考虑群桩效应的大刚度结构的地震反应分析

基于改进的Gazetas均质土中桩-土-结构相互作用三步法计算模式,引入轴向力影响导出了一种计算层状介质中动力相互作用的新方法,扩展了群桩-土相互作用简化法的应用范围。在考虑群桩效应的基础上,对两种规范未要求进行共同作用计算的新型大刚度高层结构(带交叉斜撑的钢管混凝土框架结构和配筋砌块砌体剪力墙结构)进行了群桩-土-上部结构体系的地震反应分析。分析表明,引入群桩运动相互作用后的一体化抗震设计,可以从量化和定性两方面来较为简捷、准确地预估体系的共同作用效应程度,而按一般概念上的单纯根据位移的增大或加速度的减少来判别共同作用的产生大小是不合理的。配筋砌块砌体剪力墙结构在一定的桩土条件下反而会有更强的动力相互作用效应。上述两种新型结构都应纳入规范考虑上下部共同作用的结构体系的范畴。最后,提出了一个可以综合考虑多项影响参数的量化判别公式,可以快速判别群桩-土-上部结构是否需要开展相互作用的计算。

SEISMIC RESPONSE ANALYSIS OF LARGE STIFFNESS STRUCTURES CONSIDERING PILE-GROUPS EFFECTS

Based on the terms of Gazetas's three-step procedure for pile-soil-structure interaction in homogenous media, a new method is proposed for calculating the dynamic interaction factors of layered-soil with axial load,under harmonic or horizontal seismic excitations, and the simplified scheme for the interaction of pile-groups and soil is extended.The seismic response analysis of two tall buildings of large siffness (concrete-filled steel tubular braced frame structure and reinforced masonry shear wall structure),though no interactive computation is required in the code,is carried out considering pile-groups effects.The analysis demonstrates that the interactive effect could be easily and accurately predicted by using way of merely a qualitative or quantitative method in a systematic seismic design,after the kinematic interaction of pile-groups is taken into account.The general using way of merely evaluating displacement increase or acceleration decrease may not be rational.Furthermore,due to the various contributions of pile-soil foundations,more significant dynamic interaction effect would be generated for reinforced masonry shear wall structures.An appraisal formula considering several influencing parameters is presented to quickly assess whether pile-supported-structure dynamic interaction needs to be considered.