Seismic Retrofit of Pre-Northridge Steel Moment Frame Building Using Nonlinear Static Analysis per ASCE 41-06

The need to perform cost-effective seismic rehabilitation of essential facilities has made the use of nonlinear analysis techniques an attractive option. The estimation of seismic demands on structures requires explicit consideration of the structural inelastic behavior. Therefore, nonlinear procedures such as pushover analyses are inevitably going to be more widely used. This paper presents a case study of a 10-story Pre-Northridge steel moment frame hospital building in California that was analyzed using nonlinear pushover analysis approach. Nonlinear force-deformation relationships and acceptance criteria of primary structural components were modeled in accordance to ASCE 41-06 and supplemented by experimental component testing results. Given the nature of steel moment frame buildings constructed during this era, existing connections are highly susceptible to damages during a major earthquake which could lead to an unfavorable failure mechanism. Based on nonlinear pushover analysis results, potential structural deficiencies will be identified and different rehabilitation methods will be presented. Besides, the comparisons of retrofit scopes between conventional and nonlinear methods will be highlighted. Finally and most importantly, this paper also addresses some challenges found by the authors in the implementation of nonlinear pushover analysis in seismic retrofit application, as well as recommendations from practitioner perspectives.