Design for durability including initiation and propagation period based on the fuzzy set theory

Corrosion of reinforced concrete structures occurs in two stages characterized by different intensities of the corrosion development: the initiation period of the corrosion process and the propagation period of the corrosion process. Consequences of the reinforcement corrosion in concrete are the reduction of the cross‐sectional area of the reinforcement bars, and cracking of the concrete cover. The reduction of the reinforcement structural capacity due to the corrosion, over a sufficiently long period of time, may result in structural failure of the designed structural element. It is impossible to quantitatively express all corrosion factors influencing loss of the reinforcement structural capacity. Their influences on the structural design could be considered through a factor of safety applicable to the corrosion limit state. Factor of safety is calculated considering fuzzy sets theory and qualitative inputs of various influencing factors.