Análise comparativa do dimensionamento à flexão normal simples em seções retangulares considerando as tensões no concreto com distribuição retangular e parábola retângulo

Abstract

The design of rectangular sections of concrete structures subjected to simple normal bending, ensuring their safety in relation to the ultimate limit state, has been the subject of study by several authors. According to NBR 6118:2018, the distribution of concrete stresses in the section is done according to the parabola-rectangle diagram and its replacement is allowed for a simplified rectangular diagram. This study compares the two calculation models, the first called rectangular parabola, where the distribution of efforts in the rectangular cross section follows a parabola plus rectangle pattern, and the second, the simplified rectangular, which follows a rectangular pattern constant tension acting until the depth y, in accordance with the basic hypotheses provided for in item 17.2 of NBR 6118:2018. Analyzing the efforts and behavior of the structure and its deformations, it is proposed to verify for each deformation domain, subjected to simple normal bending, up to where the two models are equivalent, aiming at calculating the tensioned reinforcement area. The approach used will be the stress analysis, assuming, for each deformation domain, increasing values for the requesting external moment, and for each value of the depth of the neutral line, calculate the internal resultant of compression in the concrete and finally the value area of tensioned reinforcement. These values will be tabulated and plotted in graphs, both for the rectangular parabola model and for the simplified rectangular model, to analyze the equivalence between them.