Bending Behavior of Composite Girders with Cold Formed Steel U Section

A new type of steel and concrete composite bridge with steel U-shape girders has been proposed. The U girder can be cold formed from one steel sheet, and the amount of welding required is substantially small and mass production could be possible. This new bridge would be therefore very economical. The steel U girder is composite with the reinforced concrete slab at the span center, whereas concrete is poured into the steel U section and prestressed at the intermediate supports of a continuous bridge. Bending tests were carried out to investigate the static bending behavior of the girder models. The girder model at the span center behaved as a composite beam. The girder model at the intermediate supports behaved as a prestressed beam and the filled concrete restricted the local buckling of steel plates in compression. A design calculation method for the girder section has been proposed assuming the Bernoulli-Euler principle, and was verified by the test results. This study shows that the new composite girder has sufficient bending strength and deformation capacity, and this bridge system is practical and feasible.