Structural Analysis of Suspension Bridges

Numerical procedures, suitable for digital computers, are given for analyzing suspension bridges under arbitrary conditions of live loading and temperature effects. The technique of analysis is to treat the cable, suspenders, and deck as forming a special type of open panel truss. By allowing for tower flexibility, a rigorous method of including the interaction between side and main spans has been obtained. Three distinct methods of bridge analysis have been given, each differing from the others in the choice of variable used for formulating the governing equations. The variables chosen were: Cable displacements, hanger tension, and stiffening girder bending moments. Corresponding to each method, an iteration routine is presented for solving the nonlinear governing equations. As might be expected, these show differences in the computational effort required to generate answers of specified accuracy. All three methods do, of course, generate identical results. Finally, the results of solving a long span bridge by all three methods are given, and these are compared with the values obtained by more conventional means.