The installation of the Auckland Harbour Bridge (AHB) Box Girder Extension Bridges (‘clip-ons’) took place in 1969, 10 years after the original Truss Bridge was constructed. Since then, traffic loading on this critical route has increased dramatically and will continue to do so into the future. In order to meet future traffic demands on the AHB, it was determined that the load carrying capacity of the extension bridges had to be increased in the form of the Box Girder Strengthening Project.
The scope and scale of the strengthening works was unprecedented for this type of bridge. Approximately 600,000 man hours were expended over the duration of the project and nine hundred tonnes of new steel was distributed along the full length of the bridge. This included:
The project brought many associated challenges including difficult access and logistics, work at height, confined space, ventilation issues, the delivery of approximately 10,000 individual components each weighing up to 500kg, strict road closure conditions and extremely tight design fit-up tolerances of less than 1mm for the components welded in high fatigue areas. The successful outcome of the project required innovative design work and construction methods, combined with a collaborative approach from not only project team members but also local residents, stakeholders and the road users.