Some checks on CTV building left out - expert
More could have been done during an inspection of the Canterbury Television building after the September 2010 earthquake, a United States expert said yesterday.
Californian structural engineer Brian Kehoe had earlier backed a Christchurch engineer's report that stated no serious structural damage was evident after the September quake.
Kehoe gave evidence yesterday at a royal commission hearing into the CTV building's collapse in the February 2011 quake.
Kehoe said he endorsed findings by engineer David Coatsworth, who spent four hours doing a visual assessment of the building on September 29, 2010.
Coatsworth found cracking and damage in the building, but concluded the structural damage was minor and did not require a more detailed structural analysis.
He did not have structural drawings of the building, although he had tried to get them, and he recommended repairing the cracks he saw.
He did not consider how the building would fare in another major quake and did not recommend a seismic analysis be done.
Kehoe said that, on the basis of Coatsworth's field notes and photographs taken on the day, he agreed with the conclusion that damage to the structure of the building was "minor ... at worst" and "for the most part" it did not warrant structural repairs.
Questioned by counsel assisting the commission, Marcus Elliott, Kehoe conceded Coatsworth could have looked at some areas more closely, which would still be "relatively non-invasive".
Coatsworth could have lifted floor or ceiling tiles in more locations than he did, and looked at different parts of the building, Kehoe said.
Coatsworth could also have reviewed the design drawings when they became available from the council on October 6, looked at the connection of floor slabs and the north core, and "maybe" looked at more interior beam column joints.
Even if Coatsworth had done these things, he may not have reached a different conclusion.
"I can't think of anything I would have done differently," Kehoe said.
But "given the limited damage he [Coatsworth] saw", there was not enough visible damage to warrant doing a seismic analysis or pursuing the structural drawings.
Fellow assisting counsel Mark Zarifeh said a lack of training for inspectors and engineers conducting post-quake rapid assessments, perhaps through lack of opportunity, had "come through very clearly" in the inquiry.
Kehoe agreed, saying written guidelines and training on what engineers and building inspectors should look for in different types of quake-damaged buildings to uncover structural damage would be beneficial in New Zealand.
In the US extensive training was available.
"Other than the guidelines for territorial authorities, I don't believe there is anything else [in New Zealand]," he said.
UP TO 200 HOLES DRILLED, SAYS CONTRACTOR
Claims that up to 200 holes were drilled in the Canterbury Television building may be true, but that did not mean they affected the strength of the building, an engineer says.
Daniel Morris, former owner of Knock Out Concrete, yesterday outlined his "hazy" memories of work his company did on the CTV building to a royal commission of inquiry into the building's collapse in the February 2011 quake.
Morris said his staff drilled up to 200 holes into the building, including about 50 into structural concrete beams, some time between 1995 and 2000.
He had no records to verify the work and could not remember why they were drilling or who contracted his company to do it.
Fletcher Construction chief engineer Graham Frost, who worked with Urban Search and Rescue on the CTV site in the days after the quake, said it was common for buildings to be drilled to run cabling through.
He did not see evidence of any drilling that had affected the structural integrity of the CTV building, but if this had occurred on the lower levels, the concrete was so badly damaged by the time it was lifted off the site it would have been impossible to see.
It would be unusual for drilling to take place in structural beams. It was more common to drill into slabs, he said.
Morris had told the commission that his crew were "all care, no responsibility".
"We cut where the main contractor marked," he said.
"We were told to just cut through reinforcement if we needed to."
It was the responsibility of the contractor to obtain permits to drill the holes. Morris said that when he heard the CTV building had collapsed he "immediately thought about all the holes that had been cut in the beams".
He contacted the Department of Building and Housing and told it about the hole-drilling work.
Morris said during questioning that this kind of drilling concerned him.
"I used to say, 'This isn't right ... to the odd foreman'," he said.
Frost, who gave evidence last week, was surprised Morris could not remember where in the CTV building the drilling was done.
He assumed the collapse had played heavily on Morris' mind.
"He'd be thinking, 'I turned it into honeycomb'," Frost said.
"It all depends where the holes were drilled. It doesn't necessarily cause a problem."
- The Press