Performance analysis on Twin-I girder bridges using hollow tubular top flanges

Twin-I girder bridge systems have advantages including simplified construction process and less material cost. However, due to the weak torsion stiffness of I section, the systems using I-girders requires many cross frames and individual I girder cannot erect without interior cross frame installation. The use of I sections with a hollow tube as the top flange increase the torsion stiffness, which can improve the stability and strength of bridge systems. In the paper, twin-girder bridges systems using traditional I-girder and hollow tubular flanges are studied to provide the differences among them. The analysis results show that the stability of girder with hollow tubular flange is much larger than traditional I girder, which has less requirements for girder erection and needs of interior diaphragms of girder system. Parameters are studied including flange width-to-thickness ratio, web depth-to-thickness ratio and reasonable girder depth. Some recommendation for the design of steel I-girders using hollow tubular flanges are given.