EXPERIMENTAL STUDY ON FLEXURAL BEHAVIORS OF STEEL-UHPC COMPOSITE GIRDER AND STEEL-CONVENTIONAL CONCRETE COMPOSITE GIRDER

The steel-ultra-high performance concrete (UHPC) composite girder, which is composed of UHPC slab and steel girder, has the advantages of light self-weight, high cracking resistance and durability, and it is of great significance for the development of steel-concrete composite girders. To investigate the difference of mechanical performance of a steel-UHPC composite girder and steel-conventional concrete under bending, in this paper, a trial-design of steel-UHPC composite girder bridge was carried out based on the prototype structure of a practical steel-concrete simply supported composite girder bridge, according to the trial-design results, the experimental study on flexural behaviors of steel-UHPC composite girder and steel-conventional concrete composite girder were carried out. Test results show that flexural behaviors of two kinds of composite girder were similar. Both of their failure modes were that the bottom flange of steel girder was yielded first, and then the upper concrete of slab was crushed. Compared with a steel-conventional concrete composite girder, under the condition of equal ultimate flexural capacity, the slab thickness of steel-UHPC composite girder can be reduced by 28%, and the ductility is better. The shear lag effect and the relative slip between steel girder and concrete slab of steel-UHPC composite girder are much smaller than those of a steel-conventional concrete composite girder. Moreover, the flexural stiffness of the two kinds of composite girder are close in an elastic range. However, due to the decrease of total depth of a steel-UHPC composite girder, its flexural stiffness is some smaller in an elastic-plastic range. The research findings of this paper can provide a reference for further study and engineering practice.