Sensitivity of Dynamic Response of Bridges under Multiple Hazards to Aging Parameters

Continued aging and deterioration of bridges poses a threat to bridge performance not only under regular service loads, but also results in pronounced vulnerability under extreme dynamic loads, such as seismic or hurricane induced surge and wave loading. In fact, aging of bridges in the form of corrosion attacks load paths critical under dynamic loads, including the superstructure-substructure connection elements and the reinforcing steel in column plastic hinge zones. This paper investigates the effect of aging on the dynamic response of multiple span concrete girder bridges when subjected to seismic as well as coupled surge and wave loading induced by hurricanes. The paper highlights the key differences and similarities in the nature of loads under the two natural hazards, the demand placed on key components, and the resulting dynamic response and failure modes of aging bridges. Nonlinear dynamic analysis is conducted using 3- dimensional bridge models with time-varying model parameters due to corrosion of reinforcing bars in decks and columns and degradation of elastomeric bearings with steel dowels. The sensitivity of component response, such as column demands, bearing deformations, or deck displacement, to variation in aging parameters is investigated in the study. Findings indicate that while the nonlinear dynamic behavior and select failure modes of the bridges may differ between the seismic and surge/wave loading cases, there is some consistency in the impact and criticality of aging parameters affecting dynamic response under the extreme loading cases, such as corrosion of bearing dowels and column reinforcement. These results form the foundation for multi-hazard vulnerability assessment of bridges considering the present in field condition.