Experimental Study on Steel-Concrete Composite Twin I-Girder Bridges

A large number of steel-concrete composite twin I-girder bridges have been built in both Europe and Japan, but the lack of redundancy has always been a concern in the US and many other countries. In addition, very few experimental studies have been performed on mechanical performance of such bridges, particularly for the intact twin I-girder bridges. On this background, a steel-concrete composite twin I-girder bridge specimen was designed according to the current highway bridge design specification in Japan. Static loading tests were performed, and two loading conditions including both symmetric loading and asymmetric loading were applied. The load versus deflection relationship and strain development on the steel main girders and concrete slab at key sections were measured. The flexural strains on the lateral beam were also measured and reported in this paper to confirm the load transfer between two main girders. In addition, the shear strain of shear connectors (stud, in this study) was also measured to investigate the shear force transmission on the steel-concrete interface. The theoretical values were also provided to compare with the test results from the twin girder specimen under symmetric loading condition. The experimental results indicate that the theoretical analysis can predict the behavior of the twin girders very well in the elastic stage by considering the effective width of the slab. The performances of each structural component and load transfer path in such bridges were also discussed.