Seismic life-cycle cost analysis of ageing highway bridges under chloride exposure conditions: modelling and recommendations

Abstract

Chloride-induced corrosion of highway bridges constitutes a critical form of environmental deterioration and may result in significant escalation of seismic life-cycle costs due to increased fragility during earthquake events. Most of existing literature tends to adopt simplistic uniform area loss assumptions in lieu of potentially complex, yet realistic and more detrimental, pitting corrosion models for seismic vulnerability analysis. Since the degree of deterioration depends on the severity and duration of exposure, there exists a need to investigate the influence of uniform vs. pitting corrosion assumption on seismic life-cycle costs for varied chloride exposure conditions. A case-study example of a highway bridge in Central and Southeastern US reveals consideration of pitting corrosion as critical for extreme exposures compared to relatively minor settings. Subsequently this study provides recommendations to aid bridge engineers and stakeholders to balance between computational cost and accuracy of results to aid prompt decisions on rehabilitation of ageing bridges in different exposure conditions. A framework is also included to compute seismic life-cycle costs from generic measures of corrosion, independent of assumed exposure scenario. This framework is particularly helpful for seismic loss assessment of highway bridges in chloride exposure zones with periodic field measurements to estimate the extent of structural deterioration.

Keywords:

• Seismic analysis
• chloride-induced deterioration
• uniform vs. pitting corrosion
• time-dependent seismic fragility
• deicing salt exposure
• marine exposure
• field-instrumentation data

Acknowledgments

This research was funded by grant number 14IRTAPSG008 from Industrial Research and Consultancy Centre at Indian Institute of Technology Bombay. The support is gratefully acknowledged. Additionally, the contributions of the third author were supported by the National Science Foundation (NSF) under grant number CMMI-1055301. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.