WASHINGTON D.C. — A new research report issued by the University of Wyoming evaluates the life cycle sustainability (cradle to grave) of two functionally equivalent steel and concrete rural bridges. The study was conducted by Michael Barker, Ph.D., P.E., professor of civil and architectural engineering at the University of Wyoming, and research students Sarah Bridges, Ione Chandler and Peyton Smith.
The two functionally equivalent bridges used within the study are two-lane, approximately 35-ft.-long simple spans, located in Whitman County, Washington, and built with local crews. Only the superstructures of the bridges were considered in the analysis. Four criteria were developed to evaluate and compare the sustainability of the two bridges:
- Embodied carbon emissions of materials, and emissions from equipment
- Embodied energy of materials, and energy consumption from equipment
- Waste management and recyclability
- Life cycle cost
The outcome shows that, over the life cycles of the two bridges, the concrete bridge:
- Results in 26.3% more embodied CO2e (carbon dioxide equivalents) emissions
- Results in consumption of 8.7% more energy
- Results in recycling of 17.8% less material (at the end of its service life when compared with the steel bridge)
The concrete bridge also has a life cycle cost that is 23% higher than the steel bridge.
Dan Snyder, director of business development for the American Iron and Steel Institute and director of the Short Span Steel Bridge Alliance, said: “The potential environmental impact of bridges has become an important consideration when selecting materials for a crossing, but there is limited information available on how to evaluate and compare the life-cycle sustainability of materials used for the superstructure of a bridge. To address this inadequacy, we asked Dr. Barker and his team to take a close look at these two functionally equivalent bridges.”
Snyder noted: “This is a first attempt to analyze a steel and concrete bridge in a life-cycle sustainability study, and the results may vary when making other bridge comparisons. However, this study provides a positive first step toward developing a methodology to analyze future bridges, which could become an important tool for bridge owners seeking to make sustainable choices for their projects, especially as funding for rural bridge projects becomes available through the Bipartisan Infrastructure Law.”