This article reports an experimental study to characterise the concrete–steel bond under repeated loading. Three loading patterns, namely partial unloading, full unloading and multiple unloading were performed. In addition, the non-linear bond behaviour of the concrete–steel interface was studied whereby the initial elastic bonding, non-linearity and softening behaviour of the interface were simulated in a numerical analysis. The complete tangential traction–slip curves, as well as the unloading/reloading routes in the repeated loading cases, were calculated and compared with the experimental curves. 3D interface elements and a damage model are used in the numerical analysis. The small number of 3D interface elements used and the high accuracy achieved by the numerical simulation ascertained the viability of the proposed approach for analysing composite structures.