Comportamento e desempenho do reforço à flexão de lajes de concreto armado através do aumento da seção na região comprimida

Abstract

The results of an experimental investigation on the behavior and performance of oneway reinforced concrete slabs strengthened in flexure are presented. The strengthening procedure consisted of a 5 centimeter concrete overlay which was subjected to loads four days after its completion. The method used for the surface preparation was handchiseled. Special attention was given to concrete mix proportions, preparation and placing. No adhesive was employed between the concrete substrate and the overlay. Three series of slabs were tested. The slabs of Series 2, before strengthening, were tested up to the prescribed service loads. Series 1 and 3 were cast at one time and hadthe geometry corresponded, respectively, to the slabs before and after the intervention. During the experiments, displacements and strains were measured. No trace of bond failure between the concrete substrate and the overlay was observed in the tests. There was a 78 % increase in the load carrying capacity of the repaired slabs with respect to the unstrengthened one (Series 1). The performance of the strenghened slabs (Series 2) showed good agreement with the slabs of Series 3 having the same geometry but cast at one time. The experimental results were also compared to theoretical values and those obtained employing the criteria of the new NBR 6118. Good correlation was also achieved.