70. SEISMIC REHABILITATION OF HISTORIC CONCRETE STRUCTURE WITH FLUID VISCO-ELASTIC DAMPERS
This paper presents the nonlinear seismic analysis, development, and implementation of an innovative seismic retrofit strategy for a six story nonductile reinforced concrete 145,000 square foot historic building. Dynamic and nonlinear static analytical results verified that the building had a weak soft story with inadequate post yield capacity and large torsional response. Hotel Stockton, in Stockton, CA, is also torsionally irregular. The analysis indicated that the existing building was not seismically adequate to withstand anticipated lateral forces generated by earthquake excitations at the site. A “collapse prevention” performance upgrade for a 475-year return event was developed. Nonlinear fluid viscous dampers were placed at the first story level to reduce the seismic demand and obtain a more uniform response. Viscoelastic fluid viscous dampers were strategically placed at one side of the building to reduce the torsional irregularity of the building. This cost effective retrofit significantly improved the seismic performance of the building.