双向地震动作用的拟等延性系数谱  

Pseudo-constant ductility inelastic spectra for bi-directional ground motions

作　　者：王东升[1] 李宏男[1] 王国新[1] 

机构地区：[1]大连理工大学海岸和近海工程国家重点实验室,辽宁大连116024

出　　处：《地震工程与工程振动》2004年第4期25-31,共7页Earthquake Engineering and Engineering Dynamics

基　　金：国家杰出青年基金项目(50025823)

摘　　要：首先建立了以强度折减系数表述的恢复力特性满足二维屈服面模型的理想弹塑性单质点系统(它在2个相互垂直的主轴方向上分别具有水平平动自由度)在双向地震动作用下的归一化运动方程。然后引入单向地震动作用下等延性系数的强度折减系数谱,给出了双向地震动作用的拟等延性系数谱(定义为系统分别承受双向和单向地震动作用,在同一主轴方向上的最大位移反应之比)最后通过硬土场地10组双向地震动记录拟等延性系数谱的统计平均结果,分析了结构周期、位移延性系数和阻尼等因素对谱值及结构双向地震反应的影响。结果表明,双向地震动作用与单向地震动作用相比主要增加结构较长周期方向的最大位移反应。若在基于位移的抗震设计中降低结构较短周期方向的设计位移延性系数,可在一定程度上降低双向地震动的不利影响。因定义的谱为比值形式,阻尼对其影响不大。Normalized equation of motion of the single-mass-system with two translational freedoms along its perpendicular principal axes was formulated using strength reduction factors when subjected to two dimensional ground motions. Restoring force characteristics of the single-mass two-degrees-of-freedom system were determined by two-dimensional yield-surface plasticity theory. Then constant ductility inelastic spectrum of strength reduction factors for one dimensional ground motion were introduced to the normalized equation and pseudo-constant ductility inelastic spectra for bi-directional ground motions were presented. It was defined as the ratio of the maximum displacement response in the same principal axes direction of the single-mass-system when subjected to two and one dimensional ground motions respectively. The effects of periods, displacement ductility factors and damping on spectra amplitude and bi-directional structural responses were discussed by statistic analysis of 10 recordings in two directions on hard-site. Bi-directional earthquake excitations will increase the maximum displacement response of structures in the direction with longer period as compared with one-directional one. Decreasing the target displacement ductility factor of structures in the direction with shorter period can reduce the negative effects of bi-directional ground motions on structural response in the displacement based seismic design. Damping has little influence on the pseudo-constant ductility inelastic spectra since it is defined by the ratio of the maximum displacement responses.

关 键 词：地震反应 双向地震动 弹塑性反应谱 位移延性系数 强度折减系数 

分 类 号：P315.9[天文地球—地震学] TU311.3[天文地球—固体地球物理学]