Flexural behavior of steel-concrete composite beams with U-shaped steel girders

This paper focuses on a new type of steel-concrete composite beams consisting of U-shaped steel girders and angle connectors. Compared with conventional composite beams consisting of wide flange girders and headed stud connectors (or short channel connectors), the composite beams considered in this study have favorable flexural performance while reducing the excessive costs and potential construction challenges due to installation of the stud and/or channel shear connectors. Through four-point bending tests on five specimens, this research team experimentally investigated flexural behavior of such new composite beams. The five specimens were varied to have different angle connector intervals and installation locations. Test results showed that composite beams with angle connectors welded to the webs of U-shaped steel girder failed in brittle failure modes while composite beams with angle connectors welded on the top flange of U-shaped steel girder failed in ductile failure mode. Moreover, finite element analysis were performed and the results were verified by the experimental results. According to the parametric analysis results, concrete strength has little effect on flexural behavior of composite beams while increasing yield stress of steel girder could significantly increase the flexural resistance but could not change the initial stiffness. Increasing the height of steel girder, the thickness and width of bottom flange are recommended to improve the flexural behavior of composite beams.