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The Canterbury Television building's flawed design and construction went unnoticed by Christchurch City Council officials who issued its consents.
And a known weakness in its structure was not rechecked after the September 2010 earthquake, a specialist earthquake engineer and government adviser says.
The Department of Building and Housing yesterday released a technical report on the collapse of the central Christchurch CTV building in last February's quake.
The quake, close to the city centre, killed 185 people, 115 of whom died in the CTV building when it collapsed and caught fire.
Witnesses said the building collapsed in "seconds".
Building and Construction Minister Maurice Williamson told Radio New Zealand today that councils were supposed to check plans met the building code of the day before giving building consent.
They were then supposed to conduct inspections as the build went along before a final compliance check.
"I assume that in the vast bulk of cases that always occurs properly, but in the end it certainly didn't happen in this case," he said.
Christchurch City Council chief executive Tony Marryatt last night confirmed the council issued a building permit for the building in 1986.
Records showed the permit was issued "following the receipt of designs, specifications and construction documents provided by independent engineers and architects employed by the owner".
He said the council's building file had been provided to the Canterbury earthquakes royal commission and the council would co-operate with the commission's further investigations into the collapse of the building.
"The technical report will be considered as part of the royal commission's public hearings later this year, and the council will be a party to those hearings," Marryatt said.
Williamson said there was a need to look at buildings built similarly to the CTV building.
The Department of Building and Housing had identified 352 buildings and had inspected half of them, which were found to be "reasonably OK".
The report released yesterday looked only for the cause of the collapse, not who was to blame for it, he said.
The department's long-awaited report, a key piece of evidence for the commission, found the building did not meet the standards of the day.
The report, produced by an expert panel, identified three "critical" factors in the collapse:
- The intense horizontal ground shaking.
- Brittle columns.
- The asymmetrical layout of structural walls, causing the building to twist in the quake and place extra strain on the columns.
Also, concrete in the columns was significantly weaker than expected.
While the department found no fault, it referred the report to police and the Institution of Professional Engineers. Both bodies are considering further action.
Police Assistant Commissioner Malcolm Burgess said police would seek legal advice and assessment of the department's evidence, which would determine the next step.
He said it would be wrong to suggest the assessment would naturally lead to criminal charges.
Construction of the CTV building started in 1986 and the department's report stated "drag bars" were installed to the three upper floors in 1991 to improve the connection between the floor slabs and the main structural wall on the north side.
David Hopkins, a specialist consultant in structural and earthquake engineering, who managed the expert panel for the department, yesterday said the drag bars were added because of a perceived weakness in the building's design.
The report found the building's collapse was "almost certainly" initiated by the failure of one or more columns on the east wall, facing Madras St.
Hopkins said he could not rule out that the floor slabs had disconnected before the columns failed.
Asked whether the floor connections were specifically inspected after the September 2010 quake, he said: "No, I don't believe it was."
The department investigation - which included site inspections, materials testing, a review of existing reports and photographs, and witness accounts – concluded the September and December 26 quakes in 2010 did not significantly weaken the structure.
"We assumed that there was no separation [first]," Hopkins said.
"There was no evidence that was discovered that that was the case."
He said if the building had met the 1986 code, it would have had a greater chance of staying standing last February.
Building department chief executive Katrina Bach said yesterday the investigation called into question the design, construction and consenting of the building.
However, she said the earthquake was an exceptional event and the CTV building had unique circumstances.
She said the department was reviewing plans of 350 high-rise buildings, including 23 in Christchurch, that were built in the same period and could have "non-ductile" columns and asymmetrical design.
The review would be completed by May.
The department accepted the report's five recommendations.
Council inspectors gave the building a green placard after a rapid assessment on September 5 2010 and another green placard on September 7 "after the building was assessed by three senior council building officials".
An October 6, 2010, damage report, undertaken by a consulting engineer for the building owner, identified minor structural damage and non-structural damage, including cracks in columns.
Repair work was being done when last February's quake struck.
The department report said an independent consulting engineer's review of the building in 1990, for a potential buyer, raised concerns about how the floor slabs were attached to the northern structural wall.
"These concerns were conveyed to and acknowledged by the design engineer," the report said.
The city council told the department that the building owner made no application for the 1991 work.
The department report said of the drag bars: "These connections were vital to the integrity of the building since the walls provided lateral stability and strength to the building."
The owner's engineer may not have been aware the drag bars had been installed, the report said.
NO BLAME GAME FOR CTV FAMILIES
A Christchurch woman whose husband was killed in the CTV building says she is "not interested in blame".
Relatives of the 115 killed, and the building's tenants, were briefed yesterday on the contents of the Department of Building and Housing technical report, which found the building failed to meet standards when it was constructed in 1986.
Prue Taylor, principal of Christchurch Girls' High School, lost husband Brian last February 22. He was the director at King's Education.
"I think all of us would like some explanation and they are doing the best they can," she said.
Mike Didham, whose wife, Joanna, worked for CTV, said it was good to hear why the building collapsed.
"I always wanted to know why that one. It's just unlucky that our people were in it."
Didham was concerned there were other buildings in Christchurch that did not meet the building standards.
"If there is potential for any other building to come down, they need to close it off or do whatever they need to do to make it safe," she said.
Alison Bennie, whose partner, Dr Dominic Bell, was working at The Clinic in the building, was surprised by the presentation because she believed the department was going to tell them "s... happens''.
''They had done a fantastic job and genuinely tried to find out what was going on," she said.
Knowing how and why the building collapsed gave her a sense of closure as Bell worked on the eastern side of the fourth floor where the building apparently initially caved in, meaning he may not have suffered for long, she said.
Bennie said holding someone accountable may not achieve anything.
Brian Walker, whose daughter, Amanda Uriao, was a CTV saleswoman, did not go to the briefing because he was out of town.
The findings did not surprise him. "I know she has died and I don't want to know much more than that."
Walker said allocating blame was not going to bring his daughter back.
"You can't change a hell of a lot. I mean, we are angry and everything else but you can't rectify it."
A police probe would only make the victims' families be reminded of it all the time and make it "go on and on", he said.
- © Fairfax NZ News
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