结构大震变形对防屈曲支撑整体稳定性的影响及支撑设计方法

Buckling-restrained braces (BRBs), one type of promising bracing members in engineering applications, can be used as both conventional braces and metallic yielding dampers. The global stability of BRBs under severe seismic deformation condition is one of the key issues in design to ensure the function of dampers. In the currently used design methods, however, BRBs were generally idealized as one type of single bracing members and the effect of severe seismic deformations of structures on the global stability of BRBs was ignored. This research focuses on the global stability of the BRBs with bolted end connections placed in V-type bracing configuration. Subassemblage tests are used to simulate the combined axial and rotational deformations at the brace ends induced by severe seismic deformations of frame structures. Two sets of subassemblage tests are conducted to investigate the relationship between the seismic deformations of frame structures and the mechanical behavior of BRBs. The bending moment transfer mechanism between frame structures and BRBs and its effect on the BRB global stability are revealed. The design method for BRB global stability is established considering the observed deformation characteristics based on the secondary stability analysis method. Parametric study is conducted to optimize the key influential factors on BRB global stability based on the analytical results. It is expected that this research will forward the development of BRB design method from the component to the system level, and provide more reliable scientific basis and theoretical guarantee for the safety of structures with BRBs under severe earthquakes.

防屈曲支撑是兼具普通支撑与金属阻尼器双重功能的新型支撑形式，而保证支撑在大震变形情况下的整体稳定是实现阻尼器功能的关键。然而传统设计方法仅停留在独立支撑构件层次，并没有考虑结构大震变形对支撑整体稳定的负面作用。本项目以V字形支撑布置形式的两端栓接防屈曲支撑为研究对象，通过能同时施加轴向和转角变形的子系统试验方法模拟实际结构中的支撑节点边界条件，通过两批试验揭示结构变形与支撑整体受力行为的关系，阐明结构与支撑之间弯矩传递效应的产生机制，明确支撑在结构中的受力状态以及结构大震变形对支撑整体稳定的影响作用。综合考虑上述变形特征，通过稳定性二阶分析理论建立防屈曲支撑整体稳定设计方法。基于理论结果，对影响整体稳定的关键因素进行参数分析，确定设计参数的优化原则。预期成果将有助于突破国内外现行设计标准仅停留于独立支撑构件的局限，为保证耗能支撑结构在遭受超强地震时的安全性提供更可靠的科学依据和理论保障。

防屈曲支撑是兼具普通支撑与金属阻尼器双重功能的新型支撑形式，而保证支撑在大震变形情况下的整体稳定是实现阻尼器功能的关键。然而传统设计方法仅停留在独立支撑构件层次，并没有考虑结构大震变形对支撑整体稳定的负面作用。本项目围绕防屈曲支撑与结构的平面内相互作用问题，深入研究结构大震变形引起的节点转角效应对防屈曲支撑整体稳定性的影响，通过能同时施加轴向和转角变形的子系统试验方法模拟实际结构中的支撑节点边界条件，通过试验和有限元分析揭示结构变形与支撑整体受力行为的关系。研究表明，连接刚性约束会在支撑两端引入二阶弯矩效应，导致支撑提前发生平面内屈曲破坏，与传统概念假定的支撑轴向受力特征存在明显区别。以此为基础，从理论上提出考虑框架梁柱节点转角效应的防屈曲支撑整体稳定设计方法，考虑了不同支撑布置形式、布置楼层对转角变形的影响，以及支撑与节点板连接刚度的影响，最终建立了实用设计公式，能较准确地预测大变形情况下防屈曲支撑的平面内弯矩需求，便于在实际工程中对防屈曲支撑进行整体稳定设计。