STEEL WEIGHT OF BOX GIRDER WITH DIFFERENT STEEL STRENGTH FOR THOUSAND-METER SCALE CABLE-STAYED BRIDGES

The steel weights are compared between the four trial designs of cable-stayed bridges using different steels with yield point of 345MPa, 420MPa, 485MPa and 690MPa, named as Q345, Q420, HPS70W and HPS100W respectively. The trial designs of the bridge having an identical mid-span length of 1088m are considered having an identical relative safety factor described by the ratio of the longitudinal stress calculated to the yield strength of the box girder. The results indicate that the structural self weigth of the girder for thousand-meter scale cable-stayed bridges become lighter by the use of high performance steels and the steel weight can be reduced obviously with the increase of the steel strength, although the design stresses of some plates of the box girder are not govered by the matiral strength due to the influence of the stability of stiffened plate weights and the minimum plate thickness. The application of high performance steels can increase the span ability of cable-stayed bridges.