"Dynamic interactions in cable-stayed systems"

The coupled motion of cables and other structural elements in cable-stayed systems may exhibit a variety of dynamic interaction phenomena. The veering of system natural frequencies and the localization or hybridization of the modal shapes may characterize the linear dynamics of these structures, whereas the cable geometric nonlinearities enable different mechanisms of auto-parametric excitation, which strongly affect the high-amplitude oscillation regimes. Both the occurrence and relevance of these phenomena are strongly depending on possible internal resonance conditions between the frequencies of local (cable) modes and those of global (main structure) modes. On this respect, many common structures, like for instance cable-stayed bridges, possess high spectral density of global and local frequencies even in the range of low frequencies, due to the flexibility and slenderness properties of the main structure (deck), and, concurrently, to the presence of quasi-periodic fans of high-tensioned stay cables. In the present paper some of the known linear and nonlinear interactions phenomena are studied through simple parametric models, which still allow to wholly capture the main features of the dynamic behaviour of the cable-stayed structures. Under a few simplifying hypotheses, the models linear spectral properties are obtained from closed-form analytical solutions. Parametric investigations are drawn to specifically study the model dynamics under different conditions of (multiple) internal resonance