Experimental research on the behaviour of concrete-to-concrete interfaces subjected to a combination of shear and bending moment

Results show that the load transfer capacity across the interface is reduced due to the bending moment crack opening, but it has no influence on the shear and the bending strengths of the beam specimen. However, the bending ductility of the latter is partially reduced due to a shear slippage occurred after the formation of a plastic hinge, and the collapse of the compression zone. It was not possible to evaluate the accuracy of the design expressions to predict the interface maximum friction strength. However, the general application of these expressions to this situation is doubtful, as they are incapable to predict the strength deterioration occurred after the yielding of the longitudinal reinforcement.