Assessment and strengthening of a Melbourne toll-way viaduct

Yarra Bridge and Gardiners Creek viaduct together form a major elevated structure in the Melbourne CityLink toll-way: the busiest route in the Victorian freeway system. Originally constructed in the 1960s, they have been twice widened and modified extensively. The original structures recently required to be upgraded to withstand current and anticipated future loading. This paper discusses the viaduct's load rating by way of a combination of analytical assessment and observation of the structures' actual condition followed by the development of preferred strengthening concepts in conjunction with the contractor and asset owner. The methods used, including concrete infill, carbon-fibre strengthening and external post-tensioning, were designed to be flexible so they could be modified where ‘as-constructed’ details were found to differ from the original design drawings. Remedial works were also designed to be carried out below deck level, avoiding disruption to toll-way traffic while minimising the impact on stakeholders below.