Influence of gap width on buffeting force spatial correlation and aerodynamic admittance of twin-box bridge deck

Wind tunnel tests, including pressure measurement and Particle Image Velocimetry (PIV) test, have been carried out on twin-box bridge decks with four different gap widths (two small gap widths and two large gap widths). The effect of gap width on the buffeting force coherence and aerodynamic admittance of twin-box bridge deck are presented and discussed. The mechanisms of related experimental result are discussed in detail based on the pressure distributions and flow structures obtained in the tests. The measurements reveal that under the influence of vortices shed from the rear edge of the upstream box, the spanwise coherence of buffeting force on the downstream box decrease significantly with the increase of gap width, leading a sudden reduction in total buffeting force coherence on the twin-box bridge deck. While the aerodynamic admittance of twin-box girder increases conspicuously with the increase of gap width due to the generation of the local flow separation at the leading edge of downstream box for large gap width cases.