ABSTRACT
Many steel structures, such as road and rail bridges, have an enormous need for rehabilitation. In particular, the average condition of railway and road bridge structures has deteriorated significantly in recent years. The reasons for this can lie in an unexpectedly strong increase of the heavy-duty traffic during the past decades. This leads to an increased both static and fatigue loading and therefore to a considerable increase of fatigue damages in steel bridges in the form of cracks. Since, for economic reasons, the existing structures cannot easily be replaced by new constructions, the repair often is unavoidable. The application of carbon fibre reinforced plastics (CFRP) using epoxy-based adhesives shows high potential in order to increase the remaining service life of fatigue damaged steel structures. Compared to commonly used repair methods the cross-sectional weakening caused by bolted reinforcement plates as well as the notch effect and the negatively acting residual stresses caused by repair welding can be avoided. One of the main objectives of the current research project is the investigation of the influence of adhesively bonded prestressed CFRP lamellas on the reduction of the stress intensity at the crack tip and therefore an increase in the remaining lifetime of steel components. This paper focuses on experimental investigations on single-sided reinforced centre-notched specimens considering different adhesives, prestressing grades as well as loading conditions. In the first test phase of the fatigue testing for each specimen a 40 mm long crack is induced, which in the second phase is reinforced using adhesively bonded CFRP lamellas. In the third test phase the reinforced specimen is subjected to a fatigue test and the crack propagation is measured using RDS propagation gauges. The experimental results show a high potential for repairing fatigue damaged steel structures by the use of adhesively bonded CFRP lamellas. A significant increase of the remaining lifetime of the specimens can be observed. These results give good reason to further investigate the method of strengthening fatigue damaged steel structures using adhesively bonded CFRP lamellas.
