Seismic Upgrade in San Francisco Using Energy Dissipation Devices

Abstract

For the first time in the United States, earthquake energy dissipation devices have been used for the seismic upgrade of a building located in San Francisco, California. The devices used are Added Damping and Stiffness (ADAS) elements which consist of 50 ksi steel plates which deform plastically during severe earthquakes to dissipate energy. The ADAS elements were used in conjunction with steel chevron braces as part of the seismic upgrade of a 2-story nonductile concrete frame structure built in 1967. The building suffered both structural and nonstructural damage during the 1989 Loma Prieta Earthquake and appeared to be a life safety hazard for a major earthquake. The ADAS upgrade scheme was selected over other more conventional schemes, in part, because the design seismic force could be limited to the capacity of the existing foundation system. The paper provides a case study and summarizes the seismic evaluation and upgrade design, the linear and nonlinear analyses performed, modeling assumptions, unique design details, the permit approval process, and final construction. In addition, comparisons are presented showing shear forces and displacements for the original building and the final design with chevron braces and ADAS elements.