Skew Adjustment Factors for Fragilities of California Box-Girder Bridges Subjected to near-Fault and Far-Field Ground Motions

Abstract

Past reconnaissance studies revealed that bridges close to active faults are more susceptible to damage, and more than 60% of the bridges in California are skewed. To assess the combined effect of near-fault (NF) ground motions and skewness, this paper evaluates the seismic vulnerability of skewed concrete box-girder bridges in California subjected to NF and far-field (FF) ground motions. The relative risk of skewness and fault-location on the bridges is evaluated by developing fragility curves of bridge components and system accounting for the material, geometric, and structural uncertainties. The skewness and a bridge site close to active faults make bridges more vulnerable, and the existing modification factor in Hazus cannot capture the variation in the median value of the fragilities appropriately. A new set of fragility adjustment factors for skewness coupled with the effect of fault location is suggested in this paper.