Long-period ground motion has become an important consideration because of the increasing number of large and long-period structures.Therefore,a thorough investigation on the formation and characteristics of longperiod ground motion is desirable for engineering applications.In this work,an analytical study is performed to examine the effect of several parameters and the combining mode for equivalent harmonic components on the dynamic response of systems.The results of the work show that the harmonic components in equivalent ground motion are evidently influenced by the intensity rise time,duration,phase and combining mode.Moreover,the long-period ground motions are simplified and simulated by separate harmonic components through proper combination.The findings of the work are believed to be useful in the selection of input ground motion in structural seismic analysis.
Plan asymmetry leads to lateral-rotational coupled effects on structural response characteristics.This investigation deals with a simplified method for performance estimation of structures with asymmetric plan.By taking the eccentric characteristics of structures into account,an equivalent triple-degree of freedom (ETDOF) system,which is constructed by eccentric mass,rigid links and springs,is proposed.The modal pushover analysis (MPA) method for asymmetric plan structures is proposed.The target displacement is determined by constant strength spectrum.The applicability of proposed method is discussed.A generic mass eccentric 4-story steel frame is analyzed by the proposed MPA procedure and nonlinear time history analysis (NTHA).The results show that the maximum deformation obtained from MPA has a good agreement with the NTHA results.The proposed MPA procedure is reliable and effective for evaluating the performance of asymmetric plan structures.
