Procedimento para avaliação de deslocamentos de vigas de concreto armado

Abstract

A correct evaluation of deflections in reinforced concrete beams, as well as a prior analysis of the fissure zone of the concrete in tension, consist in important data in order to design reinforced concrete structures. However, theses analyses need a reasonable degree of sophistication due some complicated factors, as the material heterogeneity and the brittle concrete’s behavior under tension. The NBR 6118/2014 suggests the employment of simplified formulas to estimate instantaneous deflections of reinforced concrete beams. These formulas are based on semiempirical approaches and their employment conducts to errors when applied to beams under loadings and with restrictions different from those ones considered in the experimental work in which the formulas are based on. In this work, a purely theoretical approach is proposed to evaluate deflections of reinforced concrete beams, where the kinematic assumptions of Euler-Bernoulli beam theory are adopted. Moreover, assuming an almost static loading condition, an incremental approach is employed, where the fissure zone of the concrete in tension increases during the analysis. As a result, this approach not only enables to calculate those deflections considering the concrete’s heterogeneity and its brittle behavior under tension, but it also provides an estimative of the fissure zone of the concrete in tension. The deflections obtained by the proposed approach are compared with those ones calculated with the formulas recommended by NBR 6118/2014 and with the deflections determined by the equivalent section method. Those deflections are also compared with experimental results, showing a better agreement of the proposed approach.