A new type of steel and concrete composite continuous girder bridge is developed using steel U-section as main girders, in which steel U girder is composite with RC slab in span center where positive bending moment is critical, whereas concrete is poured into the steel U-section and pre stressed at the intermediate supports where negative bending moment is critical. Experiments and analysis are carried out to investigate the static bending behaviors of this new girders. It is found that composite action can be attained for the positive bending moment portions, steel section and pre-stressed concrete work as one piece for the negative bending moment portions, and calculations based on the RC method has good agreement with experimental data. A trial design is also conducted taking three-span continuous girder with span of 60m, which shows that the new bridge system can be economical.
