Aerodynamic characteristics of a 2-box girder section adaptable for a super-long span suspension bridge

According to the previous investigation on the suspension bridge with a 2-box and 1-box combined girder, which is newly developed to apply to the super-long span bridge having a main span of 2500 m or more, it is indicated that unbearable large torsional displacement induced in the high wind velocity and decreased flutter stability are the problems to be solved. This paper deals with the investigation of an improvement of steady pitching moment characteristics on the girder cross section to decrease the torsional displacement under wind loads, and also an improvement of flutter stability. As a result of investigation on the 6-lane-type girder, it is found that the steady pitching moment characteristics and flutter stability can be improved by attaching rails for an inspection cab to the bottom of fairing and by attaching vertical plates to the lower flange of the girder. Furthermore, a study is conducted on the subject of a 4-lane-type girder having similar cross section to the 6-lane-type girder section.