It was New Zealand’s biggest, most complex seismic strengthening project, costing $83.5 million and taking 4½ years, but now Wellington’s tallest skyscraper stands firm once more. Reporter Matt Stewart looks behind the logistics.
When it was completed in 1991 The Majestic Centre’s 28 floors redefined the skyline but after the Canterbury earthquakes in 2011 fears abounded that Wellington’s tallest building could cause deadly chaos if it buckled in a quake.
So owners Kiwi Property assessed its portfolio and found the building was a low-to-moderate earthquake risk, sitting between 34 and 66 per cent of the new building code.
That put it above the 33 per cent danger zone, but the risk was still deemed too high so in 2012, work began on the $35 million project to bring it up to 70 per cent of code. A year later the decision was made to strengthen it to 100 per cent, and by 2014 the budget had rocketed to $83.5m.
Costs blew out because of the complexity of the structural engineering involved and the logistical challenges of working in a fully operational building.
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“This has been one of the most complex seismic strengthening programmes ever undertaken in New Zealand with our programme of works undertaken in stages over four-and-a-half years to keep the building operational throughout,” Kiwi Property chief executive Chris Gudgeon said.
Now a low seismic risk after practical completion on January 31, the tower has a performance-rating equivalent to 100 per cent of New Building Standards.
“The strengthening of The Majestic Centre is a world-class example of what can be done to improve the seismic performance of buildings while keeping them operational,” Kiwi Property commercial general manager Michael Holloway said.
Highly technical, the operation required diggers being deconstructed and rebuilt inside the basement.
New foundations, including 38 new 14-metre-deep piles, required one of the largest concrete pours in Wellington – 83 concrete trucks snaked out of the building and up Boulcott St.
The core of the building was wrapped in a full metal jacket and secured with 20,000 bolts. The holes for each bolt took eight minutes to drill.
The external panels of the tower weigh as much as an elephant and had to be re-secured to the building by hand.
As well as the foundations, a load-bearing circular beam at the base of the tower, the lift shaft walls and all 28 floors were strengthened.
The Earthquake Commission, Summerset Group Holdings and GM Commercial all renewed their leases with Kiwi Property during construction.
Construction began in the late 1980s and had to mould around the historic house of Dr Henry Pollen, which was moved further down Boulcott St and is now the General Practitioner pub.
The building stands at 116 metres eclipsing Wellington’s only other skyscraper – the State Insurance building – by 13m.
The site of was also home to the Majestic Cabaret, the legendary ballroom dance hall.
In the early 1990s soon after The Majestic Centre was completed that dance tradition continued – the building’s panoramic top floor became part of Wellington’s burgeoning underground dance music scene when it hosted an all night rave.
BY THE NUMBERS * 1300 cubic metres of concrete was poured * 1325 tonnes of structural steel was installed * 53.2km of post-tensioning strand was laid using 53,500 bolts and anchors * During peak construction, crews worked in two shifts covering 21 hours a day, seven days a week.