Rating and Preliminary Analysis of Suspension Bridges

Formulas for different loading cases of suspension bridges are presented. Although theoretically not correct, the principle of superposition can be used to get practical answers that are sufficiently accurate for determining stresses, deflections, and rotation in a stiffening truss or girder. The horizontal cable tension H is computed using the more accurate method by Steinman or the approximate method by Tsien. With H known, the differential equation for the various loadings can be resolved, and the results of such computations are shown in this paper. A numerical example is worked out to clarify the mathematical procedure. The data are from the Angostura suspension bridge over the Orinoco River in Venezuela.