NEESR-II: Towards Developing an Engineering Procedure for Evaluating Building Performance on Softened Ground

摘要最近的地震提供了无数的液化破坏性影响的例子。 观察建筑物的性能，包括建筑物穿孔，轴承故障，和建筑物的横向移动。 虽然已经学到了很多东西，但在评价这些案例历史方面存在很大的不确定性，这妨碍了反分析和改进分析方法的发展。 不确定性的主要来源是地面运动的特性，缺乏液化、地面破坏和建筑物性能的顺序的文件记录，以及地面条件的固有可变性。 在地震测试中，可以仔细跟踪输入运动、地面条件和地面/结构响应，然后对这些模型进行高级反分析，这有助于提高专业人员对地面破坏及其对结构的影响的理解。 通过本研究，利用美国加州大学戴维斯分校的大型离心机，开发了一系列有据可查的经历严重和中度地面破坏的建筑物周围场地的模型“案例历史”。 土-地基-结构-相互作用是NEESR研究的一个关键优先事项，通过在各种地面条件下对不同建筑系统进行离心测试来解决。 这是para-mount的重要性，因为地面故障似乎是由于上覆结构的动态响应的一部分，和建筑物的损坏显然与地面响应。 此外，在这些实验中，将探讨对淤泥的地震响应知之甚少，而不是在过去十年中继续努力，在离心实验中只测试干净的均匀砂。 将探讨可液化土层厚度及其密度的相对重要性，同时研究不同建筑物和地基条件对可液化土层和建筑物性能的相互影响。作为该项目的一部分，创建了一个重点突出的“学生地震工程研讨会”（SEES），面向高中生，重点是少数民族学生。 外展计划利用了一种在北方加州过去43年来对科学工作很有效的策略。 许多高中生已经参加了学校的科学展览会。 通过引导他们的兴趣和他们的教师对地震减灾中涉及的挑战性问题的兴趣，我们可以激发下一代地震工程师和科学家。正如NRC（2003年）所强调的，“NEES应用于超越自由场液化的预测，进入下一个层次，即预测变形的能力......对于结构…通过考虑建造特征附近土壤强度损失的时间、顺序和位置。“实现这一目标的第一步是产生有据可查的液化地面上建筑物反应的“案例历史”，这些精心进行的离心模型试验将实现这一目标。 这些说明性的模型研究也将为应急管理人员和教师提供一个戏剧性的替代方案，以目前现有的倾斜建筑物的静态图片。 增加了动画测量响应数据的视频剪辑将使液化的地震危险及其对建筑物的影响变得生动起来。

ABSTRACTRecent earthquakes have provided countless examples of the damaging effects of liquefaction. Ob-servations of building performance included building punching, bearing failure, and lateral shifting of buildings. Although much has been learned, significant uncertainty exists in the evaluation of these case histories, which has hampered back-analyses and the development of improved analytical methods. Key sources of uncertainty are the characteristics of the ground motions, lack of documentation of the se-quence of liquefaction, ground failure and building performance, and the inherent variability of ground conditions. Centrifuge testing, where the input motion, ground conditions, and ground/structural response can be carefully tracked, followed by advanced back-analyses of these models are warranted to advance the profession's understanding of ground failure and its resulting impact on structures. Through the proposed research, a series of well documented model "case histories" of building per-formance at sites undergoing severe and moderate ground failure are developed by using the UC Davis large centrifuge. Soil-foundation-structure-interaction is a key NEESR research priority that is addressed through this centrifuge testing of different building systems on various ground conditions. It is of para-mount importance, because ground failure appeared to be caused in part due to the dynamic response of the overlying structures, and building damage was clearly linked to ground response. Additionally, the poorly understood seismic response of silt will be explored in some of these ex-periments, as opposed to continuing efforts over the past decade to test just clean uniform sands in centri-fuge experiments. The relative importance of the thickness of the liquefiable soil layer and its density will be explored, while examining the interacting effects of different buildings and foundation conditions on the response of the liquefiable soil and building performance. As part of this project, a focused "Student Earthquake Engineering Symposium" (SEES) that reaches out to high school students, with an emphasis on minority students, is created. The outreach program utilizes a strategy that has worked well for the sciences for the last 43 years in Northern California. Many high school students already participate in their schools' science fairs. By channeling their interests and their teachers' interests on the challenging problems involved in earthquake hazard mitigation, we can excite the next generation of earthquake engineers and scientists. As emphasized in NRC(2003), "NEES should be used to move past the prediction of free field liquefaction to the next level, which would be the ability to predict deformations ... for structures ... by considering the timing, sequence, and location of soil strength loss in the vicinity of the constructed feature." The first step towards this goal is the generation of well documented "case histories" of building response on liquefied ground, which these carefully performed centrifuge model tests will achieve. These illustrative model studies will also offer emergency managers and teachers a dramatic alternative to currently existing static pictures of tilted buildings. Video clips augmented with animated measured response data will allow the seismic hazard of liquefaction and its effect on buildings to come alive.