CAREER: Substructure Damage Characterization for Performance-Based Earthquake Engineering

该职业发展计划反映了首席研究员的长期目标，即将岩土工程和结构工程合成为基于性能的工程有形目标，从而减少地震造成的生命和经济损失。 在基础设计中，一个极其重要但基本上没有答案的问题是，在地震荷载作用下，基础的地下部分的性能如何。只有在观察到地面以上的大量运动、邻近结构已发现地基损坏或现场土壤条件特别脆弱的情况下，才可能在地震后对下部结构元件进行观察。因此，在设计过程中，彻底了解这些地下元件损坏的严重性、程度和演变至关重要。 本研究项目旨在更好地了解桩基础的损伤特性，特别是在可液化土中的桩的应用。虽然许多研究都集中在表征土壤的非线性行为，很少有研究计划，包括土壤和结构的非线性行为。第一个目标是开发必要的实验工具，进行详细的损害评估。这项初步工作将提供一个路线图，适当的实验程序，从而有助于第二个目标，这是进行一系列的实验研究，在基础水平上的大型土桩系统。在这些实验中，将采用分阶段的方法，首先模拟自由场土壤条件，然后模拟嵌入土壤中的桩（运动“测试”），最后模拟嵌入土壤中的桩支撑其质量（惯性和运动“测试”）。这种分阶段的方法将有助于确定每种相互作用模式对桩中累积损伤的相对贡献。密集阵列的传统和先进的仪器将提供丰富的详细的动态数据，并允许PI执行第三个目标，这是开发一种方法来解释和反计算土壤阻力曲线从这些实验。这将有助于实现第四个目标，即开发和评估一个合适的数值模型的实验标本，并扩展该模型进行敏感性研究，从而获得洞察到更广泛的土壤桩系统嵌入在可液化土壤的性能。这项研究的结果将填补一个重要的空白，基于性能的地震工程基础系统。它还将提供迫切需要的改进土壤阻力功能，可用于设计实践中的桩嵌入可液化土壤的性能的精细评估。这一职业发展计划的研究和教育部分旨在相互补充和加强。教育计划包括两个主要的方法，以实现持续的互动，增长和丰富的目标：（1）教育公众和（2）弥合岩土工程和结构工程之间的差距。通过实验室实践、互动式讲习班以及网上传播和外联，对公众进行教育。通过加强课程设置，采用新的学习模式（主动学习），将研究成果引入课程，并让本科生参与研究项目，来弥合岩土工程和结构工程学科之间的差距。弥合这一差距对于更广泛地了解民用基础设施系统及其与环境、道德和政治问题的关系至关重要。实验和分析工作的整合是一个理想的方式，以确保这项研究和教育计划是有效的，让学生兴奋，促进终身学习，从而准备他们作为结构和岩土工程师的基础知识，面对令人兴奋的挑战的21世纪世纪。

This career-development plan reflects the Principal Investigator's long-term goal of synthesizing geotechnical and structural engineering into performance-based engineering tangible objectives and thus reducing life and economic losses due to earthquakes. An extremely important yet largely unanswered question in foundation design is what constitutes satisfactory performance of the below ground portion of the foundation when subjected to earthquake loading. Observation of substructure elements following an earthquake is likely only performed if substantial movement above ground is observed, neighboring structures have unveiled foundation damage, or there are particularly vulnerable soil conditions at a site. Therefore, a thorough understanding of the severity, extent, and evolution of damage to these below ground elements is critical in the design process. This research project seeks to better our understanding of the damage characteristics of pile foundations, with the particular application of piles embedded in liquefiable soils. While many studies have focused on characterizing the nonlinear behavior of soils, few research programs have included the nonlinear behavior of both soil and structure. The first objective is to develop the necessary experimental tools to conduct detailed damage assessment. This initial work will provide a roadmap for proper experimental procedures and thus assist with the second objective, which is to carry out a series of experimental studies on large-scale soil-pile systems at a fundamental level. In these experiments, a phased approach will be used, whereby the free-field soil condition is first modeled, then the pile embedded in the soil (kinematic 'test'), and finally the pile embedded in the soil supporting its mass (inertial and kinematic 'test'). This phased approach will assist in determining the relative contribution of each mode of interaction to the damage accumulated in the pile. Dense arrays of both conventional and advanced instrumentation will provide an abundance of detailed dynamic data, and allow the PI to carry out the third objective, which is to develop a methodology for interpreting and back-calculating soil resistance curves from these experiments. This will in turn help fulfill the fourth objective, which is to develop and evaluate a suitable numerical model of the experimental specimens and expand this model to perform sensitivity studies, thus gaining insight into the performance of a broader spectrum of soil-pile systems embedded in liquefiable soils.The results of this research will fill a vital gap in performance-based earthquake engineering of foundation systems. It will also provide sorely needed improved soil resistance functions that can be used in design practice for a refined evaluation of the performance of piles embedded in liquefiable soils. The research and educational components of this career-development plan are designed to complement and enhance each other. The education plan includes two primary approaches towards the objective of continued interaction, growth and enrichment: (1) educating the public and (2) bridging the gap between geotechnical and structural engineering. Educating the public is pursued through hands-on laboratories, interactive workshops, and web-based dissemination and outreach. Bridging the gap between geotechnical and structural engineering disciplines is pursued through curriculum enhancement, using new learning models (active learning), introducing research results into course lessons, and involving undergraduates in research projects. Bridging this gap is critical to developing a broader based understanding of the systems of civil infrastructure and its relationship with the environment, ethical and political issues. The integration of experimental and analytical work is an ideal way to ensure this research and education plan is effective in keeping students excited and promoting life long learning, thus preparing them as structural and geotechnical engineers with the fundamental knowledge to face the exciting challenges of the 21st century.