BRBM Frames: An Improved Approach to Seismic-Resistant Design Using Buckling-Restrained Braces

Buckling-restrained braces (BRBs) are an important addition to the structural engineer’s seismic design toolkit and are in widespread use in high seismic regions throughout the United States. Recently, designers and researchers have begun considering alternative bracing configurations to capture the benefits provided by BRBs in a fundamentally different way. The buckling-restrained braced mast (BRBM) frame is one such alternative configuration. The BRBM frame consists of yielding BRBs in series with a stiff elastic wide-flange mast frame that is able to pivot about its base. This mast redistributes brace forces between stories, fundamentally changing the kinematics of the system, producing a more uniform distribution of interstory drift, and eliminating the possibility of inelastic weak-story mechanisms. The BRBM system inherently provides for increased redundancy, reducing the number of frames required and providing enhanced seismic performance and better architectural compatibility at a lower cost than conventional brace-frame systems.