Durability and Service Life Modelling for Cobham Bridge

BCRC’s Durability and Service Life Modelling

Understanding design life is essential in building sustainable, safe, and cost-effective structures. By carefully planning for and maintaining a structure’s design life, industries can achieve long-term savings, reduce environmental impact, and ensure safety for generations.

In 2022, BCRC Durability Consultants partnered with Fulton Hogan to extend the design life of the super tee beams on the Cobham Bridge, part of the project to build a section of the Hamilton Ring Road in New Zealand. The project aimed to extend the service life of the beams through a specialised protective coating.

This project highlights BCRC’s approach to durability and service life modelling to safeguard long-term resilience in bridge structures.

BCRC’s Design Life Assessment

During the design life assessment, BCRC evaluated the concrete cover across the Cobham Bridge beams. To meet the required design life of 100 years, BCRC recommended a high-performance coating system—Duralkote 700—that ensures protection against carbonation and environmental factors, which is critical for achieving the desired design life.

Solution for Enhanced Durability and Extended Design Life

Testing of the coating was conducted to verify its performance, which surpassed the minimum required specification by far.

Application Process and Quality Assurance in Service Life Modelling

To ensure durability and design life adherence, BCRC developed a rigorous Inspection and Test Plan (ITP) to monitor coating application quality. BCRC specialists went on-site to inspect the initial phase of the coating application and verify its adherence to the ITP.

The whole process was rigorously verified against the NZ standards and industry-accepted best practices.

 Achieving the 100-Year Design Life with Durability and Service Life Modelling

After extensive testing, BCRC’s approach to design life modelling on the Cobham Bridge demonstrated the Duralkote 700 coating’s ability to withstand carbonation. This, combined with the concrete’s protective properties, aligns with New Zealand Standard NZS 3101, ensuring corrosion resistance and supporting the projected 100-year design life.

BCRC’s durability and service life modelling strategies, combined with expert application and quality assurance, have fortified the Cobham Bridge’s super tee beams for long-term resilience. This project underscores the value of advanced design life assessment and maintenance in achieving robust, enduring infrastructures.