Análise das normas de projeto quanto a contribuição da armadura de cisalhamento e da presença de furos na resistência à punção de lajes lisas de concreto armado

Abstract

For economic and constructive reasons, more and more slabs without beams are being used as structural solutions for buildings, highlighting the importance of studying these structural elements. The punching phenomenon is associated with the use of slabs without beams, since high stresses are generated in the area close to the column, which causes the punching phenomenon. The use of slabs without beams already requires specific calculations for their design that takes into account the resistant section of the slab with the presence or not of punching reinforcements, and, in addition, the presence of openings in the region close to the connection of the slab with the pillar may occur, which directly implies the reduction of this section and the resistance of the slabs. The NBR 6118 has criteria for this problem, however other international standards also present their criteria, which differ in some points with the brazilian standard. Comparing the experimental data of some researches with the last loads estimated for current standards (fib Model Code 2010: 2013, Eurocode 2: 2004, ACI-318: 2019, NBR 6118: 2014, Norma Portugesa: 2010 and CSA: 2004), this work aimed to verify the degree of accuracy of the standards regarding the estimated breaking load and the estimated breaking mode for slabs with and without reinforcement, and slabs with and without openings. Based on the observed results it was possible to conclude that the NBR 6118: 2014 standard presented satisfactory results for the estimated loads and rupture modes, being, therefore, the standard that presented estimated results closer to reality.