Reliable Assessments of Concrete Structures with Corroded Reinforcement: An Engineering Approach

Licentiatavhandling, 2017

When in service, concrete structures are inevitably exposed to detrimental processes which, over time, can affect the structures’ ability to fulfil their structural requirements. The most common cause of deterioration of concrete structures is corrosion of the reinforcement; a problem that is expected to become more severe in future, due to climate change. Nevertheless, the demands for load-bearing capacity often increase with time. Advances in engineering methods are needed for reliable structural assessment of existing structures. Such methods should be calibrated with experiments and advanced analyses and complemented with approprate safety formats. This will allow us to meet future needs in an environmentally friendly and economic way and avoid unnecessary re-constructions. The influence of load history on reliability level was compared for the safety formats provided in fib Model Code 2010. A statically indeterminate structure subject to vertical as well as horizontal loading was analysed. Not all safety formats reached the intended safety levels for all load histories. This illustrates how important it is to consider the load history when making structural assessments. One stage in developing an engineering model for bond of corroded reinforcement was to investigate the possibility of using thin-section models to represent bond behaviour in beam anchorage zones. Thin-section models were compared to larger, finite element models as well as experimental results. The results showed that the thin-section models may be able to capture the bond capacity, although the results were strongly influenced by the boundary conditions applied to the thin-section model. An existing one-dimensional model was further developed showing the bond capacity of corroded reinforcement bars in concrete. This new model was based on the local bond stress-slip relationship in fib Model Code 2010 and was calibrated against a large database of bond test results. During the verification, the model showed results which were slightly on the safe side. There was also good agreement with an empirical expression for bond capacity found in the literature. The contributions made by this work provide engineers with a simple, verified model of the bond capacity of corroded reinforcement in concrete. They also facilitate the development of a more holistic and reliable assessment method. The knowledge gained about the influence of load history and boundary conditions will be utilised in further development of the one-dimensional bond model, as it will be expanded to cover more reinforcement layouts and complemented with an appropriate safety format.