Analysis on Nonlinear Seismic Response of Multi-Story Torsion-Irregular Structures

Abstract eng:
Previous earthquake disasters have shown that irregular structures tend to cause torsional damage. Although scholars all over the world have contributed much in torsion effect of structures, most code use results in linear analysis or nonlinear analysis of single storey to limit torsion effect. It is necessary to conduct nonlinear analysis on the torsion effect of multi-layer irregular structures. Moreover, centralized plasticity hinge model or segmented varying rigidity model were mostly applied in preceding studies, producing difficulty in dealing with special structure models, due to lack of test data. This problem is most significant for multidimensional hysteretic model of frame columns. The beam-column fiber element model with the method of flexibility promises a satisfactory method for multidimensional hysteretic relations. In this paper the fiber model is implemented to analyze the torsion effect of irregular structures. Three groups of 6-story irregular frame structure with different eccentricity ratios are analyzed. In line with SiteⅡ, actual earthquake records are selected as the input while bidirectional earthquake excitation is taken into account. By checking the integral response (maximum drift and maximum base shear etc.) and local response (beam-column end plasticity hinge distribution and section angle ductility) of structures, the study try to evaluate the nonlinear seismic response of multi-story torsion irregular structures, and to provide guide opinion for the seismic design. The results show that the flexibility side are subject to more severe damage than the stiffness side, and the eccentricity ratio’s increase produces deteriorating torsion effect, which could be unobvious when using linear analysis model.

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