Rockridge Geotechnical (RG) performed a geotechnical investigation and provided geotechnical services during the renovation of the Graduate Hotel at 488 University Avenue in Palo Alto. The investigation included site-specific ground motion hazard analysis and the development of scaled earthquake time series for selected hazard levels for non-linear dynamic structural analysis.

Previously, the hotel had been converted into an apartment complex before various renovations turned the building back into a hotel. The restoration of the hotel included significant structural and life-safety upgrades, including seismically retrofitting the building. The reinforced-concrete and timber-framed structure was constructed in 1929, and it includes one basement level. Previous seismic strengthening was completed in 2003.

The primary geotechnical issue associated with the seismic strengthening of the development is providing adequate foundation support for the strengthening elements. The seismic strengthening scheme included a new lateral line of resistance in the middle of the building, two new steel buckling restrained braced frames, a new shotcrete overlay, and foundation improvements at the locations of basement shear walls where existing foundations are inadequate. RG provided recommendations for an analysis of the existing spread footings and the installation of new spread footings. RG recommended the installation of a new deep foundation that consisted of micropiles where additional uplift resistance was needed.

RG also provided geotechnical observation services during the hotel’s restoration. These services included observing the preparation of the site, as well as observing the conduction of a proof-test program to confirm micropile bond lengths.