NEESR Payload: Characterization of Dynamic Soil-Pile Interaction by Random Vibration Methods

NEESR 有效负载：通过随机振动方法表征动态土桩相互作用

• 批准号: 0936627
• 负责人: Jeramy Ashlock
• 金额: $ 9.99万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0936627&HistoricalAwards=false
• 关键词: NEESR; Payload; Characterization; Dynamic; Soil

This award is funded under the American Recovery and Reinvestment Act of 2009(Public Law 111-5).This award is an outcome of the NSF 09-524 program solicitation ''George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)'' competition. This Payload project will be led by Iowa State University (ISU) and will utilize NEES equipment from the University of California, Los Angeles and the experimental field-test setup from the NEESR-SG project entitled "Understanding and Improving the Seismic Behavior of Pile Foundations in Soft Clays" (Award #0830328). The overall goal of the project is to contribute to improved experimental and computational tools to bridge the gap between theory and observation for soil-foundation systems under realistic multi-directional loading. Despite many years of significant advances in theoretical and experimental research, significant discrepancies remain between experimental measurements and theoretical predictions of general three-dimensional dynamic pile-soil interaction. These discrepancies may be partially attributed to a host of contributing factors such as complicated soil-pile contact conditions, difficulties in performing full-scale dynamic tests, and the statistical variation of the engineering properties of soils coupled with the challenge of their in-situ measurement. Such shortcomings in current prediction capabilities can lead to unsafe under-design or costly over-design. The focus of this Payload project is to expand the existing NEES technologies and testing capabilities for characterizing dynamic soil-pile interaction, and to improve the accuracy of current analytical and computational simulation tools. Field vibration tests will be performed on piles installed in improved and unimproved soft clays to gain a fundamental understanding of the seismic response of piles in these soil conditions. Specific goals of the project are to; (1) evaluate the effectiveness of using a servo-hydraulic inertial mass shaker and broadband random excitation for characterizing the dynamic behavior of piles in improved and unimproved clays, (2) improve the efficiency of current testing techniques by combining the traditionally separate vertical and horizontal harmonic excitation cases into a single multi-modal random-vibration test with synchronous vertical and coupled horizontal-rocking motions, (3) investigate the use of an experimental technique involving chaotic impulse loading which has shown great success in scaled-model centrifuge tests, (4) compare the relative effectiveness of using sinusoidal, random and chaotic impulse excitation types for characterizing the elastodynamic response of the soil, (5) evaluate the predictive capabilities of current analytical and computational techniques against the measured responses of piles in improved and unimproved clays and develop corrections if necessary, and (6) investigate whether experimental behavior observed in recent centrifuge studies of piles in sands extends to piles in clays. This project will generate a number of practical experimental methods and a substantive database towards a more complete understanding of the fundamental behavior of dynamic soil-pile interaction. Specific tools to be developed include an innovative method for dynamic in-situ characterization of soil-pile interaction using non-destructive random vibration techniques, improved computational simulation tools to incorporate effects of pile installation and stress-dependence on the soil's shear modulus and damping, and modifications to current engineering theories which can be immediately applied in practice. In the long term, lessons learned in this project will be extended to understanding the dynamic behavior of a greater range of soil conditions as well as pile groups. The experimental and computational simulation techniques generated by this research will improve our understanding of fundamental soil-foundation-structure interaction, enabling more accurate models for foundation design and leading to improvements in earthquake hazard mitigation. This project will involve the NEES community through teleparticipation, and a web site will be created with sections tailored for disseminating the research results to K-12 students, the general public, and the earthquake engineering community. Preliminary dynamic field-tests of a pile will be incorporated into a graduate course in soil dynamics at ISU, where students will have the option of analyzing the data for credit in a term project. Data from this project will be archived and made available to the public through the NEES data repository.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。小布朗地震工程模拟网络（NEES）研究（NEESR） 该有效载荷项目将由爱荷华州州立大学（ISU）牵头，并将利用洛杉矶加州大学的NEES设备和NEESR-SG项目的实验现场测试装置，该项目名为“了解和改善软粘土中桩基的抗震性能”（奖项编号0830328）。 该项目的总体目标是促进改进的实验和计算工具，以弥合理论和观测之间的差距差距的土壤基础系统在现实的多方向负载。 尽管多年来在理论和实验研究方面取得了重大进展，但一般三维动力桩土相互作用的实验测量和理论预测之间仍然存在显着差异。 这些差异可能部分归因于一系列的影响因素，如复杂的土桩接触条件，在进行全面的动态测试的困难，以及土壤的工程特性的统计变化，再加上他们的现场测量的挑战。 当前预测能力的这种缺陷可能导致不安全的欠设计或代价高昂的过设计。 该有效载荷项目的重点是扩展现有的NEES技术和测试能力，以表征动态土-桩相互作用，并提高当前分析和计算模拟工具的准确性。 将对安装在改良和未改良软粘土中的桩进行现场振动测试，以基本了解桩在这些土壤条件下的地震反应。 该项目的具体目标是：（1）评估使用伺服液压惯性质量振动器和宽带随机激励来表征改良和未改良粘土中桩的动力特性的有效性，（2）通过将传统上分离的垂直和水平谐波激励情况组合成单个多模态随机激励来提高当前测试技术的效率，同步垂直运动和水平-摇摆耦合运动的振动试验，（3）研究混沌脉冲加载试验技术的应用，该技术在缩尺模型离心机试验中取得了巨大成功，（4）比较使用正弦的相对有效性，随机和混沌脉冲激励类型，用于表征土壤的弹性动力学响应，（5）根据改良和未改良粘土中桩的实测响应，评估当前分析和计算技术的预测能力，并在必要时进行校正，以及（6）调查最近在砂土中桩的离心研究中观察到的实验行为是否延伸到粘土中的桩。 该项目将产生一些实用的实验方法和一个实质性的数据库，以更全面地了解动力土-桩相互作用的基本行为。 具体的工具开发包括一个创新的方法，用于动态原位表征土桩相互作用，使用非破坏性随机振动技术，改进的计算模拟工具，将桩安装和应力依赖的影响，对土壤的剪切模量和阻尼，并修改当前的工程理论，可以立即应用于实践。 从长远来看，在本项目中吸取的经验教训将扩展到了解更大范围的土壤条件以及群桩的动态行为。 本研究所产生的实验和计算模拟技术将提高我们对基本土壤-基础-结构相互作用的理解，使基础设计模型更加准确，并改善地震减灾。 该项目将通过远程参与参与NEES社区，并将创建一个网站，其中包含专门用于向K-12学生，公众和地震工程社区传播研究结果的部分。 桩的初步动态现场测试将被纳入ISU土壤动力学研究生课程，学生可以选择在学期项目中分析数据以获得学分。 该项目的数据将通过NEES数据库存档并向公众提供。