Análise da deflexão de vigas de concreto armado via resultados experimentais e segundo método de Branson

Abstract

Reinforced concrete is widely used in civil construction, so it is essential to know its characteristics to make good predictions of its behavior in structures, such as reinforced concrete beams subjected to bending stresses. In the study of immediate deflections, NBR 6118:2014 recommends the use of Branson's method (1965), this method calculates the effective moment of inertia of the structural element of a beam when it has already exceeded the cracking moment (Mr), i. e. has non-linear behavior and the equivalent stiffness is used in a simplified way. In this study, the test results of nine reinforced concrete beams subjected to bending stresses were analyzed in the laboratory of civil construction materials of UFMS (LMCC-UFMS). Afterwards, these data were analyzed by comparing them with the predicted deflection results according to the above-mentioned standard, the results presented some inconsistencies, as already predicted by Kalkan (2013), who in his work pointed out that the method adopted by the Brazilian normative proves to be inefficient for sections with reinforcement rate lower than 1%. In addition, another aspect compared was the cracking moment obtained via linear-regression of the moment-deflection graphs of the laboratory tests that presented satisfactory results in general, pointing to the efficiency of the data treatment.