Surface deterioration analysis for probabilistic durability design of RC structures in marine environment

In probabilistic durability design of concrete structures in marine environment, the limit state is defined as the corrosion initiation of reinforced steel. However, the owner may more concern the cracking growth of concrete surface or the first repair time without maintenance, in that case, additional information on surface deterioration should be supplemented to eliminate owner's concern. This paper employs the two-dimensional simulation method to predict the surface deterioration process for reinforced concrete structures exposed to aggressive chloride environment. The spatial variability of concrete cover (c), chloride diffusion coefficient (Da0) and other durability parameters are considered in the simulation, and the effect of batch-production of concrete is accounted for in the spatial variation modelling of c and Da0. Taking the Hong Kong-Zhuhai-Macau sea-link project as an example, the paper evaluates the durability performance of the immerged tube tunnel over the expected service life, and compares a range of durability design specifications with different target reliabilities and combinations of c and Da0, in terms of the probability & extent of surface damage. With three maintenance levels prescribed by surface damage grade at intervention, the paper compares the intervention time of different durability design specifications. The results provide a comparative tool to aid designers in selecting design specifications to achieve owner-concerned durability objective.