Cable Stayed Suspension Bridge Making Combined Use of One-Box and Two-Box Girders

A cable-stayed suspension bridge having characteristics of a cable stayed bridge and those of a suspension bridge at the same and time and using one-box and two-box girders in combination is disclosed. The bridge grinder of the cable-stayed suspension bridge includes one-box girders that each extend to both sides through the respective one tower and a two-box girder set in a central portion of the center span between towers in the length direction of the bridge girder. The cable-stayed suspension bridge includes cable-stayed structures in which a respective one of the one-box girders is supported by the tower with plural cables and a suspension structure in which the two-box girder is supported by the plural towers with two main cables and plural hanger ropes. The two-box girder has a central ventilation opening in the central portion as viewed in a transverse direction thereof. The hanger ropes in the suspension structure extend from the main cables almost perpendicularly, and their lower end portions are connected to the end portions in the transverse direction of the central ventilation opening or in the vicinity thereof.