"A flexible multi-body model for the dynamics and aeroelastic stability of cable-supported bridge cross-sections."

The complex three-dimensional dynamics of suspension and cable-stayed bridges can be strongly characterized by the structural interactions among the bridge deck and the sustaining cables, namely the hangers or stays. Motivated by the inherent shortcomings of the common single-body section models, the paper presents a flexible multi-body model able to describe – in the cross-section plane – the linear and nonlinear terms of geometric coupling between a principal body, whose rigid roto-translations simulate the global components of the bridge deck motion, and two secondary bodies, with small point masses, whose displacements simulate the transversal component which dominates the local motion of a cable pair. Different aspects of the multi-body model dynamics are investigated, by means of perturbation techniques. First, a multi-parametric sensitivity analysis of the linear modal properties is performed, with particular regard to internal (1:1) resonance conditions which may give rise to multiple veering phenomena between two or more frequencies, associated to a complete hybridization process of the corresponding global and local modes. Second, the nonlinear mechanisms which determine high-amplitude low-frequency oscillations in the cable local motion are analyzed, with focus on the autoparametric excitation given by the low-amplitude high-frequency global vibrations if sub-harmonic (2:1) resonance conditions occur between a global and a local mode. Third, the aeroelastic stability of the dynamic system when a stationary wind flow acts on the doubly-symmetric cross-section of the principal body is studied, especially in respect to the stabilizing or destabilizing effects of internal resonance conditions on the critical wind velocity which may cause the onset of torsional galloping phenomena.