A buckling-restrained brace (BRB) is a structural brace in a building, designed to allow the building to withstand cyclical lateral loadings, typically earthquake-induced loading. It consists of a slender steel core, a concrete casing designed to continuously support the core and prevent buckling under axial compression, and an interface region that prevents undesired interactions between the two. Braced frames that use BRBs – known as buckling-restrained braced frames, or BRBFs – have significant advantages over typical braced frames. History The concept of BRBs was developed in Japan by Nippon Steel at the end of the 1980s and was known by its trademark name of Unbonded Brace. It was first installed in the United States in 1999, in the Plant & Environmental Sciences Building in U.C. Davis. In 2002, both CoreBrace LLC and Star Seismic LLC were incorporated, and began competition with Nippon in the BRB design market. BRB usage is currently accepted, with its design regulated in current standards, throughout the world. Components Three major components of a BRB that can be distinguished are its steel core, its bond-preventing layer, and its casing. The steel core is designed to resist the full axial force developed in the bracing. Its cross-sectional area can be significantly lower than that of regular braces, since its performance is not limited by buckling. The core consists of a middle length that is designed to yield inelastically in the event of a design-level earthquake and rigid, non-yielding lengths on both ends. The increased cross-sectional area of the non-yielding section ensures that it remains elastic, and thus plasticity is concentrated in the middle part of the steel core. Such configuration provides high confidence in the prediction of the element behavior and failure. The bond-preventing layer decouples the casing from the core. This allows the steel core to resist the full axial force developed in the bracing, as designed. The casing – through its flexural rigidity – provides lateral support against the flexural buckling of the core. It is typically made of concrete-filled steel tubes. The design criterion for the casing is to provide adequate lateral restraint (i.e. rigidity) against the steel core buckling. Characteristics of buckling-restrained braces Because BRBs achieve a high level of ductility and stable, repeatable hysteresis loops, BRBs can absorb significant amount of energy during cyclic loadings, such as an earthquake event. Preventing buckling leads to similar strength and ductile behavior in compression and