Collaborative Research: Time-Dependent Response of Reinforced Concrete Buildings near Collapse

本研究项目将研究钢筋混凝土建筑物在持续重力荷载作用下的濒临倒塌行为。在美国，由于自然灾害以外的其他原因导致的建筑倒塌中，近一半与施工或设计错误、损坏或超载有关。这些故障中的大多数会导致部分或全部倒塌，并发生在建筑物在持续重力载荷下的使用寿命期间。局部破坏的形成和从局部失效到全球崩溃的演变往往不是立竿见影的；相反，它们是复杂的、依赖于时间的现象，对此知之甚少。从这个项目中获得的基本知识将有助于更好地解释建筑物倒塌的早期预警信号，以便做出更谨慎的疏散、救援和稳定决策；提前预测和评估受损的建筑物安全；并最终为能够抵御倒塌的更安全、更坚固的建筑物的设计提供参考。这些结果将减少建筑失败对经济和社会的影响。该项目将与工程界合作，立即传播这项研究，吸引代表不足的群体，增加公众的科学参与，并积极影响工程教育。持续荷载对两种常见类型的钢筋混凝土建筑--弯矩框架和平板--倒塌演变的影响将通过实验模拟和数值模拟来研究。该项目将确定和模拟结构部件在持续高应力下对随时间变化的混凝土损伤的反应，检查和模拟子结构在初始局部失效引起的持续高应力下的反应，确定系统水平的响应和受影响最大的部件之间的相互作用，并评估坍塌风险。在材料尺度上，这项研究将产生关于持续高应力下混凝土徐变的约束效应的知识；在构件尺度上，该研究将产生徐变和剪切裂缝张开对柱、框架中轴向约束梁和板柱连接的持续荷载响应的影响的知识；在体系尺度上，该研究将导致对框架和平板体系在高持续载荷下的性能和倒塌风险以及倒塌演变机制的重要理解。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。

This research project will investigate the near-collapse behavior of reinforced concrete buildings under sustained gravity loads. Nearly half of the building collapses in the U.S. due to causes other than natural disasters are related to construction or design error, deterioration, or overloading. The majority of these failures result in partial or total collapse and occur during the service life of the building under sustained gravity loads. The formation of local damage and the evolution from local failure to global collapse are often not immediate; instead, they are complex time-dependent phenomena, for which little knowledge exists. The fundamental knowledge obtained from this project will facilitate better interpretation of early warning signs of building collapse for more prudent evacuation, rescue, and stabilization decisions; advance prediction and evaluation of a damaged building safety; and ultimately inform design for safer and more robust buildings able to resist collapse. These outcomes will reduce the economic and societal impact of building failure. The project will partner with the engineering community for immediate dissemination of the research, engage under-represented groups, and increase public scientific engagement, and positively impact engineering education.The impact of sustained loads on collapse evolution of two common types of reinforced concrete buildings, moment frames and flat-plates, will be studied by experimental simulations and numerical modeling. The project will identify and model the response of structural components sensitive to time-dependent concrete damage under sustained high stresses, examine and model the response of substructures under sustained high stresses caused by an initial local failure, identify system level response and the interaction among most impacted components, and evaluate collapse risk. At the material scale, the research generates knowledge for confinement effects on concrete creep at sustained high stresses; at the component scale, the research will generate knowledge of the effects of creep and shear crack opening on the sustained loading response of columns, axially restrained beams in frames, and slab-column connections; at the system scale, the research will lead to a crucial understanding the performance and collapse risk of frame and flat-plate systems under high sustained loads and the collapse evolution mechanism.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.