近断层脉冲型地震动的残余位移系数谱研究

Residual displacement coefficient spectrum for structures under near-fault pulse-like ground motions

残余位移是基于性能抗震设计过程中一项重要性能指标。为研究近断层区域脉冲型地震动下结构的残余位移计算方法,采用同时包含场地特征周期T_g与地震动脉冲周期T_p的双周期规准法(TTN),以226条脉冲型地震动为输入,对单自由度体系进行线性与非线性时程分析,通过统计分析生成了TTN残余位移系数均值谱;探讨了场地条件、结构自振周期T以及强度折减系数R与残余位移系数C_r的关系,并拟合得到了TTN残余位移系数设计谱;研究结果表明:①采用TTN方法生成的残余位移系数谱能直接体现出速度脉冲效应对长周期结构动力响应的增大作用;②T和R是影响C_r的主要参数,而不同场地条件下的TTN残余位移系数谱具有一致性,可生成统一场地谱;③提出的TTN残余位移系数设计谱数学表达形式简洁,能够反映C_r与T,R的相关性,可用于预测近断层区域结构残余位移。

Residual displacement is a vital index for performance-based seismic design.In order to study the computational method of structure’s residual displacement in near-fault region considering its velocity-pulse-like effect,a two-period-normalization(TTN)approach incorporating the site characteristic period Tg and pulse period Tp was adopted.To obtain the mean spectrum of TTN residual displacement coefficient,linear and nonlinear dynamic time history analyses on a single degree of freedom system excited by 226 groups of near-fault pulse-like earthquake records were conducted.The influence of the local site condition,natural vibration period T and structure strength reduction factor R on the residual displacement coefficient C r was discussed,and the TTN design spectrum was obtained by fitting correspondent data.The results indicate that:①The residual displacement coefficient spectrum generated by TTN method can directly reflect the amplification of pulse effect on the dynamic responses of long period structures;②T and R are major parameters that affect C r,while TTN residual displacement coefficient spectra have excellent consistency for different site conditions,which makes it possible to generate a site-unified spectrum;③The proposed TTN residual displacement coefficient design spectrum can reflect the correlation among C r and T as well as R in a concise mathematical expression and can be applied for anticipating the residual displacements of structures in near-fault region.