Wind-Tunnel Investigations of the Aerodynamics of Bridge Stay Cable Cross-Sectional Shapes

Federal Highway Administration2021PDFTech ReportChristiansen, HeidiLarose, Guy L.National Research Council of CanadaUnited States. Federal Highway Administration. Office of Infrastructure Research and DevelopmentBosch, Harold R.United States. Federal Highway Administration. Office of Infrastructure Research and DevelopmentUnited StatesCable stayed bridgesBridge cablesVibrationHazard mitigationWind tunnelsHDPEPipe roundnessHelical filletsGallopingFHWA-HRT-21-074DTFH61-13-D-00011Bosch, Harold R.September 2014\u2013September 2016Experiments on stationary sectional models of scaled replica of bridge stay cables were carried out in a 2-by 3-m wind tunnel. The cross-sectional shapes of the cable models were obtained from direct measurements of stay cables for bridges in service. The purpose of the experiments was to establish a relationship between the level of eccentricity and surface irregularities of the cross-sectional shapes of stay cables and their propensity to experience wind-induced vibrations. The experiments confirmed that the aerodynamics of the stay cables are highly sensitive to their cross-sectional shapes. A small deviation from the mean curvature had an important influence on the aerodynamic force coefficients, in particular the mean across-wind force coefficients in the critical Reynolds number regime. Based on a quasi-steady analysis of the experimental results, negative aerodynamic damping in excess of 1 percent of critical could be predicted, confirming the propensity of stay cables to gallop for certain orientations to the flow, Reynolds numbers, and cross-sectional irregularities. Because of these experiments, researchers concluded that changes in across-wind forces as a function of angle of attack and Reynolds numbers could be the main contributors to anticipated wind-induced vibrations. Finally, this report discusses how such critical angles can be identified.119