Abstract
To investigate the spanwise correlation of vortex-induced forces (VIF) of a typical section of a streamlined box girder, wind tunnel tests of simultaneous measurement of force and displacement responses of a sectional model were conducted in a smooth flow. The spanwise correlation of VIF and pressure coefficients on the measurement points of an oscillating main deck were analyzed in both the time domain and frequency domain, respectively. The research results indicated that the spanwise correlation of VIF and pressure coefficients on the measurement points were related to the amplitudes of vortex-induced vibration (VIV), both of them weakened with the increase of spanwise distance; the maximum value of spanwise correlation coefficient is situated at the ascending stage of the lock-in region, rather than at the extreme amplitude point. The amplitudes of VIV showed different impacts on the spanwise correlation of pressure coefficients on the measurement points of the upper and lower surfaces, for which the maximum value of the spanwise correlation coefficients is located at the extreme amplitude point and the ascending stage of the lock-in region, respectively. Furthermore, the spanwise correlation of the pressure coefficients decreases continually from the upstream to downstream of the main deck; large coherence of vortex-induced forces and pressure appears around the frequency of vortex shedding, and the coherence of VIF and pressure becomes smaller with the increase in the spanwise distance.
Highlights
With the continuous increase in span lengths, long-span bridges are characterized by their large flexibility and low damping, and more sensitive to the wind-induced vibrations, which is the primary concern for the serviceability and safety issues of the bridge
As for the representative pressure measuring points on the upper surface, the spanwise correlation of the pressure coefficient in the ascending stage (V2–V3–V4) of the lock-in region increases with the increase in vortex vibration amplitude. e maximum spanwise correlation coefficient of the pressure coefficient is located at the extreme amplitude point (V5), rather than the other representative wind speeds in the ascending stage (V2-V3-V4) of the lock-in region. e descending point (V6) has a larger spanwise correlation coefficient of the pressure coefficient than that of the other three representative wind speed points (V2, V3, and V4) in the ascending stage of the lock-in region
E maximum spanwise correlation coefficient of torsional torque in the lock-in region is located at the third ascending point (V4), rather than at the extreme amplitude point (V5) of lock-in region
Summary
With the continuous increase in span lengths, long-span bridges are characterized by their large flexibility and low damping, and more sensitive to the wind-induced vibrations, which is the primary concern for the serviceability and safety issues of the bridge. To overcome the shortcomings of the wind tunnel test, researchers have attempted to accurately predict the VIV of bridges through three-dimensional (3D) full-bridge analysis In this process, the important work is to establish an accurate mathematical model of vortex-induced force (VIF). Xu et al [20] studied the characteristics of torsional VIV and the correlation between the surface pressure and VIF for a streamlined box girder using a small-scale section model. In order to further understand the characteristics of the fluctuating VIF and surface pressures on a typical streamlined box girder of bridges, in the current study, a 1 : 25 large-scale section model was adopted in the wind tunnel test to reduce the influence of Reynolds number.
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