基于快速多极边界元—有限元耦合方法的沉积盆地—城市建筑群三维地震相互作用研究

In a sedimentary basin, the existence of large and dense buildings will significantly affect the propagation and scattering characteristics of seismic waves, and then modify the edge effects and the focusing effects of the seismic waves. In order to evaluate the basin effect and the urban seismic hazard more scientifically, it is urgent to study the dynamic interaction between basin and city. For the calculation scale up to tens of millions of degrees (broadband frequency), we consider making full use of the advantages of the boundary element (BEM) and the finite element method (FEM). The scattering wave field in the sedimentary basin can be modeled by using the fast multi-pole boundary element method (FMBEM); while the buildings can be modeled by the structures of bar system with concentrated mass using the finite element method (FEM). To achieve these goals, we need to establish the 3D multi-scale coupling method. Based on the optimization of the algorithm and the MPI/OpenMP hybrid parallel technique, the efficient broadband simulation of the seismic response of the basin-city system can be realized. Considering the variation of the seismic source characteristics, as well as the geometrical and material characteristics of an alluvial basin, through a plenty of parameters analysis and case study, this project strives to reveal the effect mechanism of the structure and foundation form, the spatial distribution of urban buildings on the amplifying effect of a basin. we will also aim to clarify the ground motion characteristics and spatial variation within the sedimentary basin in the urban environment, and investigate the "clusters" characteristics of the seismic response of buildings at different locations within the basin. The research results can provide new and efficient algorithms for studying the seismic response of the large-scale complex site-structures, and provide a theoretical basis for seismic zoning, urban planning, the seismic design and safety assessment of architectural structures in the basin region.

沉积盆地中大型、密集建筑群的存在会显著影响地震波传播与散射特性，进而改变盆地边缘效应及聚焦效应。为更科学地评估盆地效应及城市地震危险性，亟需开展盆地—城市动力相互作用研究。针对千万自由度计算规模（宽频），拟充分发挥边界元法和有限元法的各自优势，对沉积盆地散射波场采用快速多极边界元模拟，对建筑群采用集中质量杆系有限元模拟，建立三维多尺度耦合方法。通过算法优化及MPI/OpenMP 混合并行技术，实现盆地—城市系统地震响应宽频高效模拟。进而针对不同的震源特性和盆地几何、材料特征，通过大量参数计算及实例分析，揭示建筑群结构及基础形式、空间分布等对盆地放大效应影响机理，阐明城市环境下沉积盆地内部地震动特性及其空间变异规律，探讨盆地不同方位建筑群地震响应“集群”特征。研究成果可为复杂场地—结构（群）地震响应分析提供新的高效方法，为沉积盆地区域地震区划、城市规划、建筑抗震设防及安全评估等提供理论依据。

我国有众多城市位于沉积盆地中，且60%以上国土面积位于7度以上地震设防区域。沉积盆地中大型、密集建筑群的存在会显著影响地震波传播与散射特性，进而改变盆地边缘效应及聚焦效应。为更科学地评估盆地效应及城市地震危险性，系统开展了沉积盆地—城市密集建筑群动力相互作用研究。首先针对单相及饱和两相三维沉积盆地，发展了宽频快速多极边界元方法；针对城市区域建筑群千万自由度计算规模（宽频），建立了三维有限元-快速多极边界元(FEM-FMMBEM)耦合方法，充分发挥边界元法和有限元法的各自优势，对沉积盆地散射波场采用快速多极边界元模拟，对建筑群采用集中质量杆系有限元模拟。通过算法优化及MPI/OpenMP 混合并行技术，实现了盆地—城市系统地震响应宽频高效模拟。进而针对不同的震源特性和盆地几何、材料特征，通过大量参数计算及实例分析，对不同形状、波速结构的三维沉积盆地对地震波的宽频散射进行了量化研究，首次给出了不同形状三维沉积盆地地震响应宽频精确解答，无量纲频率达到ka=50，可满足城市区域尺度和频率要求；准确解释了实际地震中不同尺度沉积盆地的地震动空间分布差异，以及低频和高频地震动放大效应的差异机制；透彻揭示建筑群结构及基础形式、空间分布等对盆地放大效应影响机理，阐明了城市密集建筑环境下沉积盆地内部地震动特性及其空间变异规律，探讨了沉积盆地不同方位建筑群地震响应“集群”特征。另外，针对复杂场地多点地震动构造难题，提出了一种考虑地震波散射效应的多点地震动构造方法。研究成果可为复杂场地—结构（群）地震响应分析、复杂场地效应宽频模拟提供新的高效方法，为沉积盆地区域地震区划、城市规划、建筑抗震设防及安全评估等提供理论依据。项目迄今已发表重要期刊论文40篇，其中SCI检索12篇，EI检索9篇。培养优秀硕士生12名。