Retrofit of a Critical Care Facility in Los Angeles with Steel Plate Shear Walls

The 1994 Northridge Earthquake caused significant damage to steel momenet resisting frame buildings throughout the epicentral region. This damage surprised many in the seismic structural engineering community because this system was believed to provide superior ductility based on previous laboratory testing. As the damage was discovered following the earthquake, various means of seismic retrofit techniques were investigated and employed to strengthen existing buildings. The SAC Joint Venture initiative concentrated its repair research and recommendations, provided first in FEMA-273 and later FEMA-352, on methods "to restore damaged elements...to their original configuration, strength, stiffness, and deformation capacity." While these recommendations provide some marginal improvement to the original structure, they do not provide significant improvement. Therefore, an alternative to the recommendations of FEMA-273 and FEMA-352 are desirable where a higher seismic performance is necessary, such as hospital acute care buildings. Hospital acute care buildings constructed in California following the 1971 San Fernando Earthquake must be reasonably capable of providing healthcare services to the publice after a disaster. These structurres are essential facilities that provide critical post-earthquake services. The California Building Code (CBC) requires repair of structural elements where damage has reduced the lateral load capacity by more than 10% at any story. The repair must be performed in accordance with the Code at the time of repair to meet the seismic performance requirements for new hospitals. Strengthening an acute care building to restore the building to its original strength is not sufficient to meet the 2001 CBC. Therefore, a Steel Plate Shear Wall (SPSW) retrofit approach was used to stiffen and strengthen a damaged hospital building to meet these higher standards of the CBC.