Bridges

The exponential rise of the population and freight load in Victoria have led to a strong need for the upgrade of existing infrastructure to accommodate the increase in demand and loads of high productivity heavy vehicles. In many instances, upgrading Victoria’s infrastructure entails widening and/or strengthening existing roads and bridges to meet demand and the latest design standards. This paper reports the design and constructability challenges and outcomes of upgrade works applied to a number of existing bridges along the Tullamarine Freeway. The City-Tullamarine Widening (CTW) (Section 2) project involves strengthening bridge structures that were built in the 1960s-70s to withstand the client-specified requirement of 75% SM1600 truck loading. To meet these requirements, different structural elements required attention, including abutment and pier crosshead strengthening, girder strengthening, and deck strengthening to allow for on-structure barrier upgrades. Techniques proposed to strengthen these elements include the use of carbon fibre strengthening (rod & laminate) on crossheads, external posttensioning and concrete web thickening on pre-stressed I-girders, the use of steel plates on steel I-girders, and the use of -anchored dowels to connect elements to act as composite sections. These are in addition to incorporating strengthening girders for increased deck capacities to accommodate barrier upgrades. The design of these strengthening works created many challenges, such as determining solutions to ensure minimal traffic disruption, allowing for ease of constructability, ensuring safety during construction, and determining the most viable and economical solutions. Therefore, the designs incorporated strengthening methods that provided specific unique details and careful construction staging methodology to ensure these requirements were met.