超浅埋大跨度Y形柱双层地铁车站三维地震响应分析

Analysis of 3D seismic response of super-shallow and large-span Y-shaped column double-layer subway station

以北京地铁6号线新华大街站公共区Y型柱双层地铁车站为工程背景,利用FLAC3D有限差分程序数值模拟分析,研究超浅埋大跨度Y形柱双层地铁车站结构,尤其是Y形柱的地震响应特性。研究结果表明:场地土层对地震动有明显的放大作用,边墙及Y形柱上部的相对水平位移和加速度均比下部的大;在人工地震波作用下,边墙及Y形柱中板以下结构相对水平位移很小,甚至在Y形柱下方出现微弱的反拱现象;Y形柱右侧叉支竖向位移明显大于左侧位移;Y形柱叉支顶部水平应力远大于其他部位的水平应力,且左右两侧叉支的应力-时程存在明显的相互滞后现象;加速度傅里叶谱与车站埋深、输入地震动强度、地震动特性有关,其中随着车站埋深增加,加速度反应的傅里叶幅值依次减小,中低频傅里叶幅值逐渐突出并产生次主频,且次主频傅里叶幅值随着车站结构埋深的增加而逐渐增大,频谱曲线的峰点频率保持不变。

Taking Y-column double subway station of Xinhua Street Station in public areas of the Beijing Metro Line 6 as engineering background, the numerical model was developed with FLAC3D finite difference program, and the seismic response characteristics of the super-shallow and large-span Y-shaped column double-layer subway station were analyzed. The results show that the site soil has obvious amplification effect on ground motion, and the relative horizontal displacement and acceleration of the upper-part are greater than those of the lower-part on the sidewall and Y-shaped column. Under artificial wave, the relative horizontal displacement of the bottom of the side wall and Y-shaped column is very small, and the weak contra-arch phenomenon even occurs on the bottom of the Y-shaped column, For the vertical displacement, the right fork of Y-shaped column is significantly greater than that of the left. For the horizontal stress, the top of fork-branch is much greater than that of other parts, and the stress-schedule of both sides of fork-branch has an obvious hysteresis phenomenon. The acceleration Fourier spectrum relates to station depth, intensity of earthquake wave and the characteristics of seismic waves. The Fourier spectrum value gradually decreases with the increase of depth of station and the low-frequency Fourier is gradually prominent and producing sub-frequency. At the same time, with the increase of station structure buried depth, the Fourier value of hypo-primary frequency increases gradually and the peak frequency of the spectral curve remains unchanged.