There are decades of studies demonstrating the effectiveness of wildlife overpasses and underpasses in conjunction with fencing to reduce wildlife-vehicle collisions and provide ecological connectivity. Current materials used to build these structures are primarily concrete and steel, which can result in high costs due to increased construction time, maintenance, and a relatively short service life. Recently, engineers and architects are finding fiber-reinforced polymer (FRP) composites as an alternative material for bridge structures due to their high strength-to-weight ratio, accelerated bridge construction methods, and low life-cycle costs over its estimated 100-year service life.
FRP is better suited to withstand environmental conditions compared to concrete and steel, and they are more corrosion resistant – which can reduce costs and time-consuming traffic detours for maintenance. The carbon footprint of the FRP materials, combined with its transportation and construction efficiencies, can be lower than traditional building methods. Although fibers held together with virgin resins are commonly used in FRP materials today, current research is developing more sustainable bio-based and recycled materials for use in the future. FRP bridges can support the static and dynamic loads of vehicle traffic, making them more than capable of supporting the lighter and less demanding loads required for wildlife crossing structures.
This project is designing the first FRP composite wildlife overpass in North America. The site location is northern California in Siskiyou County along U.S. Highway 97. The California Department of Transportation (Caltrans), Animal Road Crossing (ARC) Solutions, and other state and local stakeholders are partners in the development of the FRP wildlife infrastructure.
To date, the project’s research team has published a journal article reviewing the feasibility of FRP wildlife infrastructure, interviewed design professionals, and investigated potential North American FRP manufacturers. The research team, along with Caltrans, have selected FRP tub girders manufactured by Advanced Infrastructure Technologies (AIT) for the main bridge span. A design charrette was conducted with landscape architects, engineers, ecologists, and other professionals to identify additional applications of FRP materials beyond the structure itself (e.g. sound/light barriers, fences, jump-outs, habitat, cover, etc.). These FRP elements will complement the overall design objectives by introducing more sustainable and recycled materials. The FRP overpass concept will be used to conduct a 100-year cost/benefit analysis to see how FRP compares to common materials like concrete and steel. The analysis will help Caltrans make a bridge-type selection – with the hopes FRP will be the best long-term solution for building wildlife infrastructure. The research team will be presenting a research update in poster format.