Ultimate behavior and strength of cable-stayed composite 2-I-girder bridges

Masatugu Nagai

This paper describes ultimate behavior and strength of cable-stayed bridges with a steel-concrete composite 2-I-girder and proposes stability design method of the main girder.

Using 150,400 and 600-meter span bridge models, their ultimate behavior and strength are studied based on elasto-plastic finite displacement analysis, in which the depth of the girder is chosen as a parameter.

Under the condition that min. depth of 1.0 meters is used for the bridge with a span length up to 400 meters, and max. span-to-depth ratio of 400 is used for the bridge with a span length from 400 to 600 meter, the followings are the results obtained from this study.

1）Geometrical non-linear effect is minor and can be neglected.

2）Global buckling behavior of the girder is not observed．Hence, stability check on global buckling is not necessary.

3）Ultimate strength is controlled by the yielding of the steel material．The load parameter（the ratio of the total load at ultimate state to the design load）can be calculated from the yield point divided by the max. working stress under design load．