Premier global construction company, Multiplex, has completed the new tower and retail precinct at 80 Collins Street, effectively delivering one of the largest brand new commercial office precincts in Melbourne's CBD.

The 80 Collins Street precinct is owned by Dexus and Dexus Wholesale Property Fund following QIC's divestment of the asset in May last year. It was delivered to completion by QIC GRE.

Located at the "Paris end" of Collins Street, the precinct comprises a new 38-level office tower providing circa 43,000 square metres of premium office space and a 255-room boutique hotel as well as major refurbishments to the existing 47 level A-grade office building.

Base building design was undertaken by high-profile architects Woods Bagot in collaboration with Dutch firm UN Studio on the facades of both the new office tower and hotel.

The extensive retail precinct spans the ground and podium levels, while the three surrounding streets (Collins, Exhibition and Little Collins Streets) are connected through a series of laneways, linking the new hotel to both office towers.

The new office tower features a stunning faceted glass exterior cantilevering towards Collins Street. The interior features flexible floor plates with the ability to create inter-floor links.

At 216 metres tall, 80 Collins Street boasts panoramic views across Melbourne.

"We are proud to deliver this new landmark development to Collins Street, it is an exciting new addition to Melbourne's premium retail and office precinct and breathes fresh life into the rich history of the area," said Graham Cottam, Regional Managing Director at Multiplex.

"80 Collins Street was an extremely complex build with the new office tower constructed to cantilever 12 metres over existing buildings on Collins Street, the first time this engineering feat has been achieved on such a scale. It is built to withstand 30,000kN tensile force through the concrete core, which is three times that of what has been previously built in Australia."

According to Cottam, Multiplex developed an innovative construction method using steel ducts to facilitate the feeding of steel bars and reinforcements to form a new tension bar system. The system effectively withstands and transfers the tensile loads of the cantilevered structure to the building core, without the requirement for additional structural support columns.

Other innovations in the construction of 80 Collins Street include the first use of a double-decker lift system in Australia. Two lift cars stacked on top of each other allow the lift to double its capacity without requiring extra space within the lift core. This allowed 18 lift cars to be operational within nine lift shafts, minimising the size of the lift shaft and maximising NLA for the tower.

Construction commenced in April, 2017 with some 800 workers on-site every day in peak periods and approximately 7,000 tonnes of structural steel and 30,000 cubic metres of concrete used throughout construction.

80 Collins Street includes a number of ESD innovations to achieve WELL readiness and a 6-Star Green Star rating for the base build including a chilled beam mechanical system to allow for passive temperature control. The tower also features intuitive lighting control, with thousands of individually controlled Tridonic sensor lights responding to the movement of inhabitants throughout the building.