Implosion 'test case' for Christchurch

Posted 17 Jul 2012 by MediaStuff Popular
Posted in Media , Demolition
This item was posted on the Stuff.co.nz website - click here to view the original

The media is given details about the implosion of the Radio Network Building today.

 
 

The implosion is expected to see the 14-storey Worcester St building come down in about 7.7 seconds.The demolition of Radio Network House could be a "test case" for further implosions in Christchurch's central city.

The demolition, which will take place on August 5, will be New Zealand's first ever building implosion.

Work is underway to strip  the interior of the building so it will be empty when it implodes.

Naylor Love is the prime contractor and Ceres New Zealand is the subcontractor responsible for the demolition.

Ceres is partnering with United-States based company Controlled Demolition Inc, which has carried out 9000 implosions worldwide.

Canterbury Earthquake Recovery Authority (Cera) general manager of operations Warwick Isaacs said as the implosion was the first in New Zealand the methodology had been acutely scrutinised by Cera engineers.

"We are satisfied that the contractors have covered all the key risks in great detail and that the demolition will be safe and successful."

Isaacs said the implosion could act as a "test case" for other suitable buildings in the city.

He was not aware of any other buildings earmarked for implosion.

"We're very excited that it allows the demolition of this building to come down in a much quicker fashion than what it would've come down.

"So from our point of view what that does is expedite the recovery of the central city and helps us move on with the rebuild more quickly," Warwick said.

Building owner Greg Hedges said it was "ridiculous" that implosions had not been used to assist in the rebuild effort.

"We're using out-dated technology when this is available to use ... We see the big issue as trying to speed up the demolition of buildings that will in-turn speed-up the building and recovery of Christchurch."

Ceres long term recovery manager Bill Johnson said imploding the building would not only shorten the demolition process by about six weeks but also save money.

The cost of the implosion is close to $1 million and is covered by the owner's insurance.

In comparison, alternative methods of demolition were quoted at about $1.2 million.

Johnson said the implosion would be achieved by strategically placing small explosives charges in holes drilled in the support columns of the building.

A total of 60kg of explosives would be used to bring down the 6,100 metric tonne building.

"By carefully controlling the sequence of the firing of the charges, the demolition of the building will occur by utilising gravity. The weight of the upper part of the building will destroy the lower portion."

But it is not yet known who will push the demolition button and the role could be auctioned to raise funds for charity.

"We're trying to sort out the liability of that," Johnson said.

"I've seen them go for $6000 ... considering this is the first in New Zealand I'm going to have high hopes," Johnson said.

He reassured that the implosion would result in "minimal" shaking as the lower levels of the building would absorb the "energy" of the impact.

An exclusion zone fence will be installed, about a block in either direction of the Worcester St building, to ensure the safety of the public.He said the shaking could not be compared to a quake as the "vibrations were different".

Given the lack of activity in the area, the recommended zone was extended as a precaution, Johnson said.

Implosions have gone wrong in the past.

The Royal Canberra Hospital implosion resulted in the death of 12-year-old Katie Bender.

Nine other people were also injured, as large fragments of masonry and metal were flung up to 650 metres from the demolition site.

After the Radio Network House implosion, all public roads will be cleared before being reopened to traffic.

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