Reduction of vortex-induced oscillations of Rio-Niteroi bridge by dynamic control devices

Cross-winds of relatively low velocities have often set into vortex-induced oscillations the lightly damped and remarkably long three continuous spans of the steel twin-box-girder Rio-Niteroi bridge. Whenever this happens the bridge is closed to traffic of any vehicle, for the sake of user's comfort and overall safety. However, because of inherent operational difficulties, in some of these events the traffic barrier is closed too late and users are left frightened when crossing on the oscillating bridge. This deterrent aspect of the worlds largest steel-box-girder bridge is explored herein to briefly present the conceptual design of passive and active control devices to attenuate the observed oscillation amplitudes. For this an appraisal of the actual bridge dynamic behaviour is made first by using an experimentally calibrated mathematical-numerical model, including correlated aeroelastic forces along the spans. The derived dynamic modal equations, are further combined with optimization techniques to assist in designing feasible mechanical and robust dynamic passive and active control devices, to upgrade the serviceability of this bridge and user's comfort. The performance of these dynamic energy absorbers is demonstrated through comparison of numerical results obtained for time responses of the original and the controlled structure. (C) 2000 Elsevier Science Ltd. All rights reserved.