Evaluation of ultimate strength of rational and economical bridges for performance based design

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Recently, some types of rational and economical bridges are proposed for reducing the construction cost of bridges. U-shaped steel girder is one of proposed rational and economical bridges. The ultimate strength of U-shaped steel bridge girders under construction is inferior to that after construction. But the ultimate strength of U-shaped steel girders without the slab under construction is not obvious and it is not clear whether previous design method for I-shaped steel girders is applicable to the U-shaped steel girders.In this research, the bending and shear experiments of U-shaped steel girders were carried out in order to grasp the feature of ultimate strength and to get the basic data for confirming adequacy of FEM analyses used in this study. The test specimens were made in consideration of the structural parameters of actual U-shaped steel bridge girders. Besides experiments, FEM analyses were conducted for investigating the feature of ultimate strength of U-shaped steel bridge girders in detail. On the basis of experimental results and analysis results, the evaluation method of bending strength shear strength of U-shaped steel bridge girders were proposed. The validity of the proposed evaluation method was confirmed in comparison between calculated values by the proposed evaluation method and not only experimental results but also analysis results.