超长大跨结构多点激励的若干问题研究

Some issues on multi-support seismic excitation of ultra-long span structure

多点地震激励对超长大跨结构地震反应分析有重要意义,视波速是多点地震激励的重要参数,目前其确定方法尚无统一认识,并且多点地震激励分析中未考虑基础刚度对结构的影响。文章分析影响视波速取值的因素,给出了视波速的取值方法,并提出地震反应分析中考虑基础刚度的模型及基础刚度的计算方法。以某机场航站楼设计为工程背景建立计算模型,采用时程分析法进行考虑基础刚度影响的一致与多点地震激励,分析视波速以及基础刚度对超长大跨结构多点激励的影响。结果表明,视波速的大小将直接影响结构受多点激励影响的强弱,工程中应重视视波速的合理取值;基础刚度对超长大跨结构行波效应的影响由结构底部向上递减,对结构下部楼层的影响较为显著;刚性基础可能会高估多点地震激励对结构最大楼层总剪力、层间位移角以及框架柱内力的影响,而屋盖构件内力反应受基础刚度的影响不大。

Multi-support seismic excitation is crucial to seismic response analysis of ultra-long span structures. The apparent wave velocity is an important parameter for multi-support seismic excitation, and so far no unified understanding of its determination methods has been attained. Besides, in the multi-support seismic excitation analysis, the influence of the foundation stiffness on the structure is not taken into account. In this work, the factors affecting the apparent wave velocity were analyzed and the method of determining the apparent wave velocity of multi-support seismic excitation was proposed. The model and the calculation method of considering the foundation stiffness in seismic response analysis were proposed. Based on the design of one airport terminal building, a calculation model was established. The time-history analysis method was applied to studying the influences of the apparent wave velocity and the foundation stiffness on the multi-support seismic excitation of ultra-long span structure. The results show that the magnitude of the apparent wave velocity directly affects the structure under multi-support seismic excitation and the value of the apparent wave velocity shall be taken reasonably in practice;the influence of foundation stiffness on the traveling wave effect of ultra-long span structure decreases from the bottom of the structure to its upper part, and the influence of foundation stiffness on the lower floors of the structure is more significant;the rigid foundation may overestimate the effect of multi-support seismic excitations on the maximum floor shearing forces, the maximal inter-story drift angle and internal force of frame columns,but its influence on the internal forces of the roof members is not significant.