The Santa Barbara Cottage Hospital South Wing building is a 5-story 80,000 sf acute care hospital building that was constructed in 1968.  The building is a non-ductile reinforced concrete structure with a seismic force-resisting system consisting of concrete shear walls and a perimeter spandrel beam-column frame system.  The columns at the perimeter are classified as “captive” columns that are highly susceptible to shear failure is a major earthquake ground shaking event.  The foundation system consists of a combination of shallow spread footings and deep bell-caissons.

Saiful Bouquet had previously completed a seismic retrofit HAZUS project to upgrade the building to OSHPD SPC-2 status by increasing the shear strength of the captive columns and allowing it to remain in operation until 2030.  Since then OSHPD introduced the new SPC-4D structural seismic performance category that relaxed the seismic performance requirements that would allow the building to remain in operation beyond 2030 and at the same time, Cottage Hospital was projecting the need for increased acute care bed capacity.

Saiful Bouquet developed a primarily exterior seismic retrofit solution that was cost-effective and had minimal impact of the interior of the building and the functional layout and operations of the hospital.  In order to maximize the capacity of the existing structure and meet the OSHPD SPC-4d requirements, Saiful Bouquet performed an extensive performance-based nonlinear analysis of the building including soil-structure interaction and using comprehensive material testing and condition assessment results.  The seismic upgrade scheme consists of adding new ductile concrete shear walls at the exterior of the building and new steel buckling restrained braces within a concrete beam-column frame on one side of the building, which maintained clear views and daylight from the existing full-height windows.  Micropiles were used for the foundations to resist significant uplift forces and minimize the size of the foundations within the constrained site.

The project is currently in construction.