ENGINEERING FOCUS: THE GREEN
THE CONSTRUCTION PROGRAM OF THE GREEN RESIDENTIAL PROJECT IN MELBOURNE WAS MARKEDLY REDUCED THROUGH THE USE OF PREFABRICATED CASSETTE FLOOR SYSTEM AND ENGINEERED WALLS. STRUCTURAL COLLEGE BOARD CHAIR KARLIE COLLIS INTRODUCES A PROJECT THAT RAISED THE BENCHMARK ON DESIGN AND DETAILING FOR ENGINEERING CONSULTANCY IRWINCONSULT.
The Green apartment complex, located in Parkville, Melbourne and developed by Fraser Property (formerly Australand) was the first of its kind Melbourne to adopt timber framing for a building of this height, using traditional timber framing stud wall and floor joist system.
Mark Paterson, Associate Director and Phil Gardiner, Managing Director – Irwinconsult, confirm the structure consisted of a concrete car park below podium level while above the podium, all five levels were constructed completely in timber.
“The timber frame superstructure was constructed using prefabricated timber walls, floors and roof trusses constructed off-site and delivered for installation. This was achieved by collaborating with the concept architects, SJB Architects and Australand, to configure an efficient grid system and load transfer through the stacking of apartments early in the program.”
The prefabricated floor system was a product of collaboration between Irwinconsult and Australand to address acoustic, fire proofing, fabrication, transport and lifting challenges. It was fabricated as cassettes made out of Tecbeam floor joists that had been constructed into panels with engineered Promat floor sheeting, assembled off-site. These were shop drawn for required accuracy and lifted in by cranes, creating a layered construction.
Each floor level (averaging 850m2) of The Green, was completed in around 11 days.
“The prefabricated floor system was a product of collaboration between Irwinconsult and Australand to address acoustic, fire proofing, fabrication, transport and lifting challenges. The resulting floor system was fabricated as cassettes made out of Tecbeam floor joists that had been constructed into panels with engineered Promat floor sheeting, assembled off-site.” Mark Paterson, Associate Director and Phil Gardiner, Managing Director – Irwinconsult.
With timber buildings exceeding two levels not deemed to comply with AS1684, all load bearing walls were fully engineered for both the vertical and wind design loads. Special consideration was given to the detailing of interstorey wall connections for walls for transfer of design loads. All the walls were prefabricated using typical timber frame construction methods off site then installed onsite as fabricated wall panels.
Major program advantages over conventional construction became evident during the construction of the first level. Each floor level (averaging 850m2) was completed in about 11 days. This included all the internal walls being installed as part of each level’s construction cycle and no back propping was required as the floors could span from load-bearing wall to load-bearing wall.
The actual timber construction time (including roof trusses and floor cassettes) was only 12 weeks out of the 12 month build program. As such, this new construction methodology reduced the build time for each floor by a week, allowing the building to be completed one month earlier than originally programmed. ■
Karlie Collis – College of Structural Engineers (Chair), Engineers Australia.
