Reliability-based determination of allowable corrosion degree to define the end of lifetime of concrete elements in bending

The assessment of reinforcement corrosion of a concrete structure is challenging due to all the uncertainties regarding the corrosion process itself and subsequent effects on the structural capacity. In this work, a proxy criterium for the determination of a structural capacity-based end of lifetime is proposed, expressed as the allowable corrosion degree. This value can be compared with the predicted corrosion degree over time to detect the time instant where structural interventions are needed. The criterium is based on the allowable level of corrosion by lowering the target reliability level for a structure from the design to the assessment phase. The advantage of this criterium is that it can be used to have a prior assessment of the need for a maintenance strategy in absence of more detailed investigations by either predicting the corrosion degree over time or by determining the corrosion degree in situ. It is shown that the critical corrosion degree mainly depends on the type of variable loading and the load ratio describing the ratio of variable over total loading. Moreover, the critical corrosion degree is significantly lower for structures subjected to traffic loads compared to other load cases such as wind, snow or other imposed loads.