Natural Hazards Engineering Research Infrastructure: Upgrade of the Large High Performance Outdoor Shake Table to Six Degrees of Freedom

加州大学圣地亚哥分校的大型高性能室外振动台(LHPOST)实验设施是美国同类设施中最大的，用于对民用基础设施进行地震工程研究，并拥有世界上最大的有效载荷能力(2000万牛顿)。由于没有架空高度限制，该设施可以容纳在任何振动台上测试过的最高结构。LHPOST最初设计为可容纳六个自由度(6DOF)，由于预算限制，在2002-2004年期间作为单自由度(SDOF)系统得到了国家科学基金会(NSF)、地震工程模拟网络(NEES)、重大研究设备和设施建设账户的支持。作为SDOF系统和多用户国家研究设施，LHPOST得到了NSF在NEES(2005财年至2014财年)和自然灾害工程研究基础设施(NHERI)(2015财年至今)计划下的运营和维护支持。该奖项将把LHPOST从目前的单自由度配置升级到完全的6自由度能力。在其升级后的配置中，LHPOST将能够复制地震期间地面经历的所有六个运动分量(两个水平和垂直平移分量，以及俯仰、侧滚和偏航旋转分量)。它将提供一种独一无二的设施，在强烈地震激励下测试大型到全尺寸的民用基础设施，如结构、非结构、土工结构和土-基础-结构系统。在整个水平、垂直和旋转地震输入运动组合下测试基础设施的能力，对于能够产生有效、经济和实用的新基础设施设计以及现有基础设施的抗震恢复和改造战略的研究至关重要，以提高地震后恢复能力、公共安全和国家福利的抗震性能。6DOF LHPOST将提供关键的里程碑式数据集，以支持民用基础设施系统的高保真、基于物理的计算模型的开发、校准和验证，这将逐步将目前对物理测试的依赖转移到基于模型的模拟，以用于此类系统的抗震设计和性能评估。由6自由度LHPOST提供的实验能力将支持美国在地震工程研究方面的领先地位。升级后的振动台还将提供一个独特的工具，教育研究生、本科生和K-12年级的学生，以及新闻媒体、政策制定者、基础设施所有者、保险提供商和公众，了解自然灾害以及国家需要开发有效的技术和政策来防止地震成为社会灾难。该奖项支持国家减少地震灾害计划(NEHRP)。LHPOST升级到6自由度将通过增加两个水平执行器，并在振动台长12.2米、宽7.6米的压盘的纵向两端将所有四个水平执行器重新配置为V形，以提供双向水平运动以及偏航运动能力。现有的六个压力平衡垂直执行机构/轴承中的每一个都将配备一个大流量伺服阀，以实现垂直、俯仰和滚动运动能力。为了操作6自由度工作台，液压动力装置的数量将从2个增加到4个，蓄能器组的总尺寸将从9,500升增加到37,800升。一个新的管道系统将安装在蓄能器组、水平和垂直执行器以及调压室之间。在压盘底部和反作用块底部之间将安装第三个充氮压杆，以增加工作台的倾覆力矩能力。现有的SDOF振动台控制器(硬件和软件)将被具有6自由度功能的控制器取代。还将提供新的液压分配系统控制器，以处理安全联锁、液压动力装置的控制以及蓄电池充电和排污的控制。此外，现有的四座安全塔的高度将增加一倍，以防止水力发电大楼可能出现的试件坍塌。在升级期间，NHERI下的振动台将在2020年年中至2021年年中期间停止运行14个月。在重新开放设施进行运营和研究之前，将进行设施的试运行，包括验收和特性测试。这一奖励反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The large, high-performance, outdoor shake table (LHPOST) experimental facility at the University of California, San Diego, is the largest facility of its kind in the United States for conducting earthquake engineering research on civil infrastructure, and has the world's largest payload capacity (20 MN). Because there are no overhead height restrictions, this facility can accommodate the tallest structures ever tested on any shake table. The LHPOST, originally designed to accommodate six degrees of freedom (6DOF), was supported for construction during 2002-2004 as a single degree of freedom (SDOF) system, by the National Science Foundation (NSF), Network for Earthquake Engineering Simulation (NEES), Major Research Equipment and Facilities Construction account, due to budgetary constraints. As an SDOF system and a multi-user national research facility, the LHPOST has been supported by NSF for operations and maintenance under the NEES (FY 2005-FY 2014) and the Natural Hazards Engineering Research Infrastructure (NHERI) (FY 2015 to date) programs. This award will upgrade the LHPOST from its current SDOF configuration to a full 6DOF capability. In its upgraded configuration, the LHPOST will be able to reproduce all six components of motion (two horizontal and vertical translational components, as well as pitch, roll, and yaw rotational components) experienced by the ground during earthquakes. It will provide a one-of-a-kind facility to test large to full size civil infrastructure, such as structural, nonstructural, geo-structural and soil-foundation-structural systems, under strong earthquake excitation. The ability to test infrastructure under the full range of combined horizontal, vertical, and rotational seismic input motion is critical for research that can lead to effective, economical,and practical new infrastructure designs, as well as seismic rehabilitation and retrofit strategies for existing infrastructure, to improve the seismic performance for post-earthquake resilience, public safety, and national welfare. The 6DOF LHPOST will provide critical landmark datasets to support the development, calibration, and validation of high-fidelity, physics-based computational models of civil infrastructure systems that will progressively shift the current reliance on physical testing to model-based simulation for the seismic design and performance assessment of such systems. The experimental capabilities provided by the 6DOF LHPOST will support U.S. leadership in earthquake engineering research. The upgraded shake table will also provide a unique tool to educate graduate, undergraduate, and K-12 students, as well as the news media, policy makers, infrastructure owners, insurance providers, and the public, about natural disasters and the national need to develop effective technologies and policies to prevent earthquakes from becoming societal disasters. This award supports the National Earthquake Hazards Reduction Program (NEHRP). The upgrade of the LHPOST to 6DOF will be achieved by adding two horizontal actuators and reconfiguring all four horizontal actuators into a V-shape at both longitudinal ends of the shake table's 12.2 meter long by 7.6 meter wide platen to provide bi-axial horizontal motions, as well as the yaw motion capabilities. Each of the existing six pressure balanced vertical actuators/bearings will be equipped with a high-flow servovalve to enable vertical, pitch, and roll motion capabilities. To operate the 6DOF table, the number of hydraulic power units will be increased from two to four and the total size of the accumulator banks will be increased from 9,500 to 37,800 liters. A new piping system will be installed between the accumulator banks, the horizontal and vertical actuators, and the surge tank. A third nitrogen-filled hold-down strut will be installed between the bottom of the platen and the bottom of the reaction block to increase the overturning moment capacity of the table. The existing SDOF shake table controller (both hardware and software) will be replaced by a controller with 6DOF capabilities. A new hydraulic distribution system controller will also be provided to handle the safety interlocks, control of the hydraulic power units, and control of the accumulator charging and blowdown. Additionally, the height of the existing four safety towers will be doubled to protect the hydraulic power building from potential specimen collapse. During the upgrade, operations of the shake table under NHERI will cease for a period of 14 months between mid-2020 and mid-2021. Before reopening the facility for operations and research, commissioning of the facility, including acceptance and characterization tests, will be performed.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.