P-Delta Effect on Probabilistic Ductility Demand and Cumulative Dissipated Energy of Hysteretic System under Bidirectional Seismic Excitations

摘要

This study quantitatively investigates the influences of the P-D effect on the statistics of ductility demand and cumulative dissipated energy of a hysteretic system under bidirectional seismic excitations. An improved biaxial Bouc-Wen model incorporating the P-Delta effect as well as the strength and stiffness degradations was used to represent the hysteretic behavior of an inelastic two-degrees-of-freedom (2DOF) system. The influences of both the strength/stiffness degradation and the P-D effect on the statistics of the ductility demand and cumulative dissipated energy of the hysteretic 2DOF system were quantitatively investigated using a series of strong ground motion records. Based on the numerical results, the preferred empirical probability distribution types and prediction equations for the ductility demand and normalized cumulative dissipated energy of the hysteretic 2DOF system including the P-D effect and under bidirectional seismic excitations were recommended, while the potential statistical correlation between the ductility demand and commonly used seismic parameters were also discussed. The analyses show that the strength/stiffness degradation and P-D effect can significantly impact the probabilistic characteristics of the ductility demand and cumulative dissipated energy of a hysteretic system under bidirectional seismic excitations, especially for a system with a short natural vibration period and/or small yield strength. The ductility demand of an inelastic 2DOF system under bidirectional excitations can be approximated by the square root of the sum of squares of the ductility demands of a single-degree-of-freedom (SDOF) system under unidirectional excitation, while the normalized cumulative dissipated energy of a 2DOF system can be expressed as the approximate sum of the normalized cumulative dissipated energies of the SDOF system. (C) 2014 American Society of Civil Engineers.