Seismic response of the built environment in densely populated urban areas

地震是世界范围内工程结构的一种长期危害。对于人口密集的城市地区（城市）尤其如此，最近的大规模地震表明，建筑物的密度对地震破坏的成本具有显着的倍增效应。目前，通常的做法是确定与周围城市环境隔离的结构的地震响应。事实上，在人口稠密的市区，楼宇往往被其他建筑物所包围，而这些建筑物的设计可能相似，也可能截然不同（例如一幢40层高的楼宇紧挨着一幢5层高的楼宇）。一个城市区域与一个街区的相邻建筑物可以被认为是一个复杂的结构系统，这些结构可以通过连接它们的地面相互作用。在密集的城市环境中，结构的实际地震响应可能与使用基于孤立结构行为的当前方法预测的地震响应显著不同（并且更大）。如果相邻结构的间距足够近，并且彼此异相振动，则由于相邻结构之间的“冲击”-瞬时碰撞，随后可能发生损坏。与隔离结构相比，如果结构与结构的相互作用增加了建筑物的响应，这种情况将会恶化。此外，结构的紧密堆积/间隔也使得灾难性故障的后果更加严重，因为可能发生对相邻结构的重大附带损害。虽然以前的研究这一领域提供了很好的初步见解结构-土壤-结构相互作用的数值模拟，仍然有一些问题需要解决之前，这种知识和理解可以实际应用于密集的城市地区的工程设计。值得注意的是，这包括目前的弹性理想化的土壤行为是否是适当的，在大地震时，应变可能在非弹性范围内，以及是否已选择适当的控制参数。本建议书中所述的工作将主要包括一个物理模型试验方案，该方案将在土工离心机内的真实的土壤上建立的相邻结构的小比例模型上进行，以满足这些需求。这项工作将代表建立在真实的土壤上的结构所涉及的基本现象的第一个系统的实验研究。结果将随后被用来评估的有效性，使用现有的模型孤立的结构，以评估密集的城市地区的建筑物，并评估地震条件的范围，目前的结构-土壤-结构相互作用模型的基础上，线性弹性土壤行为是适用的。物理测试数据库还将提供一个有用的观测物理行为数据库，可用于校准未来更先进的数值模拟工作。

Earthquakes are a perennial hazard to engineered structures worldwide. This is particularly true of densely populated urban areas (cities) where recent large magnitude earthquakes have demonstrated that the density of structures has a significant multiplicative effect on the cost of seismic damage. It is common practice at present to determine seismic response of structures in isolation from the urban environment which surrounds them. In reality, buildings in densely packed urban areas are often surrounded by other structures which may either be similar in design or very different (e.g. a 40-storey building next to a 5 storey building). An urban area with a block of adjacent buildings may be considered as a complex system of structures which may interact with each other through the ground which connects them. The actual seismic response of a structure within a dense urban environment may be significantly different (and larger) to that predicted using current methods based on isolated structural behaviour. If the adjacent structures are closely enough spaced and vibrate out-of-phase with each other, damage can subsequently occur due to 'pounding' - transient collision between adjacent structures. This will be worsened if structure-to-structure interaction increases the building response compared to an isolated structure. Furthermore, the close packing/spacing of structures also makes the consequences of a catastrophic failure more critical, as significant collateral damage to the adjacent structures may occur. Although previous research into this area has provided good initial insights into structure-soil-structure interaction using numerical simulation, there remain a number of issues to be addressed before this knowledge and understanding can be practically applied to engineering design in densely-packed urban areas. Notably, this includes whether current elastic idealisations of soil behaviour are appropriate during large earthquakes when strains may be in the inelastic range, and whether the appropriate controlling parameters have been selected. The work described in this proposal will consist primarily of a programme of physical model tests to be conducted on small scale models of adjacent structures founded on real soil within a geotechnical centrifuge to address these needs. This work will represent the first systematic experimental study of the fundamental phenomena involved for structures founded on real soil. The results will subsequently be used to assess the validity of using current models for isolated structures to assess buildings in densely packed urban areas and assess the range of earthquake conditions for which current structure-soil-structure interaction models based on linear elastic soil behaviour are applicable. The database of physical test data will additionally provide a useful database of observed physical behaviour which may be used to calibrate future more advanced numerical modelling work.