Effect of bond layer thickness on behaviour of steel-concrete composite connections

The performance of steel-concrete composite structural members depends on the connection at the steel-concrete interface. Structural adhesives are gaining rapid recognition as the bonding material between steel and concrete interfaces. The thickness of adhesive layer in a composite connection plays a key role in maximising the bond capacity. In this paper, the effect of the change in thickness of adhesive layer on the capacity of connection, ultimate slip at the interface, and the shear stiffness of connection have been studied. Twenty-five test specimens were cast and tested under direct shear to achieve the optimum thickness of adhesive layer. The ultimate strength and relative slip of all five adhesive layer thicknesses of steel-concrete specimens, obtained through experimental studies, were verified using finite element analysis. The failure patterns of bonded connection were also critically observed and found to be varying with adhesive layer thickness. It changes from adhesive failure to mixed (adhesive and cohesive) failure, and from mixed failure to cohesive mode of failure, with increasing thickness. At the optimum thickness, the composite interface experiences a mixed mode of failure. The effectiveness of bonded connections over mechanical shear stud connections was outlined through a comparison of the load-slip behaviour of both.