Bridges

* Best Young Author Paper Winner Austroads Bridge Conference 2022

Monash Freeway spans across Jacksons Road and Police Road, originally as twin, three-span, highly skewed continuous I-beam bridges. These twin bridges were constructed in the 1970s with a wide gap in the median. Since then, they have been subsequently widened twice in the median and once on the verges. As part of the Monash Freeway Upgrade Stage 2 Project (MFU2), the existing bridges over Jacksons and Police Roads required widening in the median between these independent adjacent bridges to become a single monolithic superstructure. These bridge widenings were complex due to the different structural systems in the original and each of the historic bridge widenings. The effects of the bridge continuity together with the high skew was compounded by the articulation complexities, as the original bridges were supported on bearing pads whilst the subsequent widenings incorporated elastomeric and pot bearings. The various types of bearing and expansion joints significantly impacted the overall behaviour of the structure after widening. In addition, the bridge widenings were designed and subjected to different traffic loading, thermal effects, and experienced different aged effects of creep and shrinkage, which had a pronounced influence on the proposed median widening. The challenges of the complex bridge widenings were ensuring the new widening did not adversely affect the performance of the existing bridges, nor reduce their load carrying capacity. This paper will address how the history of previous widenings was considered in the various analytical stages, key issues such as: in-plane rotation of the deck, high skew, the varied articulation systems of the historic bridge widenings, and the resolution in the final design of the median widening to form a lessons learnt that can be adopted for future bridge widenings.