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民用基础设施地震工程研究的设施，并且具有世界上最大的有效载荷能力（20 MN）。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6个自由度（6DOF），由于预算限制，在2002-2004年期间由美国国家科学基金会（NSF）、地震工程模拟网络（NEES）、主要研究设备和设施建设账户作为单自由度（SDOF）系统支持建设。作为一个SDOF系统和一个多用户国家研究设施，LHPOST已经得到了NSF在NEES（2005- 2014财年）和自然灾害工程研究基础设施（NHERI）（2015财年至今）项目下的运营和维护支持。该合同将把LHPOST从目前的SDOF配置升级到完整的6DOF能力。在升级后的配置中，LHPOST将能够重现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、滚动和偏航旋转分量）。它将提供一个独一无二的设施来测试大型到全尺寸的民用基础设施，如结构、非结构、地质结构和土壤基础结构系统，在强烈地震的激励下。在水平、垂直和旋转地震输入运动的综合范围内测试基础设施的能力对于研究有效、经济和实用的新基础设施设计以及现有基础设施的地震恢复和改造策略至关重要，从而提高震后恢复能力、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数据集，以支持民用基础设施系统的高保真度、基于物理的计算模型的开发、校准和验证，从而逐步将当前对物理测试的依赖转变为基于模型的模拟，以进行此类系统的地震设计和性能评估。6DOF LHPOST提供的实验能力将支持美国在地震工程研究方面的领导地位。升级后的震动台还将提供一个独特的工具，用于教育研究生、本科生和K-12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，让他们了解自然灾害，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）。将LHPOST升级到6DOF将通过增加两个水平致动器，并将所有四个水平致动器重新配置为v形，在振动台的12.2米长，7.6米宽的平台的纵向两端，提供双轴水平运动，以及偏航运动能力。现有的6个压力平衡垂直执行器/轴承中的每一个都将配备一个高流量伺服阀，以实现垂直、俯仰和滚动运动能力。为了操作6DOF表，液压动力单元的数量将从两个增加到四个，蓄能器组的总尺寸将从9,500升增加到37,800升。在蓄能器组、水平和垂直执行器以及调压箱之间将安装一个新的管道系统。在压板底部和反应块底部之间安装第三根充氮的压紧支柱，以增加工作台的倾覆力矩能力。现有的SDOF振动台控制器（包括硬件和软件）将被具有6DOF功能的控制器所取代。还将提供一个新的液压分配系统控制器来处理安全联锁，控制液压动力单元，控制蓄能器充电和排污。此外，现有的四个安全塔的高度将增加一倍，以保护水力发电建筑免受潜在的试件倒塌。在升级期间，NHERI下的振动台将在2020年年中至2021年年中停止运行14个月。在重新开放该设施进行运营和研究之前，将对该设施进行调试，包括验收和特性测试。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.