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年的《美国复苏与再投资法》（公法111-5）资助的。该奖项是NSF 09-524计划招标的结果。 该有效载荷项目将由爱荷华州立大学（ISU）领导，并将利用加利福尼亚大学，洛杉矶大学的NEES设备以及NEESR-SG项目的实验性现场测试设置，标题为“理解和改善软粘土中桩基础的地震行为”（奖励＃0830328）。 该项目的总体目标是为改进的实验和计算工具做出贡献，以弥合现实的多向负载下的理论和观察到土壤发现系统之间的差距。 尽管在理论和实验研究方面取得了多年的重大进展，但实验测量和一般三维动态桩土壤相互作用的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许多促成因素，例如复杂的土壤接触条件，进行全尺度动态测试的困难以及土壤工程特性的统计变化以及其原位测量的挑战。 当前预测能力中的这种缺陷可能导致不安全的设计不安全或昂贵的过度设计。 该有效载荷项目的重点是扩展现有的NEE技术和测试功能，以表征动态土壤 - 核孔相互作用，并提高当前分析和计算模拟工具的准确性。 将对安装在改进和未经改进的软粘土中的桩上进行现场振动测试，以获得对这些土壤条件下桩的地震反应的基本理解。 该项目的具体目标是（1）评估使用伺服液压惯性量振荡器和宽带随机激发的有效性，以表征桩在改进和未经改进的粘土中的动态行为，（2）通过将当前测试技术的效率提高，通过将传统的垂直和水平谐波测试与单个多元模型的垂直范围结合到单独的垂直和水平的速度范围内，以提高当前测试技术的效率动作，（3）调查使用涉及混乱脉冲负荷的实验技术的使用，该技术在尺度模型离心测试中表现出巨大的成功，（（4）比较使用正弦，随机和混乱的激发类型的相对有效性，以表征土壤的弹性响应和计算的预测能力，（5）评估了预测的效果，（5）如有必要，未经改进的粘土并进行校正，以及（6）研究在最近对沙子中桩的离心机研究中观察到的实验行为是否扩展到粘土中的桩。 该项目将产生许多实践方法和实质性数据库，以更完整地了解动态土壤 - 核核酸相互作用的基本行为。 要开发的特定工具包括一种创新的方法，用于使用非破坏性随机振动技术对土壤 - 核 - 核细胞相互作用的动态表征，改进的计算模拟工具，以结合桩安装的效果以及对土壤的剪切模量和抑制作用的压力依赖性，以及对当前工程理论的修改，可以在实践中立即应用。 从长远来看，该项目中学的教训将扩展到了解较大的土壤条件和桩组的动态行为。 这项研究生成的实验和计算模拟技术将提高我们对基本土壤环境相互作用的理解，从而实现更准确的基础设计模型，并改善了缓解地震危害的模型。 该项目将涉及NEES社区通过远程推理，并将通过量身定制的部分为K-12学生，公众，公众和地震工程社区而量身定制的部分。 一堆的初步动态测试将纳入ISU土壤动态研究生课程中，在该课程中，学生将可以选择分析学期项目中的信用数据。 该项目的数据将通过NEES数据存储库进行存档并提供给公众。