Vertical Evacuation Structures Subjected to Sequential Earthquake and Tsunami Loadings

在极端事件中，如大地震或海啸，公共安全是首要考虑的问题。一次大的俯冲带地震可能会引起大的海啸，这可能会使海岸线附近建造的基础设施受到严重破坏，并导致生命损失，这些基础设施传统上只设计用于地震荷载。在低海拔的沿海地区，在最初的地面震动和俯冲地震引起的海啸到来之间的短时间内，可能很难迅速转移到较高的地方。然而，垂直疏散结构（VES）可以提供避难所，对于大量沿海人口来说，最有希望的VES是具有较低楼层的建筑物，能够抵御连续的地震需求和海啸荷载。本研究将研究一种新的结构系统，用于建筑作为一个VES，其中结构元素是连续的，从桩的末端到结构的顶部。这个新系统将使用高于海浪高度的楼层进行疏散；较低的楼层将使用连接，使较低的非疏散楼层的墙壁和楼板在最高水位时“分离”。虽然违反直觉，但这种分离系统将减少海啸对结构的负荷要求，进一步保护建筑物及其居住者。本研究将探讨仅为地震荷载设计的传统体系和新的分离结构体系的结构、土壤和海啸波的相互作用。这项研究的结果将为这种新型地震探测系统提供第一手的数据，它可以改善海啸易发地区的生命安全，并为研究人员和实践者的研究生课程和研讨会提供课程准备材料。该项目的数据将在nsf支持的自然灾害工程研究基础设施（NHERI）数据仓库（http://www.designsafe-ci.org）中存档并公开提供。虽然在日本和美国的海啸易发地区已经建立了疏散设施，但它们通常是低层建筑，庇护能力有限。相比之下，较高的建筑可以有双重用途，比如酒店的低层容纳零售或会议室，高层设计用于疏散。在地震荷载作用下，建筑物预计在最大可信事件下承受破坏，除非场地特殊，否则忽略土-结构相互作用。这种设计理念不适用于VES，它必须设计：(1)在最大的可信地震中保持无损坏，(2)在较低楼层承受最大的海啸，包括水平和垂直力，初步研究表明，这些海啸力需求可能是设计地震力的两到五倍，(3)考虑到液化和冲刷导致的土壤刚度和强度的变化。本研究将解决序列地震和海啸灾害建筑性能的基本原理，作为一个VES，考虑全非线性土-结构-波相互作用。将研究两种结构系统：外部混凝土墙，这是地震荷载的传统结构解决方案，以及利用连续混凝土填充管桩柱框架的新结构系统，该框架在淹没深度以下的楼层具有分离连接，在静水浮力的特定载荷下调整为断裂。研究活动将包括以下内容：(1)通过计算模拟研究土-结构系统的基本特征；(2)利用俄勒冈州立大学NHERI大波水槽试验研究海啸对结构的需求；(3)利用NHERI计算建模与模拟中心资源对海啸需求和结构-土壤响应分析进行解析耦合分析。(4)将研究结果结合起来，评估当前地震和海啸灾害载荷作用下VESs的设计方法，并建立新的设计方法。

In extreme events, such as major earthquakes or tsunamis, public safety is a primary concern. A major subduction zone earthquake could cause a large tsunami, which could render constructed infrastructure near the coastline, traditionally designed for only seismic loads, to be severely damaged and result in loss of life. In coastal regions at low elevations, it may be difficult to quickly move to higher ground in the short time between the initial ground shaking and the arrival of a tsunami from a subduction earthquake. However, a vertical evacuation structure (VES) could provide refuge, with the most promising VES for large coastal populations being buildings with lower stories capable of resisting the sequential earthquake demands and tsunami loads. This research will investigate a new structural system for a building to serve as a VES, where the structural elements are continuous from the end of the pile to the top of the structure. This new system will use the above-wave-height stories for evacuation; the lower (below wave) stories will use connections that allow walls and slabs of the lower, non-evacuation floors to "breakaway" at the highest water level. Although counterintuitive, this breakaway system will reduce the tsunami load demands on the structure, further protecting the building and its occupants. This research will investigate the interactions of the structure, soil, and tsunami waves for both traditional systems designed only for seismic loads and the new breakaway structural system. The results of this research will provide first-of-its kind data for this new type of VES, which can improve life safety in tsunami-prone regions and provide course-ready material for graduate-level classes and seminars for researchers and practitioners. Data from the project will be archived and made publicly available in the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot (http://www.designsafe-ci.org). Although evacuation structures have been built in tsunami-prone regions in Japan and the United States, they are typically low-rise structures with limited shelter capacity. In contrast, taller structures could serve dual purposes, such as a hotel with lower stories housing retail or conference rooms, with upper levels designed for evacuation. Under earthquake loading, buildings are expected sustain damage in the maximum credible event and, unless specific to the site, soil-structure interaction is neglected. This design philosophy would not serve for a VES, which must be designed to: (1) remain damage-free during the maximum credible earthquake, (2) sustain the maximum considered tsunami at the lower floors, including horizontal and vertical forces, where initial research shows that these tsunami force demands can be two to five times the design earthquake forces, and (3) account for changes in the stiffness and strength of the soil due to liquefaction and scour. This research will address the fundamentals of sequential earthquake and tsunami hazard building performance to serve as a VES, accounting for full nonlinear soil-structure-wave interaction. Two structural systems will be studied: exterior concrete walls, which are a traditional structural solution for seismic loads, and a new structural system utilizing continuous concrete filled tube pile-column frames with breakaway connections at the floors below the inundation depth, tuned to fracture at specific loading resulting from hydrostatic buoyancy. The research activities will involve the following: (1) investigate fundamental characteristics of the soil-structure system through computational simulation, (2) experimentally study tsunami demands on the structure using the NHERI Large Wave Flume at Oregon State University, (3) analytically couple the tsunami demand and structure-soil response analyses using the NHERI Computational Modeling and Simulation Center resources, and (4) combine the findings to evaluate current and establish new design methodologies for VESs subjected to sequential earthquake and tsunami hazard loading.