Auckland Harbour bridge traffic load assessment and strengthening

The Auckland Harbour Bridge was originally opened in 1959 as a four lane steel truss bridge with a 244m main span. In 1969, two lane extension bridge box girders were added on either side of the original truss bridge. The bridge design loadings were relatively low by modern standards. Demands on the facility have increased considerably since it was completed. The bridge is a critical link in Auckland's infrastructure, and Transit New Zealand, as owner and manager of the asset, recognises the need to maintain appropriate levels of serviceability and safety for the facility. In 1999 Transit initiated a programme of live load demand and capacity assessment. This commenced with the development of a Traffic Load Model for the AHB, using probabilistic assessment techniques. When this work was complete, live load capacity assessments of the truss bridge and extension bridges were commissioned. This paper outlines the development of the AHB Traffic Load Model and compares the outcomes with other international loading standards. It then describes the application of the load model to the assessment of the truss bridge and the assessment outcomes. Finally, the strengthening concepts and design developed to address the truss bridge deficiencies are outlined. (a) For the covering entry of this conference, please see ITRD abstract no. E214936.