Seismic Retrofit of a 1960's Steel-Frame Industrial Building In Washington State Using Viscous Dampers

摘要

Viscous dampers were implemented in the seismic retrofit design of a building in a large industrial facility near Seattle, Washington. The retrofit of this late-1960's building was designed to meet the ASCE 41-06 Standard for the Seismic Rehabilitation of Existing Buildings' Basic Safety Objective (BSO), which consists of the dual performance goals of life safety in the BSE-1 event (seismic hazard with 10% probability of exceedence in 50 years) and collapse prevention in the BSE-2 event (seismic hazard with 2% probability of exceedence in 50 years). The four-story, 112' tall steel-framed building consists of three levels of nonductile concentrically braced frames above a thirty-seven foot tall unbraced (soft) story. Due to the manufacturing processes contained within the building, the retrofit design reduces but doesn't eliminate its soft-story configuration; viscous dampers will be located within the bottom story to reduce lateral displacement demands and minimize required foundation work. In addition to the installation of dampers and limited foundation work, connection strengthening was required within the braced frames and the roof trusses to meet the selected performance objective. Parametric studies verified superior performance of viscous dampers relative to that of similarly sized friction dampers. Building performance was validated through a non-linear response history analysis. The building site is located approximately 100 kilometers from the Cascadia Subduction Zone (9.0 Mw) and less than one kilometer from a 7.44 Mw crustal source. Probabilistic seismic hazard analysis confirmed the significant contribution from each source and a total of ten earthquake records were selected and scaled to capture the range of seismic ground motions expected at the site. Vertical acceleration components were included for each record to predict the response of the long-span roof trusses.