SV波任意角度入射下地铁车站结构地震响应分析

Seismic response analysis of subway station structure under SV waves with arbitrary incident angles

地震波入射角度对地铁车站结构地震响应的影响问题已受到学者的关注和重视。SV波斜入射时存在临界角情况,超过临界角时,场地水平向运动与竖向运动的相位差会发生改变,同时在超临界角入射下场地具有较大的竖向地震作用;然而SV波超临界角入射下的这些特征对地铁车站地震响应的影响规律还未见公开报道。通过ABAQUS有限元软件,首先验证了基于频域刚度矩阵的地震动输入计算方法求解地下隧道对任意角度SV波散射问题的计算精度,然后研究了SV波0°~80°范围内入射时II类、III类、IV类场地条件下两层三跨地铁车站结构的地震响应。研究表明:在较硬的场地中,SV波超临界角入射下场地同时具有较大的水平向和竖向地震作用,这将显著增大车站中柱的轴力幅值,与垂直入射情况相比,轴力幅值最高被增大至3.28倍,同时,SV波临界角附近入射时,轴力分布显著区别于其他情况;车站中柱的弯矩与剪力最大值均出现在地震波垂直入射时,且总体上,弯矩、剪力幅值随着SV波入射角度的增大而减小;车站与周围地基的动力相互作用,对车站结构所受到的水平地震作用具有一定的增大效应,场地越软,增大效应越显著。建议将SV波垂直入射和临界角附近入射2种工况均作为地铁车站结构抗震设计的不利工况。

The influence of the incident angle of seismic wave on the seismic response of subway station structure has been paid more and more attention by scholars.There is a critical angle when SV wave is oblique incident.When the critical angle is exceeded,the phase difference between horizontal motion and vertical motion of the site will change,at the same time,the site has a large vertical earthquake action under supercritical angle incidence.However,the influence of these characteristics of SV waves on the seismic response of subway stations under supercritical angle incidence has not been reported publicly.In this paper,the finite element software ABAQUS is used to verify the accuracy of the method based on frequency-domain stiffness matrix to solve the scattering problem of SV waves from underground tunnels at any angle,then the seismic responses of two-story three-span subway station structure under Class II,Class III and Class IV site conditions when SV waves are incident in the range of 0 to 80 degrees are studied.The results show that the site has large horizontal and vertical seismic response at the supercritical angle of SV wave in a hard site,which will significantly increase the axial force amplitude of the central column of the station.Compared with the vertical incident case,the axial force amplitude increases upto 3.28 times maximum.At the same time,when the SV wave is incident near the critical angle,the axial force distribution is significantly different from other cases.The maximum moment and shear force of the central column of the station appear when the seismic wave is perpendicularly incident,and the amplitude of the moment and shear force decreases with the increase of the incident angle of SV wave.The dynamic interaction between the station and the surrounding foundation has a certain increasing effect on the horizontal earthquake action of the station structure,and the softer the site,the more obvious the increasing effect.It is suggested that the vertical incidence and the incidence near the critical angle of SV wave should be regarded as unfavorable conditions for seismic design of subway station structure.