Vertical Evacuation Structures Subjected to Sequential Earthquake and Tsunami Loadings

在大地震或海啸等极端事件中，公共安全是首要关切。一次大的俯冲带地震可能会引起一场大海啸，这可能会使海岸线附近传统上仅为地震载荷而设计的基础设施受到严重破坏，并导致生命损失。在低海拔的沿海地区，在最初的地面震动和俯冲地震引发的海啸到来之间的短时间内，可能很难迅速移动到地势较高的地方。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是楼层较低的建筑物，能够抵御后续的地震需求和海啸荷载。本研究将探讨一种新的建筑结构体系，其中结构单元从桩的末端到结构的顶部是连续的。这一新系统将使用高于浪高的楼层进行疏散；较低(低于浪高)的楼层将使用连接，允许较低的非疏散楼层的墙壁和楼板在最高水位“脱离”。虽然违反直觉，但这个分离系统将减少海啸对结构的负载要求，进一步保护建筑物及其居住者。这项研究将调查结构、土壤和海啸波之间的相互作用，无论是传统的仅为地震荷载设计的系统还是新的分离结构系统。这项研究的结果将为这种新型VES提供首个同类数据，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准备就绪的材料。该项目的数据将被存档并在美国国家科学基金会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).)中公开提供尽管在日本和美国的海啸多发地区已经建造了疏散结构，但它们通常是低层建筑，避难所能力有限。相比之下，更高的建筑可以起到双重作用，比如一家较低层居住着零售或会议室的酒店，而较高的一层设计用于疏散。在地震荷载作用下，建筑物预计在最大可信事件中遭受破坏，除非场地特定，否则忽略土-结构相互作用。这种设计理念不适用于VES，VES必须设计为：(1)在最大可信地震期间保持无损，(2)在较低楼层承受考虑的最大海啸力，包括水平和垂直力，其中初步研究表明，这些海啸力需求可能是设计地震力的两到五倍，以及(3)考虑液化和冲刷引起的土壤硬度和强度的变化。这项研究将解决作为VES的连续地震和海啸危险建筑性能的基本原理，考虑土-结构-波的完全非线性相互作用。将研究两种结构体系：混凝土外墙，这是一种传统的地震荷载结构解决方案，以及一种新的结构体系，该结构体系利用连续的钢管混凝土桩柱框架，在淹没深度以下的楼层具有分离连接，并调整为在特定荷载下因静水浮力而断裂。研究活动将涉及以下内容：(1)通过计算模拟调查土壤-结构系统的基本特性；(2)利用俄勒冈州立大学的NHERI大浪水槽试验研究海啸对结构的需求；(3)利用NHERI计算建模和仿真中心的资源对海啸需求和结构-土壤响应分析进行分析耦合；(4)结合研究结果对VESS在连续地震和海啸危险荷载作用下的现状进行评估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.