RAPID: Large-Scale Shake Table Test to Quantify Seismic Response of Helical Piles in Dry Sand

RAPID：大规模振动台试验量化干砂中螺旋桩的地震响应

• 批准号: 1624153
• 负责人: Amy Cerato
• 金额: $ 13.32万
• 依托单位: University of Oklahoma Norman Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2019-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624153&HistoricalAwards=false
• 关键词: RAPID; Large; Scale; Shake; Table

This Rapid Response Research (RAPID) project will investigate the seismic behavior of helical piles by means of shake table tests on model piles in the UC San Diego laminar soil box. Helical piles are deep foundation elements that look like, and are installed like, a large steel soil screw - they have a slender steel shaft with any number of round plates at the tip to provide support to the structure they hold. Helical piles are spun into the ground with a large torque motor and provide support through soil bearing on the plates and along the shaft. They come in many lengths and are often the foundation of choice for retrofitting existing buildings or new, urban construction, due to their small footprint and ability to create minimal disturbance to surrounding structures. Although helical piles are installed as foundation elements in seismically active areas such as New Zealand and Japan, they have not been used widely in seismically active areas of the United States. This lack of use is, admittedly, due to having no quantifiable data to illustrate the seismic behavior of helical piles. In addition, there are no side-by-side seismic comparisons to other deep foundation systems available, other than qualitative "survival" stories like those from the 2011 Christchurch earthquake. After the series of earthquakes in 2011, the city of Christchurch was surveyed and it was found that all buildings/infrastructure constructed on helical piles sustained minimal structural damage, however, a large majority of the condemned buildings were constructed on other foundation types. The international community has qualitative proof that helical piles perform well in earthquake prone areas, but engineers have not quantified "why" those piles are superior foundation elements, and unfortunately, helical pile use in seismically active areas within the United States remains minimal. Therefore, this project seeks to find out "why" helical piles seem to behave so well in seismic regions by subjecting them to earthquake loads in the University of California - San Diego's Large Shake Table. These data are especially important and timely to generate because certain areas of the United States are now requiring seismic retrofits of existing buildings, yet engineers have a dearth of data regarding foundation systems to help make these structures safer. For example, in October 2015, the City of Los Angeles voted on a seismic ordinance that will require more than 13,000 structures, both pre-stressed concrete and soft-story wood structures, to be seismically retrofitted. Even though it is known from qualitative studies (e.g., New Zealand and Japan) that piles with comparatively small cross-section and high anchoring capacity, such as helical piles, are beneficial for seismic resistance seemingly due to their slenderness, higher damping ratios, ductility, and resistance to tip uplift, building codes and current state of practice have not been adequately developed for this pile type because no quantitative data exist. Research of seismic behavior of helical pile supported structures is therefore imperative to generate necessary data that will help ensure that helical piles are being correctly applied in seismic areas and establish quantifiable benefits and/or limitations of helical pile use in seismic areas. This project will benefit people living in seismic zones by educating engineers with full-scale helical pile experimental data so that they better understand how to design a building system that is safer, more resilient and sustainable for individuals and the community.

这项快速响应研究（快速）项目将通过对圣地亚哥UC层次堆积的模型桩进行摇桌测试来研究螺旋桩的地震行为。 螺旋桩是看起来像钢螺钉的深层粉底元素 - 它们具有细长的钢轴，并在尖端上有任何数量的圆形板，以提供对其固定结构的支撑。 螺旋桩用大型扭矩电动机旋转到地面上，并通过板上和轴上的土壤轴承提供支撑。 它们有很多长度，通常是改造现有建筑物或新的城市建设的首选基础，因为它们的占地面积很小，并且能够对周围结构产生最小的干扰。 尽管在新西兰和日本等地震活跃地区的螺旋桩被安装为基础元素，但它们尚未在美国的地震活跃地区广泛使用。诚然，由于没有可量化的数据来说明螺旋桩的地震行为，因此缺乏使用。此外，除了像2011年基督城地震那样的定性“生存”故事之外，与其他深层基础系统没有任何并排的地震比较。 在2011年的一系列地震之后，对基督城市进行了调查，发现所有建造在螺旋桩建造的建筑物/基础设施都受到最小的结构损害，但是，大部分被谴责的建筑物都是基于其他基础类型的。 国际社会有定性的证据，表明螺旋桩在易于地震的地区表现良好，但是工程师尚未量化“为什么”这些桩是卓越的基础元素，不幸的是，在美国境内的地震活跃地区使用螺旋堆积仍然很少。 因此，该项目试图通过在加利福尼亚大学（圣地亚哥的大型摇桌）中承受地震负荷，从而在地震地区找到“为什么”的螺旋桩似乎表现得很好。 这些数据尤其重要且及时生成，因为美国的某些领域现在需要对现有建筑物进行地震改造，但是工程师缺乏有关基础系统的数据，以帮助使这些结构更安全。例如，2015年10月，洛杉矶市对一项地震法令进行了投票，该法令将需要13,000多个结构，包括预压缩混凝土和软质木结构，才能进行地震改造。即使从定性研究（例如新西兰和日本）中知道，堆积的横截面和高锚定能力（例如螺旋堆）对地震抗性似乎是有益的，这似乎是由于它们的细长，较高的阻尼比，延性比，延性比，耐粘性，耐药性以及对量的量身定制的量子，并且在实践中均未开发出量的量。因此，必须研究对螺旋桩支撑结构的地震行为，必须生成必要的数据，这将有助于确保在地震区域正确应用螺旋桩，并在地震区域建立可量化的益处和/或螺旋桩使用的局限性。 该项目将通过向工程师提供全面的螺旋桩实验数据来使生活中的人们受益，以便他们更好地理解如何设计一个更安全，更具弹性和更可持续的建筑系统。