Strengthening of fatigue cracks in steel bridges by means of adhesively bonded steel patches

Steel bridges with orthotropic decks are a common construction method for long-span bridges. The type of construction was developed in the 1960s, and the early structures in particular show increasing crack damage. The reasons for this are, on the one hand, design deficiencies and, on the other hand, massively increased traffic loads. Therefore, there is a need for rehabilitation methods that neither weaken the cross-section, like bolted solutions, nor introduce thermal stresses, like welds, but so far there are no reliable and economic alternatives. This paper summarizes the state of the art on possible damage categories of orthotropic bridge slabs and presents a new rehabilitation alternative using bonded steel patches for crack rehabilitation. It is reported from an ongoing research project how to determine numerically the effectiveness of the bonded steel patches. For this purpose, simple analytical calculations are first used to determine the determining factors and to record their influence. Subsequently, nonlinear numerical calculations with the Drucker-Prager material model are used to identify the stress distributions in the bonded joints in order to optimise the patch geometries. To this end a stiffness factor is presented that can be used to classify such patch bonds and categorize them in terms of their effectiveness.