Effects of various modeling uncertainty parameters on the seismic response and seismic fragility estimates of the aging highway bridges

This paper proposes an alternative time-dependent seismic fragility assessment framework for aging highway bridges considering the non-uniform chloride-induced corrosion and various modeling uncertainty parameters. Firstly, sensitivity analysis with the tornado diagram technique is performed to determine the sensitivity of some typical bridge engineering demand parameters (EDPs) to 22 modeling related uncertain parameters, and then 10 critical parameters are identified. Subsequently, based on a series of nonlinear time history analyses (NLTHAs) on the sample models generated by using the Latin hypercube sampling (LHS) method, comparative studies for the time-invariant and time-evolving seismic response, as well as the time-dependent seismic fragility estimates incorporating different levels of uncertainty are performed, respectively. It is concluded that (1) the uncertainty of the modeling related uncertain parameters may lead to the difference in the trajectory of seismic hysteretic response for a given bridge member, whereas the variation of the peak value of seismic response may result from the couple contributions of the uncertainty of ground motions and modeling related parameters; (2) the inclusion of only ground motion uncertainty is inadequate and inappropriate, and the proper way is to incorporate the uncertainty of the identified critical modeling parameters and ground motions into the time-evolving seismic response and the time-dependent seismic fragility assessment of the deteriorating highway bridges.