Avaliação da estabilidade global de estruturas de pequeno porte

Abstract

The global stability assessment is one of the main steps in the analysis of the 2nd order effects on the structure. That way, in order to simplify the estimation process NBR 6118 (2014) guides the use of the α stability parameter and the 𝛾𝑍 coefficient. However, the stability parameter α only evaluates the sensitivity of the 2nd order effects. But the 𝛾𝑍 coefficient, in addition to assessing the sensitivity of the structure, also estimates the same with good approximation. Consequently, several studies in the literature evaluate the global stability in tall and slender structures, with the 𝛾𝑍 coefficient being one of the main factors used for this verification, due to its easy application. However, it has limited use in buildings with at least four floors, because of the norm's orientation in considering stiffness reducers, as an approximate form of physical non-linearity. This study has the objective to evaluate the estimate of the 2nd order effects of 𝛾𝑍 coefficient in buildings with two and three floors. As also to verify the influence of the variation of the stiffness reducers in the results of the 𝛾𝑍 coefficient. As a method of analysis, the present study used simulations of two hypothetical models in the CAD / TQS system, in which, the results of the 𝛾𝑍 coefficient, will be compared with a rigorous method of estimating the 2nd order effects, the P-∆ process. The results demonstrate that the application of less refined analyzes of the 𝛾𝑍 coefficient has less precision in the estimates of the second order effects. Since the use of 𝛾𝑍 coefficient considering the stiffness reducing indicated by the standard on 2 floors model resulted in a 𝛾𝑍 coefficient of 1.10, however when considering the process P-Δ was obtained an equal factor to 1.13. As for the models of 3 floors, the process simplified 𝛾𝑍 coefficient resulted in 1.19, and P-Δ process resulted in 1.24.