Global Stability in Short Buildings: Validation Through Computational Modelling

Abstract

The gamma-Z coefficient is a widely utilised metric in Brazil for the assessment of global stability in large structures, particularly buildings with more than four floors, as stipulated in the Brazilian standard NBR 6118 - Design of concrete structures - Procedure (2023). The standard under discussion permits the use of stiffness reducers, with the objective of estimating the effects of physical non-linearity (PNL). The objective of this study was to analyse the effectiveness of the gamma-Z in estimating second-order effects in two- and three-storey structures, investigating how different stiffness reduction criteria impact the results. To this end, modelling and simulations were carried out using the commercial software TQS for two different structural models, discretised as space frames. Subsequent to the design of the structures, the average stiffness coefficients were obtained by processing them using the Nonlinear Physical-Geometric Frame (NLPGF). The iterative process was repeated until the coefficients converged. The gamma-Z results were then compared with those obtained using the P-delta calculation method. The research demonstrated that the adoption of more accurate stiffness reducers, replacing the conventional values of the Brazilian standard, results in a significant improvement in the estimation of second-order effects in buildings with less than four floors.