Seismic Retrofit of the Marin County Hall of Justice Using Steel Buckling-Restrained Braced Frames

摘要

The Steel Buckling-Restrained Braced Frame (BRBF) is a new element in the Structural Engineer's toolkit. It provides the familiar stiffness and strength of a steel brace, without the problem of compression buckling. In addition, yielding limits the maximum force in connections and collecting elements, simplifying design. Lastly, the Steel Buckling-Restrained Braced Frame can also be used to dissipate energy through stable hysteretic behavior. Steel Buckling-Restrained Braced Frames were chosen for the retrofit of the Marin County Hall of Justice, originally designed by Frank Lloyd Wright. The investigation showed many lateral structural deficiencies including non-continuous columns, inadequate number of lateral resisting elements, inadequate diaphragm strength, inadequate transfer mechanisms between resisting elements, and incompatible building segments. Steel Buckling-Restrained Braced Frame elements were chosen as part of the retrofit scheme for their ability to limit the load on the weak diaphragm, to reduce the interstory drift of the building during a seismic event, as well as their ability to dissipate energy during high level earthquakes. The seismic retrofit scheme was constrained by the architecturally sensitive public spaces and maintaining the building's functionality throughout construction.