Tribune Tower Voluntary Seismic Retrofit

The iconic Tribune Tower in Oakland was erected in 1906 and is registered with the National Register of Historic Places. The steel 19-story office building structure is over two basement levels with a lower basement level finished floor about 21½ feet below sidewalk grades. In 2017-2018, a seismic evaluation and voluntary seismic retrofit was performed on the structure. The retrofit also involved strengthening the adjacent Breuner Building, which is a 6-story concrete building over one basement level. The intent of this retrofit is to lower the Probable Maximum Loss (PML) to below 20 percent for the two buildings. As the geotechnical engineer of record, Langan performed an investigation of the soil conditions and reported our findings and recommendations, including detailed recommendations for a performance based design approach for the retrofit. We also performed a site-specific seismic hazard analysis to develop site-specific horizontal response spectra and earthquake time series. Because of the close proximity of the site to the Hayward fault, we developed response spectra and associated time series in the fault normal and fault parallel directions.
2018 ASCE San Francisco Section Awards: Outstanding Seismic Retrofit