Análise de edifícios de concreto armado considerando a não-linearidade física através dos processos simplificados

Abstract

This work aims to study and compare the stiffness reduction coefficients used in the nonlinear physical analysis of reinforced concrete buildings. Initially, the behavior of reinforced concrete flat frames is compared with the consideration of physical and geometric nonlinearities through a nonlinear analysis versus the simplified use of nonlinearities by reducing the stiffness of structural elements according to the NBR 6118 (ABNT, 2014), through frames already analyzed by other authors. In this initial analysis, the differences in top displacement are evidenced when the simplified analysis is used in usual reinforced concrete structures in detriment to the non-linear analysis. Subsequently, to study in more detail the influence of linearities and nonlinearities, in usual reinforced concrete buildings, an analysis is carried out using the finite element method using the CAD/TQS computer program. The purpose of this analysis was to verify the influence of the increase in the number of floors. For this, two buildings were dimensioned and verified, the first with 4 to 10 floors and the second with 15 to 20 floors, both in increments of one floor. Initially the structural elements of the buildings were dimensioned through an initial analysis considering the physical non-linearity in a simplified way. Afterwards, the CAD/TQS System “Physical and Geometric Nonlinear Gantry Tool” was used to consider non-linearities in a more refined way, determining the new EI flexural stiffness reduction coefficients. The tool uses the bending moment x curvature relationships (diagrams M x 1/r) for each section after the knowledge of the reinforcement, the acting force, cover and fck, from the initial analysis, the diagram being used for the analysis in the ultimate limit state and for the evaluation of element stiffness. The process was carried out for each increment of pavement. Finally, after nonlinear analysis, it is determined which coefficients of inertia reduction could be used in the case of using the simplified method, establishing which is the best inertia reduction factor for each structural element. The values obtained in the process are compared with the normative values in the simplified consideration.