SEAONC Dinner Meeting
Research and Implementation of the
Buckling Restrained Braced Mast System
Leo Panian, SE, Principal, Tipping Structural Engineers
Barbara Simpson, Ph.D. Candidate, UC Berkeley, SEMM
Tuesday, February 2, 2016, City Club, San Francisco
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.
Results from a full-scale mast experimental test done by UC Berkeley show that this system can be effective in limiting a soft or weak story mechanism, and preliminary numerical results have shown that it may also yield better performance than conventional braced frames. 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.
Leo Panian practices from the intersection of seismic engineering, advanced analytics, and new technology to deliver effective, cost-efficient, and high-performance projects for his clients. Holding an MS in structural engineering from UC Berkeley and a BS in structural engineering from UC San Diego, Leo joined Tipping in 1997 and was named principal in 2011. Leo has led and managed many of Tipping’s ambitious projects, including the SF Public Utilities Commission Headquarters (SFPUC), UC Berkeley’s Campbell Hall; he currently leads Tipping's structural engineering team for San Francisco’s Moscone Center expansion. Several of his projects have garnered regional and national recognition for innovation and engineering excellence, including the SFPUC, Berkeley’s 2850 Telegraph Avenue, and the historic Pacific Place and Landmark at One Market Street in San Francisco.
Barbara Simpson is presently a doctoral candidate at UC Berkeley. She received her Bachelor of Science from the University of Kansas and Master of Science from UC Berkeley. Prior to beginning her graduate studies, she worked for nearly a year at Thornton Tomasetti in both the Kansas City and Los Angeles design offices. Her research with Professor Steve Mahin, Principal Investigator of the BRBM system, focuses on the performance and retrofit of existing steel braced frames, funded by an NSF research grant. As a part of this research, she has designed, built, and tested three nearly full-scale steel braced frames, including one strongback, or "mast", retrofit designed to improve braced frame performance.
San Francisco, CA 94104
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