Post-earthquake Assessment of Mission-Gothic Undercrossing

Collapse behavior of Mission-Gothic Undercrossing under Northridge earthquake is studied by performing nonlinear time-history analysis and three-dimensional nonlinear finite element method for flared columns. Bridge structural model is characterized as three-dimensional with consideration of columns, superstructures, and abutment conditions. Three components of ground motion, corresponding to bridge's longitudinal, transverse, and vertical direction and their combinations are used to investigate bridge collapse. Studies indicate that bridge collapse is dominantly caused by transverse ground motion and the consideration of three-dimensional ground motion leads to a more accurate assessment. Failure mechanism of flared columns is analyzed applying nonlinear finite element method. Reduction of column capacity is observed due to orientation of flare. Further investigation demonstrates that the effects of flare play an important role in predicting of bridge failure mechanism. Suggestions are offered to improve the performance of bridges during severe earthquake.