An explicit solution for the effect of earthquake incidence angles on seismic ductility demand of structures using Bouc-Wen model

Abstract

Investigating the effect of earthquake incidence angles on the seismic ductility demands of building structures is paramount for the performance-based earthquake engineering. However, previous studies were mainly devoted to assessing the effect of earthquake incidence angles for a specific building by a refined or simplified structural model via finite element method. This method prevents researchers from studying this effect thoroughly, especially for a wide range of building vibration periods. To deal with this problem, a mass with a two-degree-of-freedom (1M2DOF) system was first introduced in this study to model building structures under biaxial earthquake excitation by incorporating the biaxial Bouc-Wen-Baber-Noori (BWBN) model. Then, an explicit solution was derived in terms of governing equation of motion (GEM) to estimate the seismic ductility demands of building structures by introducing the strength reduction factors for the 1M2DOF system. To reduce the computational complexity, model parameters involved in the derived solution were further investigated, concluding that only eleven model parameters are required to vary in structural modelling. After that, the effect of earthquake incidence angles, together with the influence of structural hysteresis characteristics, strength reduction factors, and building vibration periods were investigated, respectively, demonstrating well the applicability of the derived solution. Finally, to facilitate the application in practice, the biaxial constant strength ductility demand spectra in consideration of the effect of earthquake incidence angles were established. The investigation indicated that the derived solution is beneficial for researchers to investigate the effect of earthquake incidence angles for a wide range of building structures.