## 1 Introduction  
The lateral drifts and internal forces appear in cases where the structures are subjected to lateral forces instigated by strong ground motions or wind. The structural and non-structural members are damaged if these lateral drifts are excessive. In order to limit lateral drifts, using steel braces is one of the most well-known solutions for structures. One of the most important disadvantages in the design of the steel braces is that the tensile and the compression capacities are not equal or symmetric. [PERSON] et al. [1] reported that when the steel braces yielded under the large tension forces, they buckled under the compressive forces, and their axial load-carrying capacity suddenly decreased. This unsymmetrical hysteretic behavior in tension and compression results in a reduction in lateral stiffness and excessive damage to beams and columns in the steel braced frame. If the steel brace members are prevented from buckling, their hysteretic behavior can be shifted from unsymmetrical to symmetrical. For this reason, buckling restrained braces (BRBs) have become an attractive research topic among researchers all over the world. The BRBs consist of a core plate (CP), a casing member (CM), and debonding material (see Figure 1). The compression capacity of CP can be enhanced by using a CM or by preventingit from buckling, although it has negligible compression capacity. Therefore, the CP may yield in tension or compression or can buckle in high buckling modes. As can be seen in Figure 1, a conventional BRB has three parts, namely, an unrestrained elastic zone, a restrained elastic zone, and a restrained plastic zone. The CMs usually consist of mortar-infilled steel tubes. [PERSON] et al. [2] tested the BRBs under cyclic loading using the CMs with additional end restrainers made of steel hollow sections (SHSs) and steel plates. The debonding material was used to prevent the friction effect and stress transfer between the CP and CM. [PERSON] et al. [3] conducted tests on BRBs with CMs made of steel tubes filled with mortar and built-up steel members. BRBs with rectangular and cruciform sections were tested by [PERSON] et al. [4] and [PERSON] et al. [5]. [PERSON] et al. [6] tested BRBs with low-yield-point steel and a ductile CP. They used silicone grease to prevent friction between the CP and CM, and the compression capacity of BRBs was about 1.5 times higher than their tension capacity due to the inadequate gap between the CP and CM. [PERSON] and [PERSON] [7] used a steel pipe filled with a confined non-cohesive material. [PERSON] et al. [8] tested BRBs consisting of the I-section CP and the CM with SHS without mortar infill. [PERSON] et al. [9] suggested a way to prevent in-plane local buckling failure of a BRB whose restrainer consisted of a circular or rectangular steel tube with mortar of various thicknesses. They made a proposal that the local buckling failure of BRBs can be changed by mortar thickness and steel tube shape. An experimental program of a BRB with a CM consisting of a built-up steel section was conducted by [PERSON] and [PERSON] [10]. [PERSON] et al. [11] experimentally investigated the hysteretic behavior of BRBs that were used for retrofitting an existing structure. [PERSON] et al. [12] conducted sub-assemblage test series of the BRBs that were used to improve the lateral stiffness of a four-story steel frame. In order to determine the effects of flexure stress on the BRBs, the influence of the CP length, the axial rigidity, and fatigue life, the BRBs were tested by [PERSON] et al. [13]. BRBs with concrete-filled tubes in the steel frame were tested in  
Figure 1: Details of BRB. the USA by [PERSON] and [PERSON] and [PERSON] and [PERSON] (2014). [PERSON] et al. [PERSON] et al. (2015) and [PERSON] et al. [PERSON] et al. (2016) tested BRBs by subjecting them to both end rotation and axial displacement using a shake table facility. [PERSON] et al. [PERSON] et al. (2017) and [PERSON] et al. [PERSON] et al.