梭形空间桁架约束型防屈曲支撑的性能研究

防屈曲支撑的外围约束体系的革新研究始终是其核心内容。该文提出了梭形空间桁架约束型防屈曲支撑(STC-BRB)的概念，并以BRB工程应用中的四榀桁架约束体系为例，研究了STC-BRB的静力承载力和抗震设计方法。STC-BRB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。该文建立了STC-BRB梁单元模型，采用ANSYS有限元软件对其弹性屈曲性能、弹塑性承载力和滞回性能展开研究，分别给出了基于承载力型和耗能型BRB约束比门槛值的设计方法。研究STC-BRB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，建立了承载力和抗震设计的基本计算理论和设计方法。

INVESTIGATION ON THE PERFORMANCE OF SPATIAL-TRUSS CONFINED BRBS WITH SHUTTLE SHAPE LONGITUDINALLY

Presents a Spatial-Truss-Confined Buckling-Restrained-Brace (STC-BRB) with shuttle- shape longitudinally, composed of a single steel tube core and the several shuttle-shaped trusses sharing a common external restraining tube. The strength and seismic design of an innovation research in the external restraining system of BRB has being focused on for over a few decades. The STC-BRB could significantly improve the material utilization and particularly enhance the architectural aesthetics when it is exposed externally. The elastic buckling, load resistance, and hysteretic responses of the STC-BRB are investigated numerically by adopting the finite element model (FEM) that has been validated previously by using the test results of Truss-Confined Buckling-Restrained Brace (TC-BRB). And the design method regarding the lower limit of the restraining ratios of the STC-BRBs is recommended. The elastic buckling performance of the STC-BRB is comprehensively investigated by using a beam element FE model, leading to an explicit expression of the elastic buckling load of the STC-BRB that is adopted to define the restraining ratio of the STC-BRB for its structural design. Consequently, the load resistance of STC-BRB under monotonic axial compression is numerically analyzed. Accordingly a lower limit of the restraining ratio of the STC-BRB in their monotonic axial load resistance design is recommended where the core reaches fully sectional yielding with a plasticity strain amplitude reaching 2% without global instability of the STC-BRB. The hysteretic responses of STC-BRB subjected to axially compressive-tensile cyclic loads are studied numerically, and the corresponding lower limit of the restraining ratio of STC-BRB is proposed in their energy-dissipating design. These two lower limits of the restraining ratios of the STC-BRB obtained in this study provide fundamentals for the preliminary static and seismic design of STC-BRB.