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LIGHTWEIGHT STRUCTURAL STEEL PUTS FIVE-STOREY MULTI-RES PROJECT ON CARPARK

BlueScope structural steel has enabled the developers of a Brisbane project - the multi-stage Portside Wharf development - to overcome a potential design constraint and capitalise on an opportunity to increase yield, while also significantly reducing construction time and cost.

Brookfield Residential Properties (BRP) was keen to take advantage of an opportunity to redevelop a site six kilometres from Brisbane's CBD that arose from the relocation of the Brisbane Cruise Terminal, and pursued a development application for apartments and retail shops.

BRP regional director Lee Butterworth said the company faced a design constraint in the limited load-bearing capacity of the existing piled foundations of the car park on which they planned to build.

"The structural elements of the car park were designed for supporting heavy vehicles," said Mr Butterworth. "An analysis of the capacity of the existing piled foundations by structural engineers Bornhorst+Ward revealed two options: a three-storey concrete-framed building or a five-storey steel-framed building. The opportunity to yield another 16 apartments improved the viability of the project," he said.

Bornhorst+Ward senior structural engineer Paul Kelly made the unconventional recommendation to use a steel structure. He said steel was specified to keep the building structure light and allow for the development to maximise yield without requiring the demolition of the existing car park. "It would not have been feasible with any other material from the point of view of waste, span sizes, fire regulations and the BCA," said Mr Kelly.

TVS Architects director Maurice Verna was tasked with addressing the limited load-bearing capacity of the piers in the existing column-grid car park. "We had to find a lightweight building solution that would put 32 apartments and 500-600 square metres of retail space on the ground floor. The construction phase of the project clearly illustrated the benefits of a steel structure," Mr Verna said.

"The biggest benefit is in the speed of erection. While it took us a bit of time to gear-up for the project and construction stage, and there was a lot of time involved in detailing the structure, the five storey building was erected in about six weeks.

"The materials for construction were all in a kit, and all of the parts were labelled. It's a good system to adopt," he said.

Mr Butterworth agreed. "It was more cost-effective than other alternatives for this project and has been a lot less disruptive as we avoided going through demolishing procedures in a densely populated area."

The cost of the project - relative to the cost of demolishing the existing basement, installing new piles and building with a concrete structure - was reduced by an estimated 20 per cent.

Around 21 tonnes of BlueScope GALVASPAN® steel was used for purlins in the building's structure.

With a hi-tensile steel core, cold-formed galvanised purlins made from GALVASPAN® steel have a greater strength-to-weight ratio than traditional hot-rolled steel, reducing overall weight. The lighter sections also reduce fixing times, with self-drilling or self-tapping screws able to be used.

"The GALVASPAN® was easy to work with," said Steve Marais, director of the development's builder, Condev Constructions. "A lot of the ease with which it worked came partly from the product itself, and partly from the level of familiarity that the industry has with BlueScope products."

XLERPLATE® steel was used for the welded beams in the building. The roofing is made from COLORBOND® steel in Stratco's Topdek® 700 profile in the colour Surfmist®.

Three-and-a-half tonnes of DECKFORM® steel in LYSAGHT BONDEK® profile was specified for decking in flooring and balconies. "DECKFORM® was the only element with concrete on it; it just seemed to fit the model and the purpose. It was completely appropriate and was not a difficult decision to make," Mr Marais said.

Building with a steel structure also avoided disruption to the burgeoning retail and residential precinct. "We found it to be a very clean process," said Mr Marais. "We certainly benefitted from the lack of residual material traditionally left over from 'wet trades' such as surplus concrete, block fill and reinforcing off-cuts.

"We've been surprised at how clean and efficient it was working with steel products and how easily finishing trades follow the structure without requiring excessive clean-up afterwards. That's been time and cost-efficient for us.

"Concrete just wasn't a viable commercial option for this project," Mr Marais said. "I have had a bit of a mind-shift in regard to working with steel. I was typically cautious, as anyone would be, when doing something for the first time.

"Would I use steel next time? Without a doubt."

...ends/71553-0237



 
IMAGES
The BRP team against a background of welded beams made from XLERPLATE® steel.
Using structural steel, rather than demolishing and re-building using concrete, reduced construction costs by 20 per cent and yielded 16 more apartments.
Speed of erection was a key benefit. A six-week construction phase minimised disruption in the densely populated area.
Speed of erection was a key benefit. A six-week construction phase minimised disruption in the densely populated area.