To optimize the cross section of steel box girder of the Xihoumen bridge, a suspension
bridgewith amain span of 1 650 m, the aerodynamic performance of twin-box cross sections slotted
respectivelywith awidth of5. 5, 6. 0 and 6. 5 m were simulated numericallywith the computational
fluid dynamics (CFD) method. The numerical simulation indicates that the aerodynamic performance
of the twin-box cross section slotted 6. 0m wide isbes.t The critical flutterspeedsof the twin-box cross
section slotted 6. 0m wide, a traditional single box cross section and a twin-box grid cross sectionwere
measured by 1∶80 section model tests, and their aerodynamic performances were discussed. The
experimental result shows that the three kinds of cross section can meet the requirement for flutter
speed of78. 2 m/s, but it is necessary to adopt aerodynamic controlmeasures to a traditional single
box cross section