Punção em lajes cogumelo : estudo da retangularidade dospilares

by Mouro, Valéria Conceição

Eight reinforced concrete square flat slabs of reinforced concrete were tested.Slabs were 130mm thick with an 1800 mm side and were submitted to central loading, andthe objective was to investigate the influence of column rectangularity coefficient. Columncross section dimensions (cmáx/cmín) varyied between 1 and 4, with a constant perimeter equal to 1000mm.Results presented and analysed include ultimate loads and failure types, modes of rupture, vertical displacements, cracking and deformations of steel and concrete. Comparisonswith codes, norms and results of literature results are also presented.The results indicate that as the rectangularity coefficient increases, punching shear resistance decreases for constant perimeter column flat slabs. Suggesting that punching shearhas to be considered specially in regions close to column extremity, where there is a larger concentration of shear forces.A proposal for an inclusion of the retangularity 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.