50 La Trobe Street, Melbourne: Hickory worked with client Blue Sky Funds, architect Hayball and Structural Engineers Rincovitch to deliver a design that preserved the building’s original facade; an effort welcomed by Melbourne City Council and heritage groups.
Hickory Building System (HBS) has been a pioneer in modular construction through its Unitised Building (UB) modular system. However, the application of the UB system in a high rise building was limited due to inadequate structural integrity and strength. Hickory Group invented the next generation of modular system called the Hickory Building System (HBS) or HBS1 to overcome these issues.
Now, another refinement on the HBS1 system, HBS2, has been applied successfully to a 43-storey student accommodation building at 50 La Trobe Street, Melbourne. HBS2 enables high-rise buildings to be made offsite in a series of manageable sections that can be assembled on site. The majority of the work is performed in a controlled factory environment, resulting in 30 per cent reduction of wasted material.
Construction entails prefabricating floor slabs, facades and Sync bathroom pods in Hickory’s factory and transporting these to site for fast and efficient installation. A transfer structure at level 2 has been designed to receive the HBS modules from level 3. Matching loose props were installed to receive the HBS modular system.
The method of lifting 285 HBS modules with an appropriate lifting frame for 43 levels was designed and certified by a third party engineer. HBS engineers carried out a full scale test to lift the biggest modules. In addition, the use of a pre-assembled facade has the added safety benefit of forming a protective barrier for workers on each floor. Further, the modules’ factory fabrication at ground floor level is another safety bonus for workers in high risk, high level areas.
Most of the shear, core and load bearing walls have been constructed using precast walls with wet joints. Some major structural walls and off form finish architectural requirements were completed with in-situ concrete. This eliminated the traditional jump-form construction completely.
HBS2 prefabricated modules consist of a concrete light weight floor with recyclable temporary props attached to the floor. The tops of the props are tied together using steel perimeter. These temporary props can then be removed and recycled. The facade is attached to the perimeter steel beam and is held laterally via a top angle. As the modules come with the facade attached, the critical path of onsite installation has been made a non-critical activity, which greatly reduces project duration.
All module slabs have been stitched in-situ using innovative HBS tongue joints.
HBS modules were developed to have the curtain wall and facades attached at the offsite prefabrication stage; and experts were engaged to come up with innovative fixing systems with adequate tolerance. A precision manufacturing procedure was developed to achieve this.
The projected outcome for this scheme will mark a new modular milestone. At nearly 150 metres high, 50 La Trobe Street will be one of the world’s tallest student accommodation projects to use prefabricated construction methods. ■
Karlie Collis – College of Structural Engineers (Chair), Engineers Australia.
Dr Shan Kumar Chief Engineer – Innovations / R & D / Design & Development, Hickory Building Systems.