大震作用下防屈曲支撑附加力对支撑跨RC框架梁柱破坏模式的影响机理

Buckling-restrained braces (BRBs) are widely used to enhance seismic behaviors of RC framed structures. However, the adverse effect of interaction induced by BRBs on seismic behavior of RC frame in the braced bay under severe earthquake is not reasonably taken into account in the current structural design. Thus, damage maybe occur for beams and columns prior to BRBs, leading to lose the energy dissipative capacity of BRBs. Moreover, failure mechanisms of RC frame beams and columns have not been revealed in structural strengthening or improvement methods presented by previous studies. A research approach from beam-column subassemblage level to framed structure level is proposed by this research to investigate the effect of secondary forces induced by BRBs. Firstly, experimental study, analytical simulation and theoretical analysis at beam-column subassemblage level are conducted to investigate the effect of secondary forces induced by BRBs on the mechanical states of RC frame beams and columns in the braced bay under severe earthquake. The shear and shear-flexural failure mechanisms of structural members in the braced bay are revealed. Then, analytical simulation and theoretical analysis at framed structure level are conducted to investigate the effect of secondary forces induced by BRBs on the deformation capacity of RC frame in the braced bay. The flexural failure mechanism of structural members in the braced bay is revealed. Finally, a practical design method for the braced RC frame is proposed, taking into account the adverse effect of above secondary forces. It is expected that this research will improve energy dissipation capacity of BRBs on the braced RC frame and provide more reliable scientific basis and theoretical guarantee for the safety of energy dissipation structural system in severe earthquake-prone regions in China.

防屈曲支撑被越来越多地应用在我国RC框架结构中以提高其抗震性能。然而目前RC框架设计中并未合理地考虑大震作用下支撑对结构的作用对支撑跨框架抗震性能的不利影响，导致其梁柱可能先于支撑发生破坏，从而丧失支撑的耗能减震效果。并且学者提出的结构加固或改进方法未揭示框架梁柱破坏机理。本项目拟采用从“梁柱组合件”层次到“框架结构”层次考察支撑附加力影响的技术路线。通过梁柱组合件试验研究、数值模拟和理论分析来明确大震作用下支撑附加力对支撑跨框架梁柱受力状态的影响程度，揭示梁柱剪切破坏和弯剪破坏机理。通过框架结构数值模拟和理论分析来明确大震作用下支撑附加力对支撑跨框架结构变形能力的影响程度，揭示梁柱弯曲破坏机理。综合考虑上述支撑附加力影响，建立一种结构实用设计方法。预期研究成果有助于充分发挥防屈曲支撑对RC框架结构的耗能减震效果，为我国高烈度区耗能减震结构安全性提供更可靠的科学依据和理论保障。

课题针对目前大震作用下防屈曲支撑RC框架的子框架梁柱设计未合理地考虑防屈曲支撑附加力的不利影响，导致子框架梁柱可能先于防屈曲支撑发生破坏的难点问题，深入研究了大震作用下防屈曲支撑附加力对RC子框架梁柱受力状态和破坏模式的影响规律，并提出了相应的子框架梁柱设计方法。子框架梁柱受力状态方面，开展了7个足尺防屈曲支撑RC梁柱组合件破坏模式拟静力试验研究，考察了节点板与梁柱连接形式、梁D区抗剪设计、附加塑性铰外移纵筋等研究参数的影响，节点板与梁柱连接形式对子框架梁柱受力状态影响较大，牛腿设计方法能够保证梁D区具备足够的抗剪承载力，塑性铰外移可以改善D区受力状态；明确了大震作用下防屈曲支撑附加力影响下RC子框架梁柱的受力状态和破坏模式，明晰了防屈曲支撑附加力对RC梁柱塑性铰转移、梁柱D区受力性能以及梁柱延性的影响规律。子框架梁柱破坏机理方面，对防屈曲支撑附加力影响下RC子框架梁柱受力状态和破坏模式进行数值模拟以及理论分析，考察了支撑轴力、节点板与梁柱连接形式、梁柱剪跨比、梁柱配筋构造等研究参数，界定了子框架梁柱塑性铰转移的临界条件，节点板与梁柱之间的切向约束程度对塑性铰转移影响较大；明确了防屈曲支撑附加力对RC子框架梁柱受力状态和破坏模式的影响程度，揭示了RC子框架梁柱的剪切破坏和弯剪破坏机理，牛腿设计方法和塑性铰外移能够有效地避免梁D区发生剪切破坏和弯剪破坏。在上述研究结果基础上，建立了考虑大震作用下防屈曲支撑附加力影响的子框架梁柱设计方法。本项目研究成果有助于更合理地预测和保证RC子框架大震性能，为我国高烈度区耗能减震结构安全性提供更可靠的科学依据和理论保障。