Abstract: The resulting internal forces and displacements are multiplied by reduction factors to obtain the design load． This paper deals with an investigation of the elasto-plastic dynamic characteristics of the superstructure for a frame structure under horizontal seismic excitations where the pile-soil-structure interaction is considered． The results of the investigation indicate that whether or not considering the pile-soil-structure interaction in elasto-plastic seismic response analyses has a great effect on the calculation results． With the consideration of the pile-soil-structure interaction results，the column stresses have amplification on different floors of the building． Therefore，the method using reduction factors to consider the pile-soil-structure interaction is not always safe or reasonable． So the elasto-plastic seismic response should be fully taken into account in design．

Key words: dynamic characteristics, common coupling, elasto-plastic analysis, seismic response analysis, reduction coefficient

摘要： 针对某框架结构进行了在地震作用下桩-土-上部结构共同耦合作用时的上部结构弹塑性动力特性和规律的研究。结果表明: 是否考虑桩-土-上部结构共同耦合作用时的弹塑性地震反应分析对计算结果有较大的影响; 考虑桩-土-上部结构共同作用后柱应力在不同的楼层有放大现象，按折减系数方法来考虑相互作用并非总是安全和合理的，设计时应充分考虑弹塑性地震反应的影响。

关键词: 动力特性, 共同耦合, 弹塑性分析, 地震反应分析, 折减系数