Experimental analysis of the influence of concrete top slab thickness and longitudinal reinforcement on the shear strength of flat slab ribs

Abstract This paper reports a study on reinforced concrete waffle flat slabs under center loading. The study variables were concrete top slab thickness (CTST) and flexural reinforcement ratio. Twelve square slabs 1800 mm wide, 1800 mm long, and 150 mm thick were produced. The specimens were tested to failure to assess their behavior throughout load application and their failure mode. None of the slabs had shear reinforcement in the ribs. The experimental findings showed that both CTST and flexural reinforcement ratio increased the stiffness and the ultimate strength of the slabs. The most significant gains were found in the slabs with higher thickness values and higher reinforcement ratios. The results of the database showed that all codes had underestimated the ultimate strength of the slabs, as they presented rather conservative values. The modified normative equations were able to reduce the coefficient of variation of the database by at least 50%.