NEESR-CR: Design of Soil and Structure Compatible Yielding to Improve System Performance

该奖项由2009年美国复苏和再投资法案(公法111-5)资助。该奖项是NSF 09-524项目征集“小乔治·E·布朗地震工程模拟(NEES)研究网络(NEESR)”竞赛的结果，包括加州大学戴维斯分校(牵头机构)和圣克拉拉大学(分奖机构)，以及加州大学圣地亚哥分校(分奖)。该项目将利用加州大学戴维斯分校的NEES设备现场。当一场大地震撼动一个大都市地区时，数十亿美元和数千人的生命处于危险之中。建筑物损坏或倒塌是造成风险的主要因素之一。为了改善新旧结构的性能，正在进行巨额投资，包括结构或机械能量耗散装置，如阻尼器(巨型减震器)，甚至是复杂的计算机控制的执行器，以抵消地震震动的影响。然而，岩土和结构工程师普遍认为，只要让地基吸收能量，就可以有效地消散大量破坏性的震动能量。本来会损坏建筑物的能量可以通过土壤-地基界面的摩擦和辐射回到地面而消散。土木工程师今天明白这一点，但他们不愿设计基础坚固(只有一点点)的建筑，原因是：(I)可以理解的看法，即岩土材料属性比结构材料属性更不确定，以及(Ii)在我们传统的工程设计过程中，结构和岩土责任之间的分割。(目前，结构工程师设计建筑物的地面部分，岩土工程师设计基础，两者之间的相互作用很小。)尽管很明显，浅基础的承载能力对不确定的土性非常敏感，但典型的浅基础的弯矩能力比承载能力更可预测。摇摆还有一个额外的好处，那就是引入了一种自然的自我中心倾向；想象一下，把冰箱倾斜几度，然后松开？冰箱会来回摇晃，但它最终会垂直站立(这就是我们所说的？自我中心？)。例如，岩土工程师和结构工程师需要共同努力，以确保基础的摇摆运动与建筑物其他部分的运动相一致。这项工作将把来自大学和私人工程公司的结构和岩土工程领域的领导者聚集在一起，研究如何进行协作式整体建筑设计，使我们能够设计可以在摇动基础上移动的建筑，从而使我们能够利用基础中具有成本效益的能量消耗。包括执业工程师在内的一个强大的技术转移团队将与该项目的学者合作，以帮助确保创新概念不会不切实际。与积极参与建筑规范修订的建筑工程师和执业工程师合作，也将有助于加快我们的成果被专业人士采用。避免过度设计、过于保守的基础，并减少对上部结构内耗能机制的要求，将节省建筑成本，并可以提高性能。几乎没有可用的实验数据来表明摇动的基础将如何与屈服的结构系统动态地相互作用。这项提议将通过在NEES离心机设施上进行实验来填补这一空白。经过实验验证的计算机模拟将被用来在更大范围的原型情况下推广发现。虽然我们的工作主要集中在建筑物上，但将耗能和自中心结合在一起的非弹性地基行为适用于大量的桥梁、塔楼和更高的建筑。性能的改善将导致减少与地震相关的经济和人员损失。通过邀请MESA(一个帮助教育困难学生在数学、工程和科学方面取得成功的组织)的学生团体在当地社区大学学习土木工程来招募新工程师的努力将有助于培养多样化的工程劳动力。该项目的数据将被存档，并通过NEES数据库向公众提供。

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 and includes the University of California, Davis (lead institution) and Santa Clara University (subaward), and the University of California, San Diego (subaward). This project will utilize the NEES equipment site at the University of California, Davis.Hundreds of billions of dollars and thousands of lives are at risk when a major earthquake shakes a metropolitan area. Building damage or collapse is one of the primary contributors to the risk. Huge investments are being made to improve performance of new and old structures by including structural or mechanical energy dissipation devices such as dampers (huge shock absorbers) and even complex computer controlled actuators to counteract effects of earthquake shaking. Geotechnical and structural engineers, however, generally understand that a lot of the damaging shaking energy can be effectively dissipated just by allowing the foundations to absorb the energy. Energy that would otherwise damage a building can be dissipated through friction at the soil-foundation interface as well as by radiation back into the ground. Civil engineers understand this today, but they are reluctant to design buildings with foundations that rock (just a little) due to: (i) the understandable perception that geotechnical material properties are less certain than structural material properties and (ii) the partition between structural and geotechnical responsibility in our traditional engineering design process. (Presently, structural engineers design the part of the building above the ground and geotechnical engineers design the foundations, and there is minimal interaction between the two.)While it is clear that the bearing capacity of shallow foundations is very sensitive to uncertain soil properties, the moment capacity of typical shallow foundations is much more predictable than the bearing capacity. Rocking has the added benefit of introducing a natural self-centering tendency; imagine tilting a refrigerator a few degrees, and then letting go ? the refrigerator will rock back and forth a little, but it will eventually end up standing vertical (this is what we mean by ?self-centering?. Geotechnical and structural engineers would need to work together to ensure that rocking movement of a foundation, for example, is compatible with the movement of the rest of the building. This work will bring together leaders in structural and geotechnical engineering from universities and private engineering firms to figure out how to perform the collaborative holistic building design that allows us to design buildings that can move with a rocking foundation and hence allow us to take advantage of cost effective energy dissipation in the foundation. A strong technology transfer team that includes practicing engineers will work with the academics in this project to help ensure that innovative concepts are not impractical. Teaming with construction and practicing engineers actively involved in building code revision will also help speed our results toward adoption by the profession.Avoiding over-designed, over-conservative footings and reducing requirements for energy dissipation mechanisms within the superstructure will save construction costs and can improve performance. There is almost no experimental data available to indicate how rocking foundations will dynamically interact with a yielding structural system. This proposal will fill this gap by performing experiments on a NEES centrifuge facility. Computer simulations validated by experiments will be used to generalize findings over a larger range of prototype situations. Although our work focuses on buildings, the use of inelastic soil-foundation behavior incorporating energy dissipating and self-centering is applicable to a large array of bridges, towers, and taller buildings. Improved performance will lead to a reduction in economic and human losses associated with earthquakes. An effort to recruit new engineers by inviting groups of students in MESA (an organization that helps educationally disadvantaged students succeed in Math, Engineering, and Science) programs at local community colleges learn about civil engineering will help grow a diverse engineering workforce. Data from this project will be archived and made available to the public through the NEES data repository.