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Jul 08 Building an icon

ising 319 metres on Melbourne’s skyline, Australia 108 goes where no building has ever gone in the Southern Hemisphere.

It not only boasts the highest floorplate in half of the world, but also Australia’s first cantilevering structure – the golden Starburst that juts out over the street across all four sides of the building.

So just how was this architectural phenomenon delivered?

Builder Multiplex started work on Australia 108’s compact and challenging site in late 2015. Located in the heavily developed suburb of Southbank, the site is bounded by neighbouring tall buildings and two major roads. Its location was never going to make construction easy.

Nor would its soil. Australia 108 is located on Coode Island Silt – like the majority of buildings in the area – a highly compressible soil. To shore up the integrity of the structure Multiplex spent the first 12 months founding over 250 piles into the ground.

Using the biggest piling rig in Australia, some of the piles were up to 2.1 metres in diameter and were founded up to 47 metres deep into the bedrock of the site. This scale of piling gave the building a strong foundation from which its 100 storeys could begin to sprout.

Once piling was complete, the building started to come out of the ground, with new floor slabs poured at monthly and even fortnightly intervals on higher levels. This progress allowed for progressive façade installation – a feat in itself. Australia 108 features 15,000 unique glass panels weighing between 200-300 kilograms (that’s a massive 2,500 tonnes of glass spanning 47,000 square metres).

As the glass was installed, trades were able to begin working on apartment interiors, with a buffer of up to 20 levels between these workers and those pouring concrete as the building’s form rose.

Undoubtedly one of the largest challenges on the project came with the construction of the building’s now iconic Starburst. Located 210 metres above ground over levels 70 and 71, this golden feature juts over the street below. It comprises 24 trusses weighing 12 tonnes each and spanning 15 metres by 3.3 metres with similarly sized golden panels.

Multiplex erected a special platform under the Starburst from which workers could safely install the feature, while ensuring the safety of people below. It took more than four months to complete, with the golden panels lifted in place at night as to not disrupt the traffic below.

The building was designed so that the upper levels could proceed as the Starburst was finished and to ensure that any delays on the feature would not impact the delivery of the remainder of the structure.

This structure on its upper levels is further stabilised by a series of outrigger walls and there are a range of interventions to help it cope with the gale force winds that can blow off Port Phillip Bay. One of its key wind management features is a 300,000 litre damper tank installed below level 100 to act as a counterbalance against wind and help the building flex.

At times these gusts did slow construction, with the weather the biggest uncontrollable factor on the site. Despite the challenges that the external conditions provided, the build of this icon has proceeded to plan and on schedule.

In April Australia 108 marked its topping out moment, with the majority of its glass façade in place, signalling completion of the structure. Its two cranes that have dominated the skyline for so long will start to come down as trades move inwards to focus on completion of the remaining internal spaces and apartments – on track for completion by the end of the year.