Model-based durability design of concrete structures in Hong Kong–Zhuhai–Macau sea link project

• HZM model is established for durability design of chloride ingress.
• Fully probabilistic design is performed for different reliability levels and lives.
• Partial factor format design is set up from fully probabilistic approach.
• Design by partial factors gives conservative results by tolerance assumption.

This paper presents the durability design of concrete structures in the Hong Kong–Zhuhai–Macau (HZM) sea link project for a design service life of 120 years. Among all the durability issues, this paper focuses on the model-based durability design of concrete structures in the project subject to the action of marine chlorides. The mechanism and modeling of chloride penetration into concrete are reviewed in depth and the applicability of models for durability design is evaluated. On the basis of long-term exposure tests and in-place structural investigations during the past 30 years in South-eastern China, the design model for concrete structures in the HZM project is established. The statistical properties of model parameters are analyzed in details and compared to other chloride ingress models. Using the established HZM model for chloride ingress and specified durability limit state (DLS), the design parameters are first evaluated through a fully probabilistic analysis in terms of service lives (50 years, 120 years) and target reliability levels (β = 1.3, 1.5, 1.8). The partial factor format for durability design is then established and the partial factors are calibrated from the first order reliability method (FORM) from specified service life and specified reliability level. The design results from the partial factor design equation are given for different exposure zones, and the achieved reliability index is verified for each design through the full probabilistic method. Finally remarks are given on the HZM model and its application in durability design of RC elements.

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