Experimental study of wind-field characteristics and torsional vortex-induced vibrations for a split three-box deck sitting above water waves

Abstract

The wind-field characteristics of a split three-box deck sitting above water waves and its torsional vortex-induced vibrations (VIVs) were experimentally investigated using wind-tunnel and wave-flume tests. The wind field was measured using turbulent flow instrumentation (TFI) Cobra probe. To test the VIVs of the split three-box deck, a test system that could elastically suspend the deck sectional model by eight springs and guarantee free oscillation of the deck sectional model only in the heaving and torsional directions was constructed. The test results indicated that the regular wave height (H) and regular wave period (T) mainly promoted the overall turbulence-intensity (Iuvw) and turbulence-intensity component (Iw). These contributions were further strengthened by an increase in H and a decrease in T, respectively. In general, the variations in Iuvw and Iw, particularly the latter, should be regarded as the major cause of the change in the maximum torsional VIV amplitudes of the deck sectional model with a scale ratio of 1:60 when compared to the mean local wind speed (U) and wind-speed component (w). The differences in these amplitudes under different cases in the first lock-in regions were not evident, whereas those in the second lock-in regions were significant. In the second regions, the smaller the relative bridge clearance (a/H), the smaller the maximum torsional VIV amplitudes, and the maximum torsional VIV amplitudes increased with T, which were all smaller than those in the corresponding wind-only case. Moreover, the larger the bridge clearance (a), the larger the maximum torsional VIV amplitudes in the wind-only cases (a = 0.30, 0.42, 0.50, and 0.58 m). Evidently, the presence of water waves is conducive to the suppression of torsional VIVs of the split three-box deck when VIVs occur.