Brookfield Residential Properties (BRP) used BlueScope structural steel to redevelop an existing site in Brisbane, overcoming a potential design constraint.
BRP, the developers of the multi-stage Portside Wharf development, had an opportunity to redevelop the site located six kilometres from Brisbane's CBD that arose from the relocation of the Brisbane Cruise Terminal.
Pursuing a development application for apartments and retail shops, the developers 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.
BRP regional director Lee Butterworth explained that the structural elements of the car park were designed for supporting heavy vehicles. An analysis of the capacity of the existing piled foundations of the car park by structural engineers Bornhorst+Ward revealed the possibility of a three-storey concrete-framed building or a five-storey steel-framed building. The opportunity to yield an additional 16 apartments improved the viability of the project, encouraging BRP to choose the five-storey option.
Bornhorst+Ward senior structural engineer Paul Kelly made the unconventional recommendation to use a steel structure. The steel frame solution was specified to keep the building structure light and allow for the development to maximise yield without requiring demolition of the existing car park.
According to Mr Kelly, it would not have been feasible with any other material from the point of view of waste, span sizes, fire regulations and the BCA.
TVS Architects director Maurice Verna was tasked with addressing the limited load-bearing capacity of the piers in the existing column-grid car park. Mr Verna said they 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 biggest benefit of the steel-framed structure came from the speed of erection. Though the project took some time to get off the ground while preparatory works were being undertaken in terms of detailing the structure, the five-storey building was erected in about six weeks.
Mr Verna said that the materials for construction were supplied in a kit, and all the parts were labelled.
BRP’s Mr Butterworth said that it was more cost-effective than other alternatives for this project. He added that it was also a lot less disruptive as they could avoid demolition procedures in a densely populated area.
Since the steel-framed structure eliminated the need to demolish the existing basement, install new piles and build with a concrete structure, the developers were able to reduce costs by an estimated 20 per cent.
Around 21 tonnes of BlueScope GALVASPAN steel were used for purlins in the building's structure. Featuring 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 also used.
Steve Marais, director of the development's builder, Condev Constructions observed that GALVASPAN steel was easy to work with; he attributed this ease of use to the product itself, as well as the level of familiarity that the industry has with BlueScope products.
BlueScope steel products used in the project also included XLERPLATE steel for the welded beams in the building, COLORBOND steel in Stratco's Topdek 700 profile and Surfmist colour for the roofing, and 3½ tonnes of DECKFORM steel in LYSAGHT BONDEK profile for decking in flooring and balcony areas. DECKFORM was the only element with concrete on it.
Building with a steel structure also avoided disruption to the burgeoning retail and residential precinct. According to Mr Marais, they benefitted from the lack of residual material traditionally left over from 'wet trades' such as surplus concrete, block fill and reinforcing off-cuts. The entire process was clean and efficient with finishing trades able to complete their work without requiring excessive clean-up afterwards.