Multihazard Damage and Loss Assessment of Bridges in a Highway Network Subjected to Earthquake and Tsunami Hazards

The objective of this study is to examine and compare the vulnerabilities of highway bridges to the combined effects of earthquake shaking, ground failure, and tsunami loading. Earthquake-induced ground shaking, ground failure (e.g., landslides and liquefaction), and tsunami inundation fragility functions are combined with regional hazard data to estimate the damage to bridges in a highway network, direct economic loss, and reduction in traffic capacity. The proposed framework is applied to all bridges listed in the National Bridge Inventory (NBI) and located in the state of Oregon for several earthquake scenarios developed for the Pacific Northwest region of the United States. A parametric study is performed to understand the sensitivity of economic loss and postearthquake traffic capacity with respect to various fragility function classes as well as the parameters defining these fragility curves. Results show that the predicted damage varies substantially depending on the class of fragility function used. In addition, the loss estimates show significant sensitivity with respect to parameters defining the fragility functions, particularly the resistance models, emphasizing the need to develop specific and systematic regional fragility curves for bridges. The results also indicate that when ground failure and tsunami inundation are jointly considered, there is a significant increase in the loss estimates when compared to the estimates obtained from when ground shaking is considered alone.