A method for resilience comparisons of bridges and viaducts

Bridges and viaducts are primary assets on transport infrastructure systems. The recent failures of the Francis Scott Key Bridge and the Polcevera Viaduct have highlighted the need to regularly reconsider the resilience of bridges. The disruption to railways and seaways below these bridges has highlighted the need to consider all uses of the bridge, not just those on the structure. This paper outlines a new method to estimate the resilience, using data on the use of the bridge based on the number of road lanes, rail lines, footways or navigable waterways on or under the bridge as the measure of performance or functionality. The data for ten bridge collapses, with use functionality data and dates from which the restoration times are derived, are used to determine resilience. The results of the study show a correlation of increased resilience index with increasing restoration time. There is less correlation of resilience with bridge size based on number of lanes or lines. The consideration of all uses of the bridge (both over and under) can affect the calculated resilience index.