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Concrete In Australia : June 2013
Concrete in Australia Vol 39 No 2 55 3 operated the jacks. e aqueduct segments were launched using a strand cable system. A VSL pulling unit was attached to Pier 3 and with the trailing frame. e pulling end anchor with four VSL 6-7 strand bundles was fixed to the underside of the segments via a trailing frame. e trailing frame was fixed at the back of the segment using VSL CT stress bars, as shown in Figure 16. e segments were launched by pulling the strand bundle, which was moved through the jacks. e strands were pulled back through the jack at the change-over to next segment and the pulling anchor refixed to the pipe. e aqueduct was in its final position on completion of the fourth launch. e precast concrete trough sections were placed on each segment prior to launch in order to streamline the construction program. e internal HDPE liner was then welded to seal the entire internal surface and protect it from the aggressive environment that exists within the WTS. 8.0 CONSTRUCTION SEQUENCE AND INCREMENTAL LAUNCHING On average, it took 5-8 h to launch each segment. VSL was responsible for a number of key construction tasks on this project, including the strand launching system; launching nose; temporary structures for launching with skilled supervision and operators; load transfer from temporary launch to permanent bearings; and method engineering to assist in the incorporation of the VSL systems into the project scheme for incremental launched method (ILM). Launched from the east abutment, the aqueduct segments were pulled forward by hydraulic jacks. Low friction bearings on piers made it possible to slide the heavy superstructure forward. Located at the pier nearest to the casting bed, the strand jack system was designed to resist the longitudinal launching forces. A high degree of accuracy was required to ensure that the aqueduct was aligned correctly. Any unanticipated misalignment could have resulted in secondary and unaccounted stresses in the launched aqueduct. Accuracy was achieved by utilising lateral guide bearings fixed at each pier and launch bed rails, as shown in Figure 14. 9.0 CONCLUSION e design of the Werribee Aqueduct demonstrated that innovation and ingenuity, supported by a strong working relationship between designer, contractor and client can progressively solve challenges and achieve outstanding project outcomes. Sustainability of the project was enhanced by the use of an incremental launching construction approach. e approach allowed high durability of concrete segments for the superstructure to be constructed under controlled conditions. e use of an HDPE liner will further protect the concrete from the severe corrosive environment. e design achieved significantly less OHS and environmental issues, greater quality, lower cost and shorter construction time than an alternative design with a single span cast-insitu concrete structure. e alliance environment allowed teams to work seamlessly together to solve design and construction challenges progressively as part of the design process, while broader stakeholder issues were carefully identified and resolved. e artist s impression of the completed aqueduct is shown in Figure 17. REFERENCES 1. Standards Australia (2004). Australian Standard. Bridge Design, Standards Australia International, Sydney, AS5100. 2. Hambly, E.C., (1991). Bridge Deck Behaviour, Chapman & Hall. ACKNOWLEDGEMENT e authors wish to thank Pipelines Alliance for permission to publish this paper. e views expressed in this paper are those of the authors. Figure 16. Trailing frame to segment. Figure 17. Artist s impression of aqueduct.