Avaliação dos parâmetros de instabilidade global em Estruturas de concreto armado

Abstract

The current architectural projects are showing a trend towards increasingly tall and slender structures, with a reduced number of structural elements such as columns. This contributes to make the structure less rigid, impacting concerns related to stability. This work emphasizes its importance in the study of the global stability of reinforced concrete buildings, where modern society's standards lean towards more vertically oriented structures to achieve a higher land utilization rate, especially with the increase in the world's urban population. The NBR 6118 (ABNT, 2023) provides tools that assist the designer in checking the stability of a building. These tools include the global instability parameter α (alpha) and the coefficient γz (gamma-z), responsible for evaluating and classifying structures as either movable or fixed nodes, indicating the need or not to consider second-order effects. There is also the FAVt coefficient (horizontal or wind stress amplification factor) which is a parameter used by the CAD/TQS system. This study presents an analysis of buildings of different typologies, evaluating the parameters α, γz, and FAVt in the face of modifications in the structural model that can impact global stability, such as variations in the number of floors, the orientation of central pillars, and plan asymmetry. It classifies the structures as movable or fixed nodes, checking the possibility of using the approximate process of the γz parameter in structural design. The results obtained from the α, γz, and FAVt parameters will allow the classification of the structure as either fixed or movable nodes, aiming to make the structure more rigid and conducive to global stability. The conclusion drawn during this work is that the γz and FAVt parameters work similarly for symmetric structures, while for asymmetric structures, the FAVt value tends to be higher. The α and γz parameters agree on the classification of the structure as fixed or movable nodes in the study.