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The construction of the Epping-Chatswood rail line provides a cross-link in urban transport infrastructure of Sydney, Australia. Isolating the vibrations caused by trains was the main challenge faced by the designers of a new interchange. | ||||||||||
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This multi-faceted engineering and building project involves the design and construction of both a temporary and a new railway station comprising twin island platforms and commuter concourse, bridgeworks, new bus interchange, taxi ranks, kiss-and-ride facilities, basement car park, 10,000 m2 of convenience- based retail, and rail track work to accommodate the new Epping to Chatswood line. The project also includes provision for the future construction of three residential towers over the interchange. "The main issues for the design team were isolating the vibration caused by the trains and separating this vibration from the residential towers (to be built in the final stage) - and that’s where we’ve used the Trelleborg floating slab bearings, to prevent any reverberation travelling through adjoining structures," says Laing O’Rourke project engineer Chris Paras. "As the basement car park had to be built underneath the existing station, we had to move the station while we built half the basement and then move it back to complete the rest," says Paras. This is the first time floating slab bearings have been used in heavy rail in Australia. Paras and his team had previously used isolation base plates (called Cologne Eggs) on fixed track slab at Bondi Junction train station, but the floating slab track created a new challenge. Finding the best way to isolate the main slab - which supports the track, station, shopping centre and the three towers - was imperative. "Trelleborg bearings have a good reputation in the rail industry generally and had some history with Railcorp, the NSW railways operator," says Paras. The Trelleborg product has demonstrated that it met their stringent requirements, including a life expectancy of 50 years. The Laing O’Rourke team travelled to Hong Kong to see the bearing pads in a similar railway application and then based their needs on the product’s performance in Hong Kong.
Shaun Jones, senior estimator with Trelleborg Engineered Systems Australia says the main challenge was to develop a floating slab track solution that conformed to the client’s requirements. "We have a long history of manufacturing rubber bearings for these applications, we were able to draw on our experiences and, combined with research and development, were able to offer a solution that met the client specifications," he says. Trelleborg offered the client three types of floating track bearings- support, end and side bearings. The manufacturing of these bearings was shared between two units within Trelleborg Engineered Systems, Trelleborg Queensland Rubber and Trelleborg Hercules (Singapore). Both facilities are ISO 9001:2000 certified. "To substantiate the performance requirements of the bearings, static load tests on the bearings were conducted in our certified laboratory in Brisbane. Dynamic Stiffness tests on the bearing were conducted on our behalf by James Cook University in Townsville," says Jones. "Having an ISO/IEC 17025 (1999) certified laboratory at our Brisbane manufacturing site is critical to our business as it allows us to provide our customer a complete package: Design, manufacture, testing and delivery. We have learnt to be flexible in relation to our customer’s demands. Our global presence is a major advantage," Jones concludes. Floating Slab Tracks (FSTs) are a mass-spring system for achieving a high levels of vibration isolation. FST bearings are suitable for reducing low-frequency ground-borne vibrations. The rail track floats on this rubber bearing system. They are used in close proximity to noise-sensitive structures such as performance halls, residences, schools and office buildings. | ||||||||||
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"The main bearings were bonded on the underside of the pre-cast slab sections and the lateral bearings then had to be inserted on the long side. Side bearings had to be compressed for installation and the tolerances were only plus or minus one millimeter either side,"says Paras. "We came up with a system that made it relatively easy to install them despite the tight tolerances. Our rail
crews saw this as a good opportunity to learn some new skills and did not baulk at the challenge. Although the first 400 meters floating slab track they installed took two weeks, the second
one took only a week."
Copyright © 2007 Thomas Publishing Company