砖石古塔水平地震作用的分析方法

Analytical method on horizontal earthquake action of ancient masonry pagoda

地震灾害是中国古塔损毁的主要因素。为了合理地评价古塔的地震作用,探讨了古塔地震分析模型的构成,以及参照现行《建筑抗震设计规范》计算地震作用时的参数确定方法;结合典型古塔的抗震分析研究,比较了振型分解反应谱法和底部剪力法所计算剪力的差异。研究表明,采用底部剪力法计算古塔的水平地震作用,可有效地简化分析工作;但所计算的基底剪力小于振型分解反应谱法的计算值,且两种方法的计算差值随着场地特征周期Tg与古塔基本周期T1的比值变小而增大。研究建议将底部剪力法采用的等效质量系数由0.85调整为1.00~0.90,对于Tg/T1值较小者取较大的等效质量系数,以保证古塔的抗震验算安全度。

Earthquake disaster is the major factor to damage ancient Chinese pagodas. To evaluate the earthquake action of ancient pagoda reasonably,this paper discusses the constituted method of seismic analysis model of ancient pagodas,as well as the parameters determination method for the earthquake action calculation referring to the active ＂Code for seismic design of buildings＂,and combined with seismic analysis of representative pagoda to compare the difference of calculated base shear that according to modal analysis response spectrum method and equivalent base shear method. The research shows that adopting equivalent base shear method to calculate the horizontal earthquake action can simplify the analysis work effectively,but the calculated base shear value is less than the value calculated by modal analysis response spectrum method,and the computational difference of the two methods is increase with the reduction of specific value of characteristic site period Tgto pagoda＇s fundamental period T1. To guarantee the degree of safety of anti-seismic checking calculation for ancient pagodas,the research suggested to adjust the equivalent mass factor of equivalent base shear method from 0. 85 to 1. 00 - 0. 90,and the larger adjustment factor is appropriate for the smaller condition of Tgto T1.