Collaborative Research: Time-Dependent Response of Reinforced Concrete Structures Near Collapse

本研究项目将研究钢筋混凝土建筑在持续重力荷载作用下的近倒塌行为。在美国，由于自然灾害以外的原因，近一半的建筑物倒塌与建筑或设计错误、老化或超载有关。这些破坏大多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破坏到整体崩溃的演变往往不是立即发生的；相反，它们是复杂的时间依赖现象，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，以便更谨慎地疏散、救援和稳定决策；受损建筑安全预估与评价并最终为设计更安全、更坚固、抗倒塌的建筑提供信息。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，立即传播研究成果，吸引代表性不足的群体，增加公众的科学参与，并对工程教育产生积极影响。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进行研究。该项目将识别和模拟对持续高应力下随时间变化的混凝土损伤敏感的结构部件的响应，检查和模拟由初始局部破坏引起的持续高应力下子结构的响应，识别系统级响应和受影响最大的部件之间的相互作用，并评估倒塌风险。在材料尺度上，本研究为持续高应力下混凝土徐变的约束效应提供了知识；在构件尺度上，研究将产生蠕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加载响应的影响；在体系尺度上，该研究将有助于理解框架和平板体系在高持续荷载作用下的性能、倒塌风险及其倒塌演化机制。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。

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.