U.S. GSA James R. Browning Courthouse Seismic Evaluation
San Francisco, California, USA
Slate performed geotechnical/geohazards evaluations and provided recommendations for the seismic retrofit of the James R. Browning U.S. Courthouse in San Francisco, headquarters for the U.S. Court of Appeals for the Ninth Circuit. The building, which opened in 1905, survived the 1906 San Francisco Earthquake, but was damaged during the 1989 Loma Prieta earthquake and subsequently retrofitted with a friction pendulum base isolation system. The building is listed on the National Register of Historic Places.
- Developed code-based and site-specific horizontal and vertical response spectra, following the guidelines of ASCE/SEI 7-16 and ASCE/SEI 41-17, including BSE-2N, BSE-1N, BSE-2E and BSE-1E.
- Developed probabilistic response spectra for the 2,475-, 975-, 475 and 225-year return periods.
- Developed two suites of 11 sets of scaled acceleration time histories (with each set containing two orthogonal horizontal components and one vertical component). Selection of time history records will be based on a deaggregation of the ground motion hazard values and known subsurface conditions at the site.
- Developed an estimate of the return period of the seismic hazard associated with the contact between the building and the moat wall based on parameters provided by clients.
- Assessed geohazards at the site, such as surface fault rupture, soil liquefaction; differential compaction (settlement), landslides and flooding in accordance with ASCE/SEI 41-17 and the ASCE/SEI 41-17 “Geologic Site Hazard and Foundation Checklist”.
- Provided recommendations for mitigation measures for each seismic-related geotechnical hazard identified in the evaluation phase. Provided commentary on mitigation efforts and the expected impact to the building from the seismic-related geologic hazard.
- Developed recommendations regarding ultimate values for soil bearing, coefficient of friction, subgrade modulus, and passive pressure for spread footings, as well as pile capacity estimates and retaining wall design pressures.