Vigas-parede: métodos de análise e critérios de projeto

Abstract

Deep beams are called by the Brazilian stardard NBR 6118:2014 “special structural elements”, whose nonlinear distribution of stresses and strains should be considered. Thus, Bernoulli's hypothesis can no longer be applied and, therefore, the simplified criteria often used by design softwares, based on this hypothesis, do not represent the real behavior of these beams. Thus, the engineer is responsible for the application of analysis and design methodologies appropriate to this type of structure, among which the Finite Element Method (FEM) and the Strut and Tie Method (STM) stand out. In this work, some of the beams experimentally studied by Leonhardt and Mönnig (1986) were analyzed by means of the softwares ADINA and ATENA, and two beams were dimensioned following the criteria of ACI 318-14 and ABNT NBR 6118:2014. The first beam was designed by the MBT and it was concluded that the verification criteria for STM used by both the standards are comparable, except when considered the coefficient γ_n provided by NBR 8681:2003 and NBR 6118:2014, which lead to larger areas of struts, ties and nodal regions. In addition, the minimum distributed reinforcement ratios adopted by NBR 6118:2014 are lower than those used in other international standards and those indicated in the literature as needed to guarantee the ultimate and service conditions. The second beam was additionally dimensioned by the conventional beam model and the results were compared, concluding that the classification can lead to significantly different designs.