## 1 Introduction  
A buckling-restrained brace (BRB) is a type of bracing component combining the functions of an ordinary brace and a metal damper [1; 2; 3; 4]. With the lateral constraint provided by the external restrainers, the steel core of BRBs can afford sufficient lateral stiffness to the main structure under a frequent earthquake and dissipate the seismic energy through their elasto-plastic deformation under a medium or severe earthquake. BRBs have been widely used in engineering applications for these advantages. Numerous studies have shown that BRBs can be used as energy dissipation fuses for the structures, in that BRBs can yield and dissipate the seismic energy prior to the main structure under seismic activity [5; 6; 7]. [PERSON] et al. [8] adopted BRBs to retrofit non-ductile reinforced concrete (RC) bridge bents. The nonlinear analysis results indicated that BRBs effectively improve the seismic performance of the existing RC bridge bents. [PERSON] et al. [9] also proposed the accurate numerical models for the BRB and SCBRB, which can reproduce hysteretic responses, including cyclic strain hardening and fatigue failure of braces. [PERSON] et al. [10] compared the relative effectiveness of different dampers by seismically retrofitting an RC double-pier bent under near-fault and far-field ground motions, in which the BRB-retrofitted bent had the higher effectiveness in reducing the bent damage under the far-field ground motions than the latter. To fully utilize the energy dissipation capacity of BRBs by retrofitting the bridge bents, a toggle BRB system, combining the functions of the structural fuse and toggle brace mechanism, was proposed by [PERSON] et al. [11]. Compared with the diagonal BRB system, the toggle BRB system exhibited a higher effectiveness of energy dissipation and a lower displacement demand. Furthermore, [PERSON] et al. [12] proposed the multistage BRBs with different yield strengths to meet the stiffness requirement of the retrofitted bend after the brace yields. The diagonal multistage BRB system had a satisfactory energy dissipation capacity, and the seismic performance of RC bents can be improved with the increasing post-yield stiffness ratio of the steel core. However, some researchers have found that the premature failure of the panel zone can be caused by the opening and closing behavior of the beam-column joint under a severe earthquake [13; 14; 15; 16]. To improve the seismic performance of buckling-restrained braced steel frames (BRBFs), [PERSON] et al. [17] proposed a beam-column-brace connection, in which the pin was introduced at the brace-gusset connection, in addition to the bolted beam splice being employed between the beam stub and beam. Thus, the negative effects of frame action can be successfully prevented. With the aim of reducing the undesired rigid gusset zone effect, two innovative beam-gusset-column connections without bending movement transferred for BRBFs were proposed by [PERSON] et al. [18], in which the gusset-to-column connection adopted slidable bolts. The finite element results verified that the BRBFs with the well-designed connections had satisfactory hysteretic responses without suffering low-cycle fatigue. As for the buckling-restrained braced reinforced concrete structures, the corresponding panel zone has the more complex configuration and working mechanism. Figure 1 demonstrates three traditional gusset-to-frame connection configurations. Obviously, the first two connections cannot reduce the frame action effect due to their rigid connections. In spite of the opening and closing behavior of the gusset connection being diminished using the third method, the additional strong shear interaction at the beam end might induce the premature shear failure of the concrete beam or buckling failure of the BRB. Large-scale self-centering buckling-restrained braced reinforced concrete double-column bridge piers with an anchorage plate connection was experimentally and numerically investigated by [PERSON] et al. [19; 20].