Bridges

This paper explores a cost-effective approach to maintenance and strengthening rehabilitation works of existing bridge assets subject to higher capacity tram fleets in Melbourne. Specifically, it examines the case for strengthening upgrades to the Raleigh Road bridge across the Maribyrnong River in Melbourne’s west, where recent and historical flood damage combined with tram fleet upgrades have created unique challenges in achieving a robust, reliable and economically viable solution using limited resources.

In response to customer and network need for higher capacity, more modern and more efficient tram operations, the Department of Transport and Planning (DTP) has progressively rolled out new tram rolling stock on the Melbourne network over the past 10 years. Tram routes typically run on existing road reserve, shared with road traffic, and utilise older bridges designed with lower live loading capacities than current standards would normally permit. Consequently, DTP must achieve a balance between strengthening and rehabilitation works to meet current standards at inflated cost, on one hand, and meeting expected serviceability requirements for the current and future tram fleet with a reasonable and reliable safety margin, on the other. The latter option can be achieved at much lower capital cost, with very low ongoing risk to the community.

This model study examines the most adverse loading combinations of current and future tram vehicles with road vehicles, given a suitable and reliable safety margin, to obtain the optimum serviceable solution for strengthening. The study also considers the remaining residual life of the structure, and the whole-of-life cost to retain a serviceable residual life, against the alternative options that include reconstruction and associated network disruptions.