Eco-Structure Design

Asif, Ruhul and Tamjid are investigating the overall advantages of optimized long-span girders for the Tanana River Bridge near Tok, Alaska. While extending girder spans reduces the number of required piers and foundations, the increase in superstructure material is not entirely balanced by the reduction in substructure materials. In fact, the cost of superstructure materials can exceed that of shorter spans by more than 1.5 times, with only partial compensation through savings in the substructure. Nevertheless, the secondary benefits of longer spans are significant: fewer piers reduce disruption to natural water flow, mitigate scouring, and promote healthier aquatic ecosystems and riparian vegetation. Additionally, the reduced number of piers and foundations leads to shorter construction durations and lower long-term maintenance costs. This study aims to quantify these comprehensive benefits to support the case for adopting optimized longer girder spans for the Tanana River Bridge and for any bridge in general.