Seismic fragility assessment of steel frames for consequence-based engineering: A case study for Memphis, TN

Consequence-Based Engineering (CBE) is a risk management system that is aimed at providing insight into the seismic performance of civil infrastructure including buildings, bridges and transportation and utility systems. The performance assessment of civil engineering structures and systems subjected to earthquakes must account for the substantial uncertainties in the seismic demands and the nonlinear behavioral characteristics and capacities of complex engineered facilities. A key aspect of this performance assessment is fragility modeling of building structures. This paper describes an approach to the building fragility assessment component of CBE, and illustrates this approach for steel frames typical of regions of low-to-moderate seismicity in the Central and Eastern United States. We begin with a description of seismic risk assessment for civil infrastructure to show where the building fragility modeling process fits into the CBE decision framework. We then consider three steel frames of different heights, designed by different building codes: the first two are moment frames with fully restrained and partially restrained connections and the third is a braced frame. Seismic fragilities for these frames are determined from assessment of their responses to ensembles of synthetic ground motions generated for the Central and Eastern US, probabilities of four distinct performance states are determined, and implications for seismic risk assessment are discussed.