Aerodynamics and surrounding flow patterns of a long-span bridge girder model with triple-separated boxes

The triple-box girder is finding broader applications in super long-span bridges for its excellent performance of flutter stability and traffic adaptability. In the present study, a bridge girder model with three separated boxes is experimentally investigated in detail via wind tunnel tests. In consideration of web modifications and accessory structures, the multi-point surface-pressure measurement and smoke-wire flow visualization are applied to investigate the aerostatic characteristics and flow structures. The "dual-frequency" phenomenon is found and explained for the bare girder with curved webs. For the present girder with linear webs, the global field is dominated by the separated-shear-layer instability. For the bare girder with curved webs, the upstream gap flow is dominated by the separated-shear-layer instability while the downstream gap flow is dominated by the double-shear-layer instability. The downstream gap flow exhibits obvious intermittent characteristics. In addition, non-Gaussian characteristic analysis of the surface wind pressures is introduced and improved for engineering practice. The distinguishing principle based on the skewness and kurtosis has high adaptability to both the bare girder and the completed bridge. In addition, semi-linear webs show better drag reduction. Combinations of accessory structures are also studied. The results show that during the construction process, prioritizing the installation of highway wind barriers can optimize the aerostatic performance of bridges. The present study embraces the booming era of long-span bridges with a triple-box girder and enriches the studies of bridge aerostatics.