Theory and History of Suspension Bridge Design from 1823 to 1940

Within the context of a historical overview, this paper examines how the history and theory of suspension bridges affected their design between 1823 and 1940. Navier's theory of the unstiffened suspension bridge reveals the concept of cable stiffness. The experience of wind-induced motion in 19th century bridges was a primary influence in the adoption of the stiffening truss, and the Rankine theory, which first considered such trusses, resembles a simple beam solution. The subsequent elastic theory as shown in this paper also resembles a simple beam solution. A reformulation of the deflection theory presented here allows for a physical interpretation and comparison to the previous theories. In examining these theories, this paper gives results of sample calculations based on the Monongahela, Delware River, and George Washington Bridges; these specific examples reveal certain properties of the theories that emphasize the importance of physical understanding to the use of mathematical theories.