Timber vs. Steel Bridge Superstructure Construction: A Simplified Structural, Economic and Environmental Analysis

For thousands of years, bridges were constructed primarily of timber. Then, in 1779, the first cast iron bridge was built, followed by the first primarily steel bridge in 1874. By the 20th century, wood had fallen completely out of favor for all major infrastructure projects. This thesis examined if such a wholesale shift to steel is still sustainable today given increased concerns about social and environmental impacts, particularly in light of modern advances in engineered wood products. Focusing on single span highway bridges in Vermont, structural models were created to determine appropriate section sizes for functionally equivalent steel and glued laminated timber sections. Methods for performing economic and embodied energy analyses were then proposed. While final conclusions regarding the relative benefits of steel and timber were not reached, it is believed that this three-pronged approach will ultimately allow for a nuanced and multi-faceted view of the benefits and costs associated with each material, allowing for more informed infrastructure planning