear has to be considered especially in regions close to column corners, where there is a larger concentration of shear forces. A proposal for an inclusion of the rectangularity parameter (cmáx/cmín) in expressions for calculation punching shear resistance of ACI (2002), CEB‐FIP (1991), EC2 (2001) and NBR‐6118 (2003) codes is presented.