Esforços de segunda ordem global de torção em edifícios altos em concreto armado: análise da aplicação do coeficiente de simplificação 𝜸�θ

Abstract

The study of the global stability of tall reinforced concrete buildings has been subject of extensive research on the structural desing field, resulting in significant advances in this area. The simplification coefficient 𝛾𝑍, presented by Franco e Vasconcelos (1991), became remarkable, but its limitation to determine only the translational effects of structures led Franco (2003) to introduce another simplified method, this time represented by the simplification coefficient 𝛾𝜃, which has the purpose of assessing the structures’ sensibility to global torsional effects. However, there is limited research on this subject available in the literature of the field, fact that highlights the need of further investigations on the topic. The main objective of the present study is to analyze the accuracy of applying this coefficient to quantify the global second-order effects due to the torsion of the building. The metodology was based on the modeling of four 20- story buildings on the software TQS v24, which were taken from Moser’s (2022) dissertation. In the occasion, the referred author analyzed the influence of geometric and load asymmetries on the torsional effects of the structures, with assistance from the software SAP2000. Initially, the center of torsion of the proposed models was defined by the application of the graphic method, also introduced by Franco (2003). Thereafter, the value of the simplification coefficient 𝛾𝜃 was assessed for each of the horizontal load cases. This assessment enabled its implementation to enhance the global first-order torsional effects, ultimately achieving the total horizontal displacement of the structure. Finally, it was conducted the comparative analysis between the horizontal displacement obtained through the application of the aformentioned process, the values found by Moser (2022) with the assistance of the software SAP2000 and ultimately by the iterative process P-Δ. After the analysis, it was verified that the differences between the calculation methods implemented by the softwares TQS and SAP2000 are so pronounced that they turn the comparative analysis unfeasible, at least when the matter is the horizontal displacements. On the other hand, when compared with the iterative process P-Δ, it was observed that the simultanous application of the simplification coefficients 𝛾𝑍 and 𝛾𝜃 is proven to be effective in certain situations. However, there are some limitations to its use, requiring the adaptation of certain variables to ensure that the results are consistent with reality.