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Seismic Analysis and Rehabilitation of a 15 Story Pre-Northridge Steel Moment Resisting Frame Building
This paper summarizes the seismic analysis and rehabilitation design of a fifteen story steel moment resisting frame building in Oakland, California, less than five miles from the Hayward Fault. The building was constructed with connection details that were found to be vulnerable to fracture in the 1994 Northridge earthquake. Previous testing of the existing connections indicated that the welded connections were highly vulnerable to fracture, and consequently the building presented a risk to life safety in the event of a major earthquake. Seismic strengthening to meet the State of California Guidelines for the Seismic Retrofit of State Buildings Risk Level III resulted in a requirement to reduce the story drifts to 1.5% in a 475-year return period event. After considering several retrofitting schemes including connection strengthening, BRBF's and seismic isolation, a scheme that included strengthening sixty percent of the existing pre-Northridge moment frame connections and adding viscous dampers was selected. Since the existing moment connections had performed so poorly in previous testing, and because the size of the members in this building exceeded those that had been previously tested, a series of four full-scale tests were performed to confirm the validity of the connection upgrade design. Two phases of advanced analysis techniques were performed in the rehabilitation design; a study phase with multi-mode two-dimensional nonlinear pushover analyses along with single-degree-of-freedom nonlinear dynamic time-history analyses; and a working drawings phase with nonlinear response history analyses of building frames to refine the scheme and perform member checks. The extra steps taken beyond typical engineering practices were intended to provide better assurance that the project's performance goals would be met during the design basis seismic event.
Seismic Analysis and Rehabilitation of a 15 Story Pre-Northridge Steel Moment Resisting Frame Building
This paper summarizes the seismic analysis and rehabilitation design of a fifteen story steel moment resisting frame building in Oakland, California, less than five miles from the Hayward Fault. The building was constructed with connection details that were found to be vulnerable to fracture in the 1994 Northridge earthquake. Previous testing of the existing connections indicated that the welded connections were highly vulnerable to fracture, and consequently the building presented a risk to life safety in the event of a major earthquake. Seismic strengthening to meet the State of California Guidelines for the Seismic Retrofit of State Buildings Risk Level III resulted in a requirement to reduce the story drifts to 1.5% in a 475-year return period event. After considering several retrofitting schemes including connection strengthening, BRBF's and seismic isolation, a scheme that included strengthening sixty percent of the existing pre-Northridge moment frame connections and adding viscous dampers was selected. Since the existing moment connections had performed so poorly in previous testing, and because the size of the members in this building exceeded those that had been previously tested, a series of four full-scale tests were performed to confirm the validity of the connection upgrade design. Two phases of advanced analysis techniques were performed in the rehabilitation design; a study phase with multi-mode two-dimensional nonlinear pushover analyses along with single-degree-of-freedom nonlinear dynamic time-history analyses; and a working drawings phase with nonlinear response history analyses of building frames to refine the scheme and perform member checks. The extra steps taken beyond typical engineering practices were intended to provide better assurance that the project's performance goals would be met during the design basis seismic event.
Seismic Analysis and Rehabilitation of a 15 Story Pre-Northridge Steel Moment Resisting Frame Building
Graf, Timothy (author) / Malley, James O. (author) / Sinclair, Mark (author) / Newell, James (author) / Blaney, Colin (author) / Fraynt, Moisey (author) / Uang, Chia-Ming (author) / Ahmed, Tamer (author)
Structures Congress 2011 ; 2011 ; Las Vegas, Nevada, United States
Structures Congress 2011 ; 827-838
2011-04-13
Conference paper
Electronic Resource
English
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