A simple method using a truss model for in-plane nonlinear static analysis of a cable-stayed bridge with a plate deck section

A beam element is simulated by a plane truss, which exhibits the same axial and flexural stiffness. A short computer program has been developed for the nonlinear static analysis of a plane truss model of a beam structure, with incremental loading. The geometric nonlinearities, due to large displacements interacting with large axial forces, are taken into account by writing the equilibrium equations with respect to the deformed truss. The proposed truss model and computer program are first shown to predict the deformations and reactions of simple beams. Then, they are applied to a typical cable-stayed bridge of medium size with a plate section of the deck. A multi-cable model is used, where every cable in the model represents one individual cable of the real bridge. This detailed model can accurately predict the small bending moments and deformations of the deck, which allow the use of a slender plate section. The results of static analysis of the bridge by means of the proposed model and program are compared with corresponding published results for the same bridge given by Walther and co-workers [Walther R, Houriet B, Isler W, Moia P, Klein JF. Cable-stayed bridges. 2nd ed. Th. Telford; 1999], as regards axial forces and bending moments in the pylon and deck, as well as deformations of the deck, for various combinations of live loads, and are found to be in a satisfactory approximate agreement with them. So, the proposed truss model and computer program are proved reliable and can be used in the preliminary design of cable-stayed bridges.