Smooth sailing for Melbourne’s newest skyscraper

Melbourne’s newest super-tall residential building isn’t just a prominent addition to the city’s soaring skyline, it’s one that will define it for decades to come.

At 289m tall and sitting 88 storeys above street level, the Aurora Melbourne Central building on Latrobe Street has earned itself the mantle of tallest building in the CBD and the tallest residential building in Melbourne. Only the Eureka building and the Australia 108 building (currently under construction) will surpass Aurora Melbourne Central for height, but both are in Melbourne’s Southbank.

Alexei Simm, Project Director for managing contractor Probuild, says the building has been specifically designed to offer seamless connections with the city below.

“The building abuts and connects with Melbourne Central railway station, so its unique offering is that it allows apartment occupants the chance to get in their secure lift, go down to the retail zone airlock in the basement, grab a latte and access the station,” Alexei says. “They can even stay within the central CBD shopping precinct and go as far as the Bourke Street Mall while staying undercover.”

The developmement, which is now structurally complete and about to be handed to owner UEM Sunrise Berhad in full, contains 1211 apartments and rooms. Of that total, 252 form part of a self-contained hotel operation, plus there are office and retail spaces at lower levels.

Reinforcing steel in construction

Structural engineers WSP Structures designed Aurora Melbourne Central as a reinforced concrete structure utilising an outrigger system with a stabilised central core and perimeter columns. These perimeter columns have been arranged so as to maximise apartment layout flexibility while also allowing the outrigger system to help resist lateral loads on the building’s core.

Alexei explains that mega-columns have been used, so-called because they can withstand loads additional to their own weight.

“A normal column will just transfer the weight of the building above it down to ground,” he says. “A mega-column restrains the added force of the building leaning on the outriggers.

“It’s a way of producing a very spatially efficient design for very tall buildings because it enables the central core – with the use of good-quality, high-quality reinforcing steel – to be slimmer and stronger than it would be in buildings not using an outrigger system.”

By sourcing steel through InfraBuild Construction Solutions (formerly LIBERTY OneSteel Reinforcing), Probuild was not only able to reactivate trusted relationships, but leverage steel’s inherent advantages to attain ambitious sustainability goals for the project.

“We decided to go with InfraBuild because of its local Australian base and the energy efficiency and low embodied energy of the recycled steel produced at its local mill. And also because of the long-term industry relationships we have with key personnel within the business,” Alexei says.

“When we started, we inherited a design that was about 20 per cent complete so that meant we had to complete the design while starting construction simultaneously. We identified early on that we wanted to activate all our best relationships in the industry to help us to come through that because it takes time to learn how to work best with people. If you already work best with certain people, you’re up to speed quicker. That was our experience with InfraBuild.”

Marc James, Probuild Assistant Project Manager says having access to a domestic supply of reinforcement gave Probuild the confidence that applicable AS standards and relevant code compliance were being achieved and adhered to.

The relationship between the two companies extended to InfraBuild embedding a dedicated production scheduler in the Probuild site office to fast-track workflows.

“It’s always difficulty scheduling steel reinforcement for a large tower,” explains InfraBuild Construction Solutions’ Sammy Mehtonen, who spent 18 months reviewing, querying and scheduling reinforcing steel deliveries for the project, “but it’s enormously easier if you’re face to face with the people making the decisions.”

Ensuring delivery of the right reinforcement at the right time was critical to the success of Probuild’s 4-day slab pour cycle.

“Impressively, there were no known issues recorded or identified with the quality of reinforcement,” says Marc James, “and none that prevented critical path works from occurring.”

Sustainability the aim

When the design for Aurora Melbourne Central went through the town planning stage in 2013, the project team had a mandate to apply the City of Melbourne’s Eco-City goals. These requirements were primarily focused on energy emissions (greenhouse gas), water consumption and waste reduction, but the team had no empirical standards in the Eco-City goals to apply the building’s performance against.

“We looked at them and thought ‘that’s potentially not enough’,” Alexei explains. We thought to ourselves, ‘there are a lot of good innovations going into this building, so we really should press it more’.”

When Probuild were engaged on the project, the company adopted relevant parts of the Green Star tool to enable it to develop better solutions for the nascent building – and be able to rate their effectiveness.

Probuild elected to work towards an overall 4 Star Green Star design and adopted elements of the GBCA residential assessment tool to guide the process. A total of 49 points were assessed as available and were targeted, including one point in the Mat-5 Steel (reinforcing) category, which promotes environmentally responsible production.

“We’ve aimed for as many of the requirements of Green Star as possible – and we’ve achieved most of them,” Alexei says.

As for the advantages inherent in using an advanced outrigger design, Alexei says it makes full use of the advantageous properties of steel. “Concrete without reinforcing steel is no good for strength, bending and deflection, and by using steel you end up using less concrete, which is a good thing because of the embodied energy in cement.”

He adds that a completed assessment of the overall built project is underway, but yet to be completed.

Building design

Architecture firm Ellenberg Fraser conceived the design of Aurora Melbourne Central design as having three elements. The first is a podium with a footprint of approximately 3650sqm. The building then steps back into a tower section and then two-thirds up, the design changes again. The building has lifts and lift cores dedicated to each of those thirds.

As is customary with very tall buildings, once levels have had their concrete slabs poured and been declared defect-free, they are passed to the developer so they have an opportunity to stage early handovers.

The first third of the building’s apartments were handed over and occupied from September of last year, with occupation of the next third having started in May. With the building now about to be handed over in full, there are currently about 700 occupied apartments in the building, as well as the hotel preparing for trade.

“One of our proud claims is that we’ve come up with a virtually seamless separation of occupants from construction activity,” Alexei says. “Not one resident complained about overt construction noise – and some of what we do is very loud.”

Working on a confined CBD site, the project team also had to adopt extremely lean and efficient processes when it came to scheduling, production and dispatch of materials from InfraBuild Construction Solutions’ Noble Park branch to the onsite team.

Alexei says the Aurora Melbourne Central project has employed some industry-leading technologies and created some best-ever efficiencies in construction. He adds that there has also been a significant amount of mentoring provided and career development for many of the individuals involved in the project.

“We’re exceptionally proud of what is not only an iconic building on the Melbourne skyline, but something that will be looked back on fondly as being a significant career milestone for many.”