覆水场地地震反应分析

Seismic Response of Underwater Site

随着各种海洋结构物的兴建,覆水场地的地震反应逐渐成为研究热点。基于任意拉格朗日-欧拉描述,推导时变区域上的流体运动方程,给出流场、结构的接触条件和流场网格运动控制方法。对于平坦覆水场地,水平向地震动作用下,根据Couette流理论证明该类场地流体作用可以忽略;竖向地震动激励下,横向均匀场地可以通过动水压力公式准确考虑流体作用,横向非均匀场地则需要通过流固耦合方法考虑流体作用,以海底隧道为例加以说明。对于起伏场地,天然起伏场地在地震动激励下的动力反应具有明显的流固耦合特征,以三角形起伏场地为算例;结构物的兴建造成的人工起伏场地同样需要考虑流固耦合效应,以某沉管隧道在水平向地震动激励下的动力反应为算例,并根据结果初步提出该类结构物流固耦合分析的简化计算方法。

As more and more offshore structures are built, seismic response of underwater site is gradually becoming a research hotspot. Based on arbitrary Largrange-Elurian description, this paper sets out governing equations of fluid motion in time dependent domain and point out contact condition between fluid and structure domain and controlling method of mesh motion in fluid domain. For even underwater site, according to Couette flow theory, this paper proves that fluid effect can be ignored under horizontal earthquake excitation; under vertical seismic excitation, horizontal uniform site can exactly consider fluid effect with dynamic pressure formula and horizontal non-uniform site need consider fluid effect with fluid-struc- ture interaction method. Submarine tunnel is taken as an example to analyze this conclusion. For uneven site, dynamic response of natural types have distinct fluid-structure interaction feature under seismic excitation and a triangle prominence site is taken as an example. Dynamic response of manmade uneven underwater site caused by structure building also need consider fluid-structure interaction effect. And dynamic response of immersed tunnel under horizontal seismic excitation is taken as an example. Then simplified calculation method of fluid-structure interaction analysis of this type structure is set out according to resuit.