Patient Tower, St. Joseph Hospital
Tacoma, WA, USA
The 14-story patient tower is located in the greater Seattle area. It has been a celebrated concrete building ever since it was built in the early 1970’s. It was featured in the ACI Centennial Celebration in 2004 and was widely published in engineering and architectural journals.
The lateral system of the top 10-storys of the tower is composed of interior shear wall cores and curved exterior shear walls. The bottom 2-storys are the tower podium. Between the podium and level 5, all interior shear wall cores are supported by rectangular concrete columns at corners of the cores; the curved exterior concrete shear walls are supported by 16 - 36” diameter concrete columns. This created a 36 feet tall soft story, which is highly susceptible to earthquake damage.
The project structural engineers evaluated various seismic upgrade schemes. The scheme with supplemental damping offered substantial savings on the foundation work. Long bracing in the soft story prompted the use of tension-only cross bracing with Pall Friction Dampers at the intersection. Immediate occupancy performance level of FEMA-356 guidelines was achieved by providing 400 kip capacity friction dampers. Seismic retrofit was completed in 2005.