Pile Group Under Transient Impact Loading

摘要奖：CMS 97-13951 P.K.Banerjee等人，纽约州立大学水牛城分校《瞬时冲击荷载下的群桩》这项研究集中在运输和滨水建筑物在冲击过程中的主力经验，即瞬时水平荷载。这种荷载通常被传递到由群桩和/或钻孔竖井支撑的结构的基础上。桩基和钻孔竖井基础的水平荷载设计采用弹性地基梁分析来模拟这种动力荷载。在这种分析中，从桩到土的荷载卸载用“p-y”弹簧来表示，其中土的响应(p-y或力-挠度曲线)被模拟为一系列离散的非线性弹簧。尽管已对p-y曲线进行了经验修正，以考虑许多已观察到的现象，如非线性、慢循环响应、阴影区和群相互作用因素等，但从未考虑动力扰动在桩与桩之间的传播。因此，使用这些弹簧进行动态加载就有了！通过实验和分析相结合的研究得到显著的改进和充分的验证。这项研究的目的是开发和验证一种改进的分析方法，用于承受瞬时横向冲击荷载的群桩(包括钻孔竖井)的设计。研究任务包括：a)从分析和实验两方面对层状介质中群桩的瞬时冲击特性进行关键研究；b)开发改进的分析方法；c)测试和验证所提出的新方法；以及d)在数值代码中实施改进的方法。实验研究将包括分析现有的负载测试数据，以及为测试和验证改进的分析方法创建新的测试数据。这项工作将在全国范围内适用，并立即产生影响。根据这项研究的结果，可以建议对AASHTO进行修订，以包括在合理适用的设计规范中，以设计承受船舶冲击载荷的新结构。****

Abstract Award: CMS 97-13951 P. K. Banerjee et al., SUNY Buffalo "Pile Group Under Transient-Impact Loading" This research focuses on the principal force experiences in transportation and waterfront structures during impact which is transient horizontal loading. Such loads are often transmitted to the structure's foundation supported on groups of piles and/or drilled shafts. State-of-practice design for lateral loading of pile and drilled shaft foundations used beam-on-elastic-foundation analysis to model this dynamic loading. In this analysis, load shedding from a pile to the soil is represented by "p-y" springs in which the soil response (p-y or force versus deflection curves) is modeled as a series of discrete nonlinear springs. Although p-y curves have been empirically modified to take into account many of the observed phenomena such as non-linearity, slow cyclic response, shadow zones and group interaction factors, etc., the propagation of dynamic disturbance from pile-to-pile in a group has never been considered. Therefore, the use of these springs for dynamic loading has ! to be significantly improved and soundly validated by combined experimental and analytical research. The objective of this research is to develop and validate an improved method of analysis for the design of pile groups (including drilled shafts) subjected to transient lateral impact loads. The research tasks encompass: a) a critical study of the transient impact behavior of pile groups founded in layered media, both analytically and experimentally, b) development of improved methods of analysis; c) testing and validation of the proposed new methods; and d) implementation of the improved methods in a numerical code. Experimental research will involve analysis of existing load test data as well as creation of new test data for testing and validation of the improved analytical method. The work will have national applicability as well as an immediate impact. From the re sults of this study, revisions can be recommended to AASHTO for inclusion in rationally applicable design specifications for the design of new structures subjected to vessel impact loading. ****