# Development of a New Rubber Buckling-Restrained Brace System for Structures
## 2 Development of Rubber Buckling-Restrained Brace (RBRB)  
The Buckling-Restrained Brace (BRB) system relies on the performance of its core under both compression and tension. Consequently, the steel core is crucial for the load-bearing capacity and overall effectiveness of the device. This study aims to enhance the vibration dissipation capacity and increase energy absorption during severe seismic events. This is achieved by incorporating specially designed hyper-elastic rubber as a key component in the load-bearing mechanism. For this purpose, experimental tests were conducted on both conventional BRBs and the proposed RBRB. The performance of both devices was then compared using finite element simulation to evaluate the impact of the bracing systems on building behavior through the performance-based design (PBD) method. Given the identified limitations of conventional BRBs, it was determined that a high-performance, lightweight BRB system is needed. Such a system should not rely heavily on core element manipulation or extensive calculations to enhance performance and mitigate existing issues. The incorporation of rubber in the BRB design is due to its high bulk modulus of elasticity (K) and low shear modulus (G). Rubber's high resistance to volume change under load ensures sufficient load-bearing capacity due to its high stiffness characteristics. As an incompressible material, rubber has a Poisson's ratio of exactly 0.5. For applications where rubber is not highly confined, assuming incompressibility is reasonable and is a critical component of many mathematical models developed for rubber [77; 78; 79]. Rubber in RBRB enhances the vibration dissipation capacity and absorbed energy of the system. In the fabrication process of conventional BRBs, the core components are divided into two sections: 40% for the plastic section and 60% for the elastic section [80]. Next, the core is placed inside a hollow steel tube restrainer, which serves to confine the device. After this step, concrete is cast inside the hollow steel section, surrounding the core while maintaining a gap to allow for local buckling of the core element. The procedure of fabricating the RBRB is shown in Figure 1a. It consists of elastic and plastic sections (1). Section one is the core of the system and consists of the steel plate, which is assumed to have plastic behavior, and two steel hollow sections as the elastic parts, which should have more resistance and remain elastically during loading. The elastic part has been chosen as the hollow section, which is welded to the steel support head plates to have more resistance against forces. Figure 1: (**a**) Procedure of fabrication of the RBRB. (**b**) Proposed RBRB after assembling. (**a**) Assembly steps. (**b**) Proposed RBRB. The steel core was assembled by connecting the plastic and elastic sections (1), then dividers (1) (which are steel plates) were placed through the core between the elastic and plastic sections (1). By finalizing the steel core (2), it was inserted inside the steel tube restrainer. Then, the concrete (5) was casted inside the steel tube restrainer by considering the gap for rubber cubes (3,4). Further, the rubber components were fitted carefully in the considered gap between the steel divider and concrete (6). The difference between the rubber shapes is due to the main core dimensions. Since it has a steel plate as the main core (plastic part) and two hollow sections (as elastic parts) on both sides, one set of rubber components has the dimension of the main core (plastic part), and the other set is based on the steel hollow section core (elastic part). The steel hollow section (7) has the role of restraining the whole device. Steel caps (7) were added to both ends of the steel tube restrainer to take the imposed transferred force and not pull out the core during testing. In the last step, steel support heads (8) were situated at both ends of the device to fix the device to the actuator head and support.