CAREER: Substructure Damage Characterization for Performance-Based Earthquake Engineering

这个职业发展计划反映了首席研究员的长期目标，即将岩土和结构工程综合到基于性能的工程有形目标中，从而减少地震造成的生命和经济损失。地基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，什么构成地基地下部分令人满意的性能。只有在观察到地面上有明显的运动，邻近的结构已经暴露出基础损坏，或者在一个地点有特别脆弱的土壤条件时，才可能对地震后的地下结构进行观测。因此，在设计过程中，彻底了解这些地下元素的严重程度、程度和演变是至关重要的。本研究项目旨在更好地理解桩基础的损伤特征，特别是在可液化土壤中嵌入桩的应用。虽然许多研究都集中在表征土壤的非线性行为，但很少有研究项目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来进行详细的损伤评估。这项初步工作将为适当的实验程序提供一个路线图，从而有助于实现第二个目标，即在基础一级对大型土桩系统进行一系列实验研究。在这些实验中，将采用分阶段的方法，首先对自由场土壤条件进行建模，然后将桩嵌入土壤中（运动学“测试”），最后将桩嵌入支撑其质量的土壤中（惯性和运动学“测试”）。这种分阶段的方法将有助于确定每一种相互作用模式对桩内累积损伤的相对贡献。传统和先进仪器的密集阵列将提供大量详细的动态数据，并允许PI执行第三个目标，即开发一种解释和反计算这些实验中土壤阻力曲线的方法。这将有助于实现第四个目标，即开发和评估实验标本的合适数值模型，并扩展该模型以进行敏感性研究，从而深入了解可液化土壤中嵌入的更广泛的土桩系统的性能。本文的研究成果将填补基于性能的基础体系地震工程的重要空白。它还将提供急需改进的土壤阻力函数，可用于设计实践，以精确评估嵌入可液化土壤中的桩的性能。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。教育计划包括两种主要方法，以实现持续互动、成长和丰富的目标：(1)教育公众；(2)弥合岩土工程和结构工程之间的差距。教育公众是通过实践实验室、互动研讨会、网络传播和外展来实现的。通过改进课程、采用新的学习模式（主动学习）、将研究成果引入课程以及让本科生参与研究项目，弥合岩土工程和结构工程学科之间的差距。弥合这一差距对于发展对民用基础设施系统及其与环境、伦理和政治问题的关系的更广泛的理解至关重要。实验和分析工作的结合是一种理想的方式，以确保这一研究和教育计划有效地保持学生的兴奋和促进终身学习，从而使他们成为具有基础知识的结构和岩土工程师，以面对21世纪令人兴奋的挑战。

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.