Global buckling behaviours and design of uniform-section BRBs considering lateral load effects

Abstract

Buckling restraining braces (BRBs) have functions of both high load-carrying capacity and good energy-dissipation performance. Therefore, they are widely used in high-rise buildings and large-span space structures as lateral resistant axially-loaded members. But, in actual engineering applications, BRBs may be subjected additionally to external lateral loads so that the external restraining system (ERS) should be strengthened against the adversely lateral load effects in addition to the effects imposed by the core bending. Therefore, this paper investigates the instability mechanism and design method of BRBs considering additional symmetrical lateral load effects. First, the formula for predicting the lower limit of the restraining ratio of uniform-section BRBs is derived, based on considering the combined effect of an axial compression load of the core and a symmetrical external lateral load. Then, taking the double-tube BRB (DT-BRB) as an example, a finite element (FE) model is established with the FE software ANSYS to investigate the influence of the key parameters on the elastic buckling performance, elastic-plastic ultimate load-carrying capacity and hysteretic behavior. The FE numerical investigations of the key parameters covering the common application variation in the length and section size, the lateral load types and amplitudes, have been carried out, focusing on the effect of the parameters on the outcomes of the proposed lower limit of the restraining ratio. Finally, the design procedure for the DT-BRB is established according to the lower limit of the restraining ratio, which is used as a preliminary fundamental structural design guide in actual application.