Aging Effects on Interactions of Embedded and Externally Bonded Reinforcement in Strengthened Concrete Structures
Concrete constructions like bridges are an integral part of our transport infrastructures. In Germany, there are more than 39.000 bridges on the federal highways. More than half of those bridges have an average age of 40 – 50 years. Those reinforced concrete structures are often exposed to aging phenomena and environmental conditions. Externally bonded reinforcement (EBR) made of carbon fibre reinforced polymers (CFRP) are widely used for the strengthening of reinforced concrete components, due to its low weight and great mechanical characteristics. However, due to the different bond characteristics of EBR and steel rebar, the strain distribution deviates from the distribution determined presuming a plane strain distribution. Above that, limited works has been reported on the long-term behaviour of concrete members strengthened with FRP. With regard to structural health monitoring (SHM), a precise calculation model of the strain distribution of the different reinforcement types needs to be developed.
The aim of the research project is to determine the internal forces in concrete, steel and externally bonded reinforcement of a reinforced concrete component under sustained load. For this purpose, approaches have to be developed to determine the distribution of forces between embedded steel reinforcement and EBR under consideration of different bonding conditions.
Experimental investigations on strengthened reinforced concrete beams will serve as a basis for the modelling of the time-dependent load-bearing behaviour of different reinforcement strands as well as the degradation behaviour of the bond behaviour. Furthermore, state-of-the-art fibre optic measurement systems are used to record the strain distribution of the reinforced component over the period of investigation.
With the description of the time-dependent material behaviour and the degradation models of the load-bearing behaviour, it will be possible to create a prediction model that is able to calculate the residual load-bearing capacity of the reinforced structure.
Publications within the framework of the RTG
Conference contribution without publication in conference proceedings:
Z. Chen, H. Grefe, T. Leusmann, K. Dilger and D. Lowke. Quasi-continuous strain measurement with distributed fibre optic sensors in reinforcement bars and externally bonded CFRP strips at concrete slabs - Experiment and modelling. International Institute for FRP in Construction, FRPRCS-14, Belfast, June 2019.