Prior damage not bad, CTV inquiry told
The Canterbury Television building would have collapsed during the February 2011 earthquake even if it had not sustained previous quake damage, an inquiry has heard.
Structural engineers Clark Hyland and Ashley Smith, who co-authored a report on the collapse for the Building and Housing Department (DBH) this year, told the Canterbury earthquakes royal commission yesterday that damage from the 2010 quakes was minor.
"The results we got from the separate analysis for February, assuming an undamaged state at the start of that analysis, indicated failure, so regardless of whether we had some damage prior to that or not, we felt it would still indicate failure," Smith said.
Hyland said the "very little damage" sustained in previous quakes meant a sequence analysis – an investigation of the cumulative effects of all quakes up to February 22 – was not warranted.
"From an analysis point of view, that is not enough damage to even consider the sequence effects," he said.
The building collapsed in the February 22, 2011 quake, killing 115 people.
The DBH report, released in January, pointed to its failure to bend sufficiently during the quake and the poor strength and layout of key shear walls.
The building did not meet 1986 building standards, it concluded, but the findings were dismissed as "technically inadequate" by Alan Reay, director of Alan Reay Consultants Ltd (ARCL), which designed the building.
Counsel for ARCL, Hugh Rennie, QC, pressed Hyland on an October 2011 email exchange with fellow DBH investigation panel member Rob Jury.
Rennie said Hyland appeared to dismiss a possible cause of collapse cited by Jury after being put forward by the deputy chairman of the investigation panel, Nigel Priestley.
He quoted an email from Jury to Priestley and Hyland: "I also believe that it's likely as [Priestley has] suggested that the slab could have been cracked in the [September 4, 2010 quake] and possible that it had cracks adjacent to the wall prior to September."
Hyland said that scenario was analysed "quite vigorously", despite Rennie quoting an email response sent by the engineer less than 90 minutes later in which he was "stunned that [Jury] should rely on his instincts regardless of what the evidence showed".
"We treated that [scenario] with respect and we applied the analysis to it," Hyland told the commission.
"The evidence was that there wasn't any cracking in the slab adjacent to the north core. If you look at the evidence of the people who were in level 4, none of them mentioned cracking in the lift-lobby area, where you would expect this cracking to occur."
The DBH report found the collapse was due more to concrete column failure than damage to a concrete slab attached to the north shear core.
That core, a key support wall that included the elevator shaft, was the only part of the building to remain standing after the February 22 quake.
In a tense exchange, Rennie accused Hyland of being close-minded: "I think you had a settled view by October that [the cause of collapse] was a column failure and you weren't interested in any alternative proposition."
"I don't believe that's what's been shown, sir," Hyland said.
Reay is due to give evidence on Thursday.