Nonlinear Coupling in Cable-Supported Bridges for Non-Analogous Modes

It has been shown that the nonlinear differential equations representing the structural system of a suspension bridge exhibit nonlinear modal coupling that can lead to large torsional vibrations of the bridge deck. Such nonlinear coupling could play a role in the stability of cable-supported bridges under wind effects. Therefore, this paper presents an investigation of nonlinear modal coupling in cable-supported bridges with an emphasis on coupling between pairs of non- analogous modes, i.e., modes having a weak correlation along the bridge deck between the verti- cal displacement and torsional rotation. A procedure for assessing nonlinear coupling that relies on nonlinear generalized stiffness parameters is utilized for this purpose. Results of nonlinear gen- eralized stiffness analysis for suspension bridges indicate that non-analogous modes have a weak- er nonlinear coupling compared to analogous modal pairs.