轨道交通地下结构抗震设计相关反应加速度法分析

通过梳理轨道交通地下结构抗震设计流程,明确抗震设计方法选择的原则和依据。在阐明反应加速度法基本原理基础上,引出土层地震反应分析的一维等效线性化法,并对影响土层地震反应计算结果关键参数进行讨论。针对一维土层地震反应得到的加速度时程提出合理拟合抛物线型二阶基线方程,可以消除加速度时程长周期随机分量引起的漂移问题,经自然积分可以得到消除基线漂移的位移时程;同时阐明数值分析软件Origin Pro有效解决积分得到位移时程的基线漂移问题并得到合理位移分布的途径和方法。以北京地铁3号线体育中心站为例,详细说明反应加速度法相关各个技术环节实现的方法和结果,并指出反应加速度法或位移法所依据的土层地震反应分析和位移时程的确定具有较强专业性,应做专项咨询分析工作;只有一维土层地震反应分析获得的加速度反应谱及时程客观合理,有限元计算所需相应地震动水平的等效剪切模量才可信;积分得到的位移时程需要有效消除基线漂移影响。只有上述相关结果真实客观可信,有限元计算结果才能模拟真实的土层-地下结构地震反应。

Analysis of the Response Acceleration Method Related to the SeismicDesign of Underground Rail Transit Structures

Obtaining a proper displacement time history is the most important procedure in the seismic design of underground rail transit structures when using the response acceleration method. This paper develops a practical method for obtaining displacement time histories by effectively eliminating baseline drift difficulties. The principles and basis of choosing a seismic design method is clarified by presenting the seismic design procedure for underground rail transit structures. Based on expounding the fundamental principles of the response acceleration method, a one-dimensional equivalent linearization approach is proposed. Discussions on the parameters that influence the effectiveness and precision of the calculation results for soil seismic response are presented. For the acceleration time-history curves derived from the one-dimensional soil seismic response calculation, this paper puts forward an approach which eliminates the drifting problem induced by long period random components of acceleration by properly simulating its second-order parabolic baseline equation. Therefore, displacement time history without baseline drift can be obtained by natural integration. Meanwhile, this paper describes the procedure and approach in which the baseline drift problem in an integral displacement time history can be effectively solved by properly applying the numerical analytical software Origin Pro. Taking the Beijing Metro line 3 as an example, this paper illustrates how every pertaining technical procedure and analytical calculation in the response acceleration method can be achieved. This study emphasizes that the analysis of soil seismic response and determination of displacement time histories are relatively complicated and specialistic. Therefore, special analytical engineering consultation work should be carried out accordingly. When the acceleration response spectra and time histories acquired through the one-dimensional soil seismic response approach are objective and reasonable, then the equivalent shear modulus under different probabilities of exceedance applied in FEM are trustworthy. Furthermore, the baseline drift problem must be appropriately handled when displacement time histories are obtained by the integral method. The abovementioned pertaining results are objective and trustful, therefore, soil-underground structure seismic response can be truly simulated by FEM.