Estudo da estabilidade global de edificações usando métodos iterativos P-Delta e computacionais na avaliação dos efeitos de segunda ordem

Abstract

Advances in concrete technology allow the execution of more slender structures, due to the high mechanical strength obtained in current concretes. Because of this slenderness, there is an amplification of the so-called second-order effects, effects arising from horizontal displacements of the structures, thus, the analysis of global stability gains great importance, since it aims at the correct evaluation of these effects. In this context, we propose the study and application of P-Delta methods to verify the possibility of their use in the study of the global stability of structures, evaluating their performance in the consideration of second order effects. Stability is understood as the ability of a given structure to remain in balance despite external disturbances. The PDelta process relates the vertical load to the horizontal displacement of the structure, working iteratively to analyze the structure in its final equilibrium state. The fictitious lateral load method and the iterative gravity load method are used as P-Delta iterative methods, in addition to the SAP2000 software as a computational and reference method, and the gamma-z normative process for classifying structures in relation to their lateral displacements. By means of examples of frames with 4, 8 and 12 flights, with different ranges of z-gamma, the iterative methods are applied and the results are compared with the responses of the SAP2000 program. The comparison is made in relation to the displacements at the top and the moments at the base of the left column of each frame. In the three examples, in both methods, we can see the evolution of the total displacements at the top, which converge to the values provided by SAP2000. In the comparison of the moments, in the same way, the answers obtained with the iterative methods are close to the answer of the SAP2000. Considering the good performance of the iterative methods, it is concluded that their use to consider secondorder effects in the analysis of global stability of structures is feasible.