The unexplored potential of recycled skyscrapers
The Greenland Centre, Sydney, Australia
Since the 19th century, the reliability and versatility of steel has made it indispensable to high-rise construction projects all over the world, but what happens when those towers fall into disuse? A new project in Australia is shining a light on how steel can be used sustainably for future constructions.
In the heart of Sydney’s central business district, the former heritage site that once housed the city’s Water Board office is undergoing a massive refurbishment. The original building’s façade and interior have been fully demolished, but the exposed rigid steel frame is being put to use as the basis for a new build, which will see an additional 44 levels added to the original structure. Once completed, The Greenland Centre will become Sydney’s highest residential building, reaching a new height of 235 metres.
- Client: Greenland Group
- Architect: BVN
- Permanent works structural engineer: Arup
- Temporary works engineer: Robert Bird Group (RBG)
- Contractor: Probuild
- Structural steel: BHP (original supplier)
The project is being brought to life by the Shanghai government-owned Greenland Group in collaboration with Probuild, one of Australia’s largest construction companies. The architecture firm BVN was selected from a field of six international architects to design the tower through a City of Sydney Design Excellence Competition.
The goal is to create 470 apartments and six penthouses across 66 floors, while the adjoining art-deco building will also be converted to make space for a creative hub, street-level retail space and a boutique hotel.
How steel is contributing to a sustainable build
Construction on the $400 million refurbishment began in early 2015 and every effort has been made to ensure that the project is in line with the most sustainable construction practices. In total, 99% of all construction waste materials have been recycled, including 25,000 tonnes of concrete and 3,200 tonnes of brick.
This commitment to sustainable construction has also seen the majority of the building’s original steelwork retained. While the original concrete encasement had to be removed during the renovation, the original steelwork remains the backbone of the new building. The steel used for the original tower columns and both primary and secondary floor beams has been retained, with battened steel plates used to further strengthen the existing tower.
“The use of the existing steel frame pays tribute to Sydney’s architectural past, while the ‘Sydney Balconies’ provide an insight into Sydney’s future city living.”Simon Gray, Probuild Group Managing Director
The challenge of building on an existing structure
One of the greatest challenges for the Greenland Centre project is that the original building had only 26 floors. Highlighting the enduring strength and adaptability of the material, the tower’s original steel frame is being used to support the additional 44 levels that are being built on top of the existing structure. Successful completion relies to a significant degree on the strength and durability of the original steel construction.
The building’s original lateral system was constructed of vertical chevron bracing consisting of two steel plates in tension and compression. This vertical bracing stops at ground floor where lateral loads are transferred through ground floor to basement walls. Elsewhere, the building’s existing floor framing was developed with fabricated steel columns encased in concrete for fire protection, alongside precast ‘double T’ units spanning onto steel beams, and 22 metre clear spanning floor beams running through the centre of the structure.
Allowing for flexible, adaptable construction
The adaptability and flexibility of steel-based construction is enabling the construction team to overcome the challenges associated with adding new height to the tower, while also allowing for the design changes necessary to transform a former office into a premium living space.
The building will be encased in a modulating angled glass façade, which ensures that outdoor balconies are useable regardless of windspeed, while also providing additional support to the structure. In addition, the construction team is working carefully to ensure that building codes for residential properties were adhered to, without compromising on aesthetic design.
Paying tribute to Sydney’s steel architecture tradition
The original Water Board building incorporated cutting-edge construction techniques for the era, which were only possible thanks to the unique properties of steel and innovative thinking on the part of the original steel supplier, BHP. To provide column free office space – unusual for its time – double T beams were designed to span 7m between high-tensile steel beams spanning 25m. This new technique allowed for two floor panels to be erected at a time, allowing an entire floor to be laid in one day.
The ability to weld onto existing steel made it not only an ideal material to use, but allowed contractors working on the build to reflect on the central role steel has played in the development of the city’s skyline. Simon Gray, Probuild’s group managing director, said: “The use of the existing steel frame pays tribute to Sydney’s architectural past, while the ‘Sydney Balconies’ provide an insight into Sydney’s future city living.”
The rejuvenation of landmark towers such as the Greenland Centre wouldn’t be possible without the durability and reliability of steel. The skylines of the 21st century will need to be more sustainable than ever before and steel still has a crucial role to play.
As yesterday’s skyscrapers continue to be repurposed for modern needs, many of the materials they’re made of will need to be recycled, but steel will continue to serve as their backbone.
Images: BVN Donovan Hill via CTBUH, iStock