NEESR: Seismic Resilience of Pre-Tensioned Bridge Bents

本研究旨在探索一套同时实现桥梁排架设计和施工三大进步的系统：改进的抗震性能、更快的现场施工速度和更好的长期耐久性。首先，将通过使用无粘结先张力柱来解决抗震性能问题，目标是在地震后将桥梁重新居中。其次，更快的现场施工是通过使用预制来实现的，这种预制通常与预张拉齐头并进。连接细节很关键，但已经开发了基本配置。第三，在关键区域使用高性能材料(混杂纤维增强混凝土(HyFRC)、不锈钢棒和环氧涂层绞线)来解决长期耐久性问题。已经进行了试点研究，并表明该系统具有所需的基本特征，并有可能产生预期的效益。然而，需要对系统的关键方面进行研究，并且需要开发数值模型来研究其在各种条件下的动态性能。这项研究是华盛顿大学、加州大学伯克利分校和内华达大学雷诺分校的合作成果。用这一新系统设计的两跨桥梁的测试将使用小乔治·E·布朗。位于里诺内华达大学的地震工程模拟网络(NEES)振动台设施。该项目的数据将被存档，并通过http://www.nees.org.This的NEES项目仓库数据库向公众提供。该项目旨在通过同时改进地震区桥梁的设计和建造方式，打破长期存在的三个“更好、更快、更便宜”模式中的两个模式的限制。更好的方面是建立在基本技术的基础上，这些技术已经被证明适用于建筑，并被用于抵御旧金山一座40层混凝土建筑的地震荷载等。先张法正在适应桥梁的使用，通过在关键区域战略性地采用高性能材料进行补充和优化，例如不锈钢和纤维混凝土，这两种材料都是因其韧性而被选择的。这些材料将确保桥梁在地震发生后立即重新对准并向包括应急车辆在内的交通工具开放，并提供比传统材料更好的长期耐久性，从而极大地提高了对地震运动的反应能力。通过使用精心设计的预制，可以实现更快的速度，这意味着许多组件可以在现场制造并在现场快速连接在一起。这些连接必须易于组装，但具有很高的抗震能力。同时实现这两个目标是具有挑战性的，但由于该系统的创新配置，这是可能的。随着施工时间的显著缩短，预计会出现“更便宜”的情况。对该系统各个方面的初步研究已经证明了它们的可行性。这项研究着眼于整个系统，优化其部件的布置和细节，并建立工程师在实践中设计所需的数学模型，以降低国家老化的桥梁基础设施的重建成本。该奖项是国家减少地震灾害计划(NEHRP)的一部分。

This research investigates a system to simultaneously achieve three major advances in the design and construction of bridge bents: improved seismic performance, faster on-site construction, and better long-term durability. First, the seismic performance will be addressed through the use of unbonded pre-tensioned columns, with the goal of re-centering the bridge after an earthquake. Second, the faster on-site construction is to be achieved through the use of pre-fabrication, which typically goes hand-in-hand with pre-tensioning. Connection details are critical, but basic configurations for them have already been developed. Third, the long-term durability is to be addressed by the use of high performance materials (hybrid fiber-reinforced concrete (HyFRC), stainless steel bars, and epoxy-coated strands) in key areas. Pilot studies have already been conducted and have shown that the system possesses the desired fundamental characteristics and has the potential to deliver the anticipated benefits. However, key aspects of the system need to be investigated, and numerical models need to be developed to investigate its dynamic performance under a wide variety of conditions. This research is a collaboration among the University of Washington, University of California at Berkeley, and University of Nevada, Reno. The testing of a two-span bridge designed with this new system will be conducted using the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) shake table facility at the University of Nevada, Reno. Data from this project will be archived and made available to the public through the NEES Project Warehouse data repository at http://www.nees.org.This project aims to break the limitation of achieving two out of the three long-standing "better, faster, cheaper" paradigm by providing three simultaneous improvements to the way that bridges are designed and built in seismic areas. The "better" aspect is provided by building upon basic technology that has been proven for buildings and was used to resist the seismic loads in a 40-story concrete building in San Francisco, among others. Pre-tensioning is being adapted for use in bridges, where it is being supplemented and optimized by the strategic inclusion in key regions of high performance materials, such as stainless steel and fiber-reinforced concrete, which are both selected for their toughness. Those materials will provide a quantum improvement in the response to earthquake motions by ensuring that bridges re-align properly and are open to traffic, including emergency response vehicles, immediately after an earthquake, and also by providing better long-term durability than is possible with conventional materials. The "faster" is achieved by the use of carefully designed pre-fabrication, which means that many components can be made off site and connected together rapidly on site. The connections must be easy to assemble but highly resistant to earthquake forces. Achieving those two goals together is challenging, but is possible due to the innovative configuration of the system. The "cheaper" is expected to follow from the significant reduction in construction time. Preliminary studies on individual aspects of the system have already shown their viability. This study focuses on the whole system, to optimize the arrangement and details of its components, and to create the mathematical models needed by engineers to design it in practice to reduce the cost of rebuilding the nation's aging bridge infrastructure. This award is part of the National Earthquake Hazards Reduction Program (NEHRP).