System Level Seismic Performance of Steel Gravity Framing

在美国的典型钢结构建筑中，设计用于抵抗侧向地震荷载的抗侧力框架只占结构系统的一小部分，而结构系统的其余部分仅设计用于抵抗重力荷载。这种重力框架通常由金属甲板地板上的混凝土组合梁组成，通过简单的剪切连接连接到建筑柱上。重力框架虽然没有明确设计用于抵抗侧向地震荷载，但可以提供显着的侧向荷载阻力，特别是由于建筑物中大量的重力框架。重力框架所提供的大变形能力和储备强度对于防止钢结构建筑在非常大的地震地面运动下倒塌具有重要作用，特别是对于那些可能没有按照目前高震区建筑施工标准建造的现有建筑。这项研究的最大影响预计将是推进现有钢结构建筑的地震安全评估程序，在评估中纳入重力系统可能会排除昂贵的抗震改造措施的需要。这种综合评价程序将使用于抗震改造的有限资源得到更有效的利用。这项研究还将为新建筑中重力系统的设计和细节提供最佳实践，这将进一步增强重力系统作为主要侧向力抵抗系统的“后备”的能力，从而提高新建筑的地震安全性。抗震建筑将通过减少建筑损坏、经济和人员损失以及伤害，促进震后国家福利、健康和繁荣。该项目的数据将在自然灾害工程研究基础设施数据库（http://www.DesigSafe-ci.org）中存档并公开提供。本研究的总体目标是通过大规模的系统级测试和稳健的数值模拟来研究重力框架系统对钢结构抗震性能和抗倒塌性能的作用。通过对大型、多隔舱、多层钢重力框架系统的测试，本研究将为钢重力体系与复合楼板系统的响应提供新的实验数据，包括考虑重力和横向框架周围隔舱的相互作用和约束。这些实验数据将有助于更好地理解钢重力框架系统的受力机制，包括连接部件、金属甲板和混凝土地板的作用。该数据以及文献中的现有数据将用于开发更现实的钢重力框架连接构件级模型，以支持钢结构建筑性能直至倒塌的地震模拟。这些新的连接模型将被传播给工程实践者和研究界，也将被用于各种原型建筑的参数化计算研究，这些建筑具有横向和重力框架设计的变化，以研究重力框架系统在减少钢结构建筑地震倒塌风险方面的作用。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。

In typical steel buildings in the United States, the lateral force resisting frames designed to resist lateral seismic loads comprise a relatively small portion of the structural system, while the remainder of the structural system is designed to resist gravity loading only. This gravity framing normally consists of composite beams with concrete on metal deck flooring, which are connected to the building columns via simple shear connections. The gravity framing, while not explicitly designed to resist lateral seismic loads, can provide significant lateral load resistance, particularly due to the large number of gravity frames in a building. The large deformation capacity and reserve strength provided by the gravity framing can play an important role in preventing collapse of steel buildings under very large earthquake ground motions, particularly for existing buildings that may not have been built to the current standards required for construction of buildings in high seismic regions. The largest impact of this research is expected to be on advancing evaluation procedures of the seismic safety of existing steel buildings, where inclusion of the gravity system in the evaluation may preclude the need for costly seismic retrofit measures. Such comprehensive evaluation procedures will allow limited resources for seismic retrofit to be used more efficiently. This research will also inform best practices for the design and detailing of the gravity system in new buildings that will further enhance the gravity system's ability to serve as a "back-up" to the primary lateral force resisting system, thereby enhancing the seismic safety of new buildings. Seismic-resistant buildings will promote post-earthquake national welfare, health and prosperity by reducing building damage, economic and human losses, and injuries. Data from this project will be archived and publicly available in the Natural Hazards Engineering Research Infrastructure Data Depot (http://www.DesigSafe-ci.org). The overall goal of this research is to investigate the role of gravity framing systems on the seismic performance and collapse resistance of steel buildings through large-scale, system-level testing and robust numerical simulations. Through testing of large-scale, multi-bay, multi-story steel gravity framing systems, this research will create new experimental data on the response of steel gravity systems with composite floor systems, including considerations of the interactions and restraint provided by surrounding bays of gravity and lateral framing. This experimental data will lead to better understanding of the force-resisting mechanisms in steel gravity framing systems, including contributions from connection components, metal decking, and concrete flooring. This data, along with existing data in the literature, will be used to develop more realistic component level models for steel gravity framing connections to support seismic simulations of steel building performance up to collapse. These new connection models, which will be disseminated to the engineering practitioner and research communities, will also be employed in parametric computational studies of a variety of archetype buildings with variations in lateral and gravity framing designs to investigate the role of gravity framing systems in reducing the seismic collapse risk of steel buildings.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.