梭形桁架约束型防屈曲支撑的破坏机理和设计理论研究

This project proposes a new type of BRBs, namely Shuttle-Shaped Truss-Confined Buckling-Restrained Brace (SSTC-BRB), and investigates its failure mechanism and design method. The SSTC-BRB is simply composed of a single steel tube core and the several shuttle-shaped trusses sharing a single external restraining tube, and would combine the characteristics of the axially loaded shuttle-shaped column and the moment-carrying truss skillfully. Therefore it can be used as the ultra-long, high load-carrying and lightweight BRB to apply to the engineering design, leading to a higher load-carrying efficiency. In association of theoretical analysis, numerical simulation and experimental investigation into the failure mechanism of SSTC-BRBs, this study focuses on the elastic buckling load, the load-carrying under monotonic axial compression and the hysteretic performance under axially cyclic loads, as well as the failure mechanism and design of the end connections. The lower restraining ratios of SSTC-BRBs under monotonic axial compression and under axially compressive-tensile cyclic loads are respectively established, particularly where the initial combined imperfections are involved in the numerical investigation. The research findings would provide guidance and fundamentals for the design and application of SSTC-BRBs in engineering practice.

本项目提出了一种新型式的梭形桁架约束型防屈曲支撑，并对其破坏失稳机理和设计理论进行研究。梭形桁架外围约束体系由主约束钢管及其周围设置的多道平面桁架所组成，其有机地把梭形受压构件和受弯桁架的受力特点相结合，具有承载效率高、设计经济的优点，可应用于超长、高承载力及轻量化防屈曲支撑的工程设计。本项目将采用理论分析、数值模拟、试验研究三者结合的研究方法，对梭形桁架约束型防屈曲支撑的失稳机理、弹性屈曲荷载、单调加载承载力、往复轴向拉压滞回性能以及节点破坏机理及构造设计进行研究，重点考虑构件整体组合初始缺陷的不利影响，确定轴向受压单调和拉压往复加载对应的约束比门槛值，建立完整的设计理论和方法。研究成果可为梭形桁架约束型防屈曲支撑的设计及应用提供依据和指导。

本项目提出了梭形桁架约束型防屈曲支撑，其由梭形桁架外围约束体系与内核钢管组成，外围梭形桁架约束体系采用外围约束钢管和多道弦杆、腹杆组成。梭形桁架约束型防屈曲支撑采用与其弯矩分布图相似的梭形桁架作为外围约束体系，具有提高材料利用率及外形美观等特点，适用于高层建筑和空间结构设置外露BRB的工程应用。.首先，给出了梭形三角桁架约束型防屈曲支撑（STC-BRB）的受力机理和设计理论。通过建立STC-BRB的梁单元模型，研究了STC-BRB的弹性屈曲性能，基于弹性屈曲荷载的理论和数值计算结果，提出了弹性屈曲荷载的计算公式，给出了BRB约束比的表达式。基于变化约束比的STC-BRB算例的计算结果，分别对其单调轴压弹塑性承载性能和拉压循环荷载作用下的弹塑性滞回耗能性能进行分析，研究了STC-BRB的失稳模式、极限承载力以及滞回耗能能力，获得了STC-BRB承载型和耗能型的约束比门槛值，建立了STC-BRB承载力和抗震设计的基本计算理论和设计方法。.其次，给出了梭形空腹桁架约束型（SSTC-BRB）的受力机理和设计理论。建立了SSTC-BRB的梁单元模型，进行弹性屈曲分析，获得了其弹性屈曲模态：单波对称失稳和双波反对称失稳，并给出了最不利初始缺陷模式。通过改变SSTC-BRB的约束比，进行弹塑性承载力分析和滞回耗能分析，获得了SSTC-BRB承载型和耗能型的约束比门槛值，建立了SSTC-BRB承载力和抗震设计的基本计算理论和设计方法。.最后，完成了4个梭形索撑型防屈曲支撑的滞回性能试验研究。试验结果表明，梭形索撑型防屈曲支撑具有良好的整体稳定性能，并并通过试验检验了端部构造设计的合理性。有限元分析与试验结果的对比验证了有限元模型的有效性和正确性，为该类防屈曲支撑的实际工程应用提供了可靠依据。