Mechanical behaviour of composite girders subjected to hogging moment: Experimental study

In continuous composite steel-concrete structures, cracking of the concrete slab in the hogging moment region decreases the global stiffness of composite steel-concrete structures and reduces the effect of continuity, thus making the structural behaviour highly nonlinear even for low stress levels, so special consideration is necessary. An experimental investigation on the behaviour of steel-concrete composite beams in hogging moment region is presented in this paper. A total of four specimens were tested under point load in the mid-span. Two of the composite beams with headed studs as the shear connectors, while the other two specimens are using Perfo-Bond Strips (PBLs) as the connection devices between the steel girder and the concrete slab. Ultimate load bearing capacity of composite sections in negative moment region was calculated and compared with experimental values. Crack formation, crack widths development process and strain distribution of the composite section before and after cracking were observed and presented in this study. Interface slip distribution was also given. Research results indicate that the current specifications such as AASHTO, JSCE, and EUROCODE-4 can provide appropriate values for ultimate strength of a composite girder under negative bending moment.