Bridges

The economic vitality of Auckland depends upon the movement of people and freight around the city’s motorways and the Auckland Harbour Bridge (AHB) is a crucial component of the network. Traffic loads derived from weigh-in-motion (WIM) data measured on State Highway 1 were found to have increased 50% since the last extension bridge assessment and upgrade in the 1980’s. The bridge was found not to satisfy current standards and so to support the regional economic growth strategy major intervention was needed to upgrade the structure for current and future demands. The addition of extension bridges to the original truss bridge was an innovative achievement in 1969 increasing highway capacity from 4 to 8 lanes. Getting the most out of the existing steel orthotropic box girder structure to extend the service life of the crossing was the key challenge for this project. Strengthening work was completed in 2010 using innovative techniques to deliver the required construction quality and fatigue endurance. More has been gained out of the AHB box girders than ever anticipated and the landmark bridge has been preserved for decades to come.