基于结构层次的防屈曲支撑内芯屈曲机理及支撑稳定设计方法研究

Buckling-restrained braces (BRBs) are a new type of composite braces which include functional benefits of both conventional braces and metallic dampers, and the stability of BRBs is the key for ensuring their damping functions. However, in BRBs’ currently used design criteria and methods, the adverse effect of seismic deformations of structure on the stability of BRBs was not considered. Thus, premature buckling failure may occur even if the design specification requirements are met. This research project focuses on the stability of BRBs in the moment-resisting frames. The analytical model is established based on system-level, and the buckling mechanism of the steel core is revealed by combining theoretical analysis and numerical simulation. Subassemblage tests proposed in design specification are used to simulate the boundary condition at the brace ends. Two sets of subassemblage tests are performed to study the effect of seismic deformations of structure on the mechanical behavior of BRBs. The system-based buckling failure mechanism and mechanic characteristic of BRBs are revealed. The numerical model is calibrated based on the test results, and parameter study is conducted to investigate the key factors on the global and local stabilities of BRBs. Combined with the results of parameter analysis, the influence of various factors on stability of BRBs is quantified, and the corresponding stability design methods are developed based on the system level. The research objectives for this project are to break though the current limitation of component-based BRB design criteria, and provide a reference for standard of seismic design. It will also offer more reliable technical and scientific basis for the safety of energy dissipation structures with BRBs in China.

防屈曲支撑是一种兼具普通支撑和金属阻尼器功能的新型支撑，而保证支撑在地震作用下的稳定是实现其耗能减震功能的关键。然而传统的稳定设计方法及现行设计标准并没有考虑地震作用下结构变形对支撑稳定性的不利影响，导致其可能提前发生失稳破坏。本项目以框架结构中防屈曲支撑为研究对象，基于结构层次建立支撑理论分析模型，通过理论分析与数值模拟相结合的方法揭示支撑内芯屈曲机理。利用规范中建议的子系统试验方法模拟实际结构中支撑的端部边界条件，通过两批子系统试验考察结构变形对支撑受力行为的影响，明确支撑失稳破坏机制及其在结构中的受力状态。根据试验结果标定数值模型，针对关键因素开展参数分析，量化结构变形等因素对支撑稳定的影响程度，基于结构层次建立防屈曲支撑整体及局部稳定设计方法。本项目有助于突破现行设计标准仍停留于构件层次的局限，为相关抗震设计标准提供参考，为我国耗能减震结构的安全性提供更可靠的技术支撑和科学依据。

防屈曲支撑目前已被广泛应用于国内外的建筑及桥梁结构中以提升其抗震性能，因此保证支撑在地震作用下的稳定是实现其耗能减震功能的关键。然而传统的稳定设计方法并没有考虑地震作用下结构变形对支撑稳定性的不利影响，导致其可能提前发生失稳破坏。本项目聚焦地震作用下钢框架结构侧向变形引起支撑节点转动对支撑受力及变形行为影响这一问题展开研究，提出基于结构层次的防屈曲支撑稳定设计方法。（1）根据支撑端部连接形式及是否考虑结构变形影响等条件，建立不同层次及不同边界条件的防屈曲支撑力学分析模型，采用稳定性二阶分析方法，揭示基于构件层次及结构层次防屈曲支撑内芯屈曲机理；（2）采用边缘纤维屈服准则，建立防屈曲支撑整体稳定设计方法，试验及有限元模拟结果表明该方法可有效保证支撑的整体稳定，以及较准确的估计支撑接触力响应；（3）基于钢管混凝土防屈曲支撑外套管抵抗局部鼓曲的需求与能力比，建立防屈曲支撑局部稳定设计方法，采用塑性设计方法，分别针对方钢管及圆钢管混凝土约束防屈曲支撑，提出了抗鼓曲承载力计算公式，通过有限元模拟及试验对提出的计算公式及设计方法完成验证。项目研究成果可为相关抗震设计标准提供参考，为我国耗能减震结构的安全性提供更可靠的技术支撑和科学依据。