Efficient seismic fragility assessment of highway bridges on liquefiable soils
Master of Science
The increasing failure potential of U.S. highway bridges from aging and susceptibility to damage in extreme events, such as earthquakes, necessitates the development of efficient assessment tools to help infrastructure owners prioritize maintenance and rehabilitation interventions. Particularly, seismic fragility curves are useful tools because they state the failure probability of structures conditioned on earthquake intensity levels. This study focuses on computationally efficient coupled bridge-soil-foundation (CBSF) analyses and develops fragility curves for multi-span continuous steel bridges (MSCS) typical of the central and eastern U.S. (CEUS) when exposed to earthquake-induced soil liquefaction. The resulting fragility curves show an increase in the vulnerability of rocker bearings and bent piles. Moreover, depending on the type of soil layer overlying the liquefiable sand, liquefaction either decreases or increases the fragility of columns, whereas the probability of unseating at the abutments increases when liquefaction is explicitly modeled. Lastly, bridge system fragilities are increased for extensive and complete damage.