Effects Of Vertical Clearance On Aerodynamic Characteristics Of Long-span Bridge Girders

Long-span bridges have different vertical clearance under the bridge due todifferent structure forms and different terrain. River-crossing bridges face significantwater surface fluctuation during the rainy season and dry season, while sea-crossingbridges may also be suffered from clearance variation due to climate and oceancurrents. These factors may present noticeable changes in vertical clearance under thebridge girder. Long-span bridges are flexibile with low damp ratio,which are therefore,sensitive to the wind. The influence on the aerodynamic characteristics of the bridgegirders due to changes in vertical clearance under the bridge have to be consideredduring bridge design. Few research is available on this issue.Hence this articlefocuses on the topic based on computational fluid dynamics (CFD) method with atwo-dimensional numerical simulation employed.Firstly, a two-dimensional numerical simulation of the flow around squarecylinder is employed to verify accuracy of the calculation methods. The resultsinclude strouhal number, aerodynamic mean force coefficient, the distribution of thesurface pressure coefficient and flow field characteristics. The calculation results arein good agreement with wind tunnel test, which indicates that the SST k model hasgood precision. Research on Reynolds number effect of the flow around squarecylinder suggests that in the range of order from1.0×103to1.0×105, Reynoldsnumber effect is not obvious.Then, the effects of vertical clearance on the aerodynamic characteristics of therectangular cylinder are investigated. A rectangular cylinder with the ratio of width toheight5is selected as research object. A two-dimensional numerical simulation of theflow around the rectangular section with different vertical clearance under thebridge.The results include aerodynamic mean force coefficient, the distribution of thesurface pressure coefficient, flow field characteristics, and et al. Comparing theresults of each condition, the specific impact of the vertical clearance on aerodynamiccharacteristics of the rectangular cross-section was clarified.Finally, the effects of vertical clearance on aerodynamic characteristics of thelong-span bridge girders are investigated. A closed steel box girder section of a realbridge was chosen as research object. A two-dimensional numerical simulation of theflow around the box girder section with different vertical clearance under the bridge is employed. The results include aerodynamic mean force coefficient, the distribution ofthe surface pressure coefficient, flow field characteristics, and et al. Comparing theresults of each condition, the specific impact of the vertical clearance on aerodynamiccharacteristics of long-span bridge girders was clarified.