Durability Model Analysis Of Marine Concrete Structures Based On In-situ Test Data

The service life of reinforced concrete(RC)structures in marine environments is mainly influenced by the chloride-induced corrosion of reinforcement,and the development of chloride penetration model is essential for its assessment.The Fick's second law of diffusion provides a simple approach to predict the chloride penetration in engineering practice,and the apparent values of the parameters of this model are determined by fitting the measured data to the Fick's law.In this study,a large number of durability inspection and evaluation reports of high-pile wharfs located at the south coast,east coast and north coast of China are collected.Based on the long-term field results of real structures,durability model analyses of marine concrete structures are carried out on three aspects: geographical region,data source and vertical distribution.At the aspect of geographical region,durability inspection and evaluation reports of high-pile wharfs located at the south coast,east coast and north coast of China are screened,and the chloride profiles in these reports are fitted to the Fick's second law to obtain the statistical models of apparent surface chloride content and chloride diffusion coefficient of the three regions in splash zone.The comparison of statistical models shows that apparent surface chloride content of the three regions has little difference,but apparent chloride diffusion coefficient of south coast and east coast is significantly higher than that of north coast.This result can explain the phenomena that the chloride-induced corrosion of wharf members in the southern region of China is more serious than northern region.Apparent surface chloride content is observed to follow lognormal distribution according to its statistical histogram.Bayesian updating is performed for the mean value of surface chloride content in Chinese Code,and posterior distribution is derived.At the aspect of data source,the filed investigations of high-pile wharf structures located at the south coast of China are carried out,and the results are compared with the long-term exposure test results in terms of chloride ingress profile.The probability models and time-dependent models for surface chloride content and chloride diffusion coefficient are derived according to these results;and finally the effects of different models of chloride ingress parameters,based on exposure trails or based on real structure surveys,on the expected service life of marine structures are investigated.At the aspect of vertical distribution,the durability reports which contain chloride ingress profile and height of members in tide and splash zone are collected,and vertical distributions of surface chloride content and chloride diffusion coefficient are derived.Compared with the real structure surveys,it is found that the in-situ inspection results are in good agreement with the calculation results when considering the vertical distribution of durability parameters.Durabiltiy design is compared for two cases: considering or neglecting the vertical distribution of durability parameters.It is found that the designed cover thickness neglecting the vertical distribution of durability parameters can't satisfy the durability requirement for members in the middle part of tide and splash zone.