Analytical and Experimental Service Life Assessment of Ningbo-Zhoushan Port Main Channel Sea Link Project

Abstract

The Ningbo-Zhoushan Port Main Channel (NZPMC) sea link is one of the most important projects undertaken by the People's Republic of China. The main factors that determine the service life of these marine structures, exposed to chloride-induced corrosion, are the "penetrability" and thickness of the concrete cover that protects the steel reinforcement. In an initial design phase, these factors are defined by modeling the penetration of chlorides with analytical tools (based on the Duracrete approach). In the construction phase, data are collected from the in-site laboratory for concrete chloride diffusivity, and from non-destructive tests for the concrete cover thickness and air permeability for the prefabricated bridge piers. On the basis of these data, two model-based approaches are used to predict the service life of the bridge. The first model is an analytical one based on the solution of Fick’s 2nd diffusion law, for chloride ingress into concrete using the corrosion initiation as durability limit state.The second model uses the “Exp-Ref” model, using the concrete cover thickness and air permeability as input parameters and calibrated by the EuroCode specifications on structural concretes in marine environments. Both approaches use Monte-Carlo simulations and consider the statistical properties of the input parameters. A comparison of the analytical and experimental predictions is made, showing compatibility with 100 years of service life. The convenience of verifying the analytical predictions with those obtained from site experimental data is discussed.

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