防屈曲支撑的工作机理及稳定性设计方法

Working mechanism and stability design methods of buckling-restrained braces

防屈曲支撑(BRBs)是一种兼具普通支撑和金属耗能阻尼器双重功能的新型支撑形式。虽然其概念简单明确,但是工作机理却较为复杂,而目前人们对此类支撑的本质工作机理还没有得到充分的认识,因此很难提出较为全面合理的构件稳定性设计方法。本文对防屈曲支撑的工作机理进行了剖析,比较了目前已有的构件整体稳定性设计方法并指出了其中存在的问题,进一步提出应重点考虑间隙、边界条件以及摩擦力等因素的"强度-刚度"整体稳定设计方法的观点;从理论上推导了支撑内芯屈服段与约束构件之间的局部挤压力计算公式,揭示了支撑构件局部失稳破坏的机理,并进一步提出应重点考虑内芯板件宽厚比、间隙以及局部约束条件三者相关关系的支撑构件局部稳定设计方法的观点。

Buckling-restrained braces （BRBs） are a new type of composite bracing members which can act as both conventional braces without buckling and metallic dampers. Although they are simple and clear in concept, they are complicated as for the working mechanism of such braces, so it is difficult to control their working behavior and to put forward reasonable stability design methods. This paper first probes the working mechanism of BRBs. Then comparisons are made between different overall stability design methods of which the disadvantages are pointed out and it is suggested that the effects of gap, boundary condition and friction force on the overall stability of BRB members should be taken into account on the basis of the strength and stiffness correlation theory. The theoretical formulas that determine the contact forces between the steel core and the outer restraining member are derived, which can explain the essential reason of local buckling failure of BRB members and it is also suggested that the correlation among width to thickness ratio of steel core member, gap and local restraining condition should be considered in the local stability design method.