Seismic Retrofit of a Steel Moment Frame California Hospital Building Using Exterior Viscous Damped Frames

California legislation requires acute-care hospital buildings designed prior to the 1973 code to be evaluated, and if necessary, retrofitted to Life Safety (LS) in order to keep providing acute care until 2030. Innovative and cost-effective solutions are required in order to meet the requirements of the regulatory agency, namely the Office of Statewide Health Planning and Development (OSHPD), as well as the owner expectations. This paper presents a case study of a six-story steel moment frame structure built in 1972 that is retrofitted using supplemental viscous damping. The building is located near two major Southern California active faults. In addition, the building is triangular in plan with non-parallel lateral force resisting systems. Because of the retrofit methodology, Non-linear Dynamic Procedure (NDP) per ASCE 41-06 is required. The building will be retrofitted by adding new primary external damped 3bay moment frames and modifying the existing moment frame base connections to prevent brittle failure by allowing controlled frame uplift. The basic retrofit criterion is to upgrade to LS under an earthquake with a 10% probability of exceedence in 50 years (475 year return period), namely BSE-1 earthquake. This paper presents some of the challenges found by the authors from a constructability perspective, as well as in the implementation of the NDP for a nonconventional building geometry near two major fault lines while satisfying the acceptance criteria delineated by OSHPD and ASCE 41-06. INTRODUCTION AND BACKGROUND After the Northridge Earthquake in 1994, the California legislature enacted Senate Bill 1953 (SB 1953) with the intent of assuring the public that acute care hospital buildings would remain operational after a major seismic event. In order to address high seismic risk buildings, all hospitals were required to perform an 1620 Structures Congress 2012 © ASCE 2012