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Concrete In Australia : September 2014
NEWS 12 Concrete in Australia Vol 40 No 3 For more information and to register go to http://www.concreteinstitute.com.au/Events/254.aspx. Platinum Sponsor Gold Sponsors CIA NSW Branch Mini Conference – Wednesday 17 September 2014 – Sydney This half day event will feature: PUSHING THE BOUNDARIES IN CONCRETE TECHNOLOGY • Keynote Address by Dr James Aldred (AECOM & UNSW) • Multiple Speaker presentations • Competition presentations for students and practising engineers under the age of 30 • Wrap up and discussion session by Dr Daksh Baweja (Engineered Material Solutions & UTS). Proudly supported by our event sponsors: The challenges of supertall buildings Allianz Global Corporate & Specialty has released a report on Supertall Buildings 2014 asking the question, how high in the sky can they go? With current technology, a realistic achievable height is 1.6km (one mile) although this is not expected for another 20-30 years. Significant technical issues involve the pumping and placing of concrete at extreme heights. Concrete mixes will need to vary to withstand differing buildings’ loads which vary with height. Global head of engineering risk consultants at AGCS, Ahmet Batmaz said, “it is very difficult to pump concrete at this height – the high- strength concrete requires a specialised mix design to enable it to be pumped and it requires special equipment and pump lines as pressure can reach over 400 bar. It also creates some technical challenges during the stage where the concrete is mixed and placed as such concrete tends to set after two hours only”. The record for the tallest building in the world is currently held by the Burj Khalifa in Dubai at 828m (2716ft), completed in 2010. By comparison, the original World Trade Center in New York was 417m (1368ft). The Burj’s structural system can be described as a “buttressed core” and consists of high performance concrete wall construction. This central core provides the torsional resistance of the structure. However, the UAE monolith will soon lose its place as the record holder as construction has already started on the Kingdom Tower in Saudi Arabia, which will be the first building ever to pass the 1km mark. This building is due for completion at the end of 2018 and will form the centrepiece of the 50ha Kingdom City waterfront development on the Red Sea in Jeddah. However, Allianz says beyond 1km, skyscrapers would most likely need to have two or three buildings interconnected with horizontal elements bracing the “legs”, meaning that single tower structures like the Kingdom Tower may be unfeasible at heights beyond 1km. As expected, it was not without its foundation and piling design challenges. The concrete had to have low permeability in order to resist the salt-laden ground water which is characteristic of the region. According to foundation contractors, Saudi Bauer, the work involved installing 72 piles of 110m in length and 1.5m in diameter; a further 154 piles of 1.5m in diameter and between 49 and 89m in length; and 44 piles with a diameter of 1.8m, all down to a depth of 50m. To limit excessive movement at height, very high strength concrete that will be up to several feet thick will be used in certain parts of the core. This, along with the highly integrated steel frame and shear walls, is also intended to prevent catastrophic structural failure. CIA 40-3 FINAL.indb 12 CIA 40-3 FINAL.indb 12 26/08/14 9:18 AM 26/08/14 9:18 AM