Identification of aeroelastic forces on bridge cables from full-scale measurements

Despite much research in recent years, large amplitude vibrations of inclined cables continue to be of concern for cable-stayed bridges. Various mechanisms have been suggested for their excitation, including rain-wind excitation, dry inclined cable galloping, high reduced velocity vortex shedding and excitation from the deck and/or towers. Although some experiences have been done with full-scale measurements of inclined cables, many of the results available are based on wind tunnel tests and theoretical modelling. This paper presents results from full-scale measurements on the cables of the Øresund Bridge. The system records wind conditions and weather conditions, as well as accelerations of certain cables and a few locations on the deck and tower. Using state-of-the-art methods of output-only system identification, the vibration modes of the cables have been identified. From these modes, the aeroelastic forces acting on the cables are identified and in particular their total effective damping and stiffness matrices. A comparison between damping matrices identified from experimental data of the cables accelerations and theoretical data based on quasi-steady theory and on wind tunnel data from two different cables have been made.