Extent of spatially variable corrosion damage as an indicator of strength and time-dependent reliability of RC beams

A spatial time-dependent reliability model is developed for a RC beam subject to corrosion-induced pitting corrosion. The analysis considers the spatial and time-dependent variability of pitting corrosion and its effect on cover cracking and shear and flexural resistance. The model uses extreme value theory to predict maximum pit depth as a function of bar diameter and reinforcing bar length. The effect of corrosion on the mechanical behaviour of reinforcement and associated loss of ductility is also considered. A 1D spatial model is included where concrete properties, concrete cover and the surface chloride concentration are treated as random fields. The model is then used to predict the likelihood and extent of corrosion-induced cracking (corrosion damage). The spatial time-dependent reliability model allows the loss of structural capacity and reliability to be calculated conditional to the observed extent of corrosion damage. This allows the interaction between corrosion damage and loss of structural safety to be inferred for a deteriorating RC beam. It was found that the crack width at time of structural collapse is often well in excess of 1 mm. It was also found that the extent and location of severe cover cracking is an important indicator of structural reliability.