全钢防屈曲支撑局部稳定性设计

LOCAL BUCKLING DESIGN OF ALL-STEEL BUCKLING RESTRAINED BRACE

外包约束构件的刚度和强度是保证防屈曲支撑(BRB)具有稳定承载力和足够延性的关键,设计时不仅要考虑整体失稳,也要考虑局部失稳。对于全钢防屈曲支撑,由于其缺乏混凝土的约束作用更容易发生局部屈曲。该文对全钢防屈曲支撑的局部稳定性进行研究。首先从理论上推导出内芯对外套管的挤压力表达式,继而针对一字形内芯全钢防屈曲支撑推导出其外套管承载力的表达式,最后将整体稳定性分析中的约束比概念拓展到局部稳定性中,得到保证全钢防屈曲支撑局部稳定的约束比表达式及其下限值。结果表明:此约束比与支撑厚度比、间厚比、内芯宽厚比、轴向应变等因素有关,在设计中应综合考虑。

The stiffness and the strength of the outer constraint component are crucial to the properties of buckling-restrained braces （BRBs）. In the design, both the local buckling and the flexural buckling should be considered. All-steel BRBs are more vulnerable to the failure in local bucking mode than those restrained by steel tubes filled with concrete, because they are not constrained by concrete. This study focuses on the local buckling of the all-steel BRBs. Firstly, the contact force between the core and the outer tube was analyzed. Then, the formula of the bearing capacity of the outer tube was deduced. Finally, the concept of constraint ratio, which was used in the flexural buckling, was introduced and used in the local buckling. The expression of the constraint ratio was obtained, and its lower limit value to prevent the all-steel BRBs from local buckling was suggested. The results indicate the constraint ratio depends on the ratio of the thickness of the tube to that of the core, the ratio of the width to the thickness of the core, the ratio of the gap to the thickness of the core, and the axial strain. All of those influencing factors should be considered in the design of the all-steel BRBs.