The nonlinear static analysis of three-dimensional long-span cable-stayed bridges under the effect of their own dead weight and a set of initial cable tensions is formulated. All sources of geometric nonlinearity, such as cable sag, axial force-bending moment interaction in the bridge deck and towers, and change of the bridge geometry due to large displacements, are considered in the analysis. A computer program that uses a tangent stiffness iterative-incremental procedure is described to perform the nonlinear static analysis. Problems in modeling this special type of structure are addressed. Examples of three-dimensional mathematical models representing the present and future trends in cable-stayed bridge construction are presented. The results show that these flexible structures are highly nonlinear under dead loads, especially for very long span bridges. The analysis is essential to start linear or nonlinear dynamic analyses from the dead load deformed state utilizing the tangent stiffness matrix of the bridge under gravity load conditions. © 1990.
