Analysis of longitudinally Loaded Suspension Bridges

A method is presented for analyzing multispan suspension bridges subjected to longitudinal loads that act in the direction of bridge axis. It was assumed that the loads acting directly on the suspended structure are sustained by the structure itself, and only the loads on the cable are considered. The interaction of consecutive spans and the cable movements at tower tops cannot be disregarded. To analyze each span of a multispan bridge as an independent single-span with immovable cable ends renders erroneous results. Loads in center-lying spans are transferred to end spans. In a long, multispan bridge, longitudinal loading causes cable tension and stiffening-truss bending moments that cannot be disregarded when compared with what will arise from live loads as shown in the example of a 5,000-m, five-span bridge. An example of a three-span bridge is also presented.