Engineer would not have approved remedial work
Christchurch Earthquake 2011
The engineer who first identified that the Canterbury Television building did not meet building standards says he would never have approved the strengthening work eventually done to try to fix it.
Holmes Consulting Group (HCG) engineer John Hare was asked to examine the CTV building for a potential buyer in 1990.
He told the Canterbury earthquakes royal commission today that he found the connections between the building's floors and key support wall were not strong enough.
"I picked this up fairly quickly as there appeared to be no connection detail for the walls on either side of the lift shaft."
Quoting from his 1990 report, Hare said that in the event of an earthquake "the building would effectively separate from the shear walls well before the shear walls themselves reached their full design strength".
He advised the company that designed the building, Alan Reay Consultants (ARCL), of his concerns and drew up draft strengthening plans that costed the "potentially expensive remedial work" at $14,000.
Soon after, the potential buyer, the Canterbury Regional Council, pulled out and HCG was ordered to stop work.
ARCL continued with the remedial work itself but installed ties only on the top three levels. Hare's draft recommended ties on all five levels above the ground floor.
"The [ARCL] remedial detail ... differed in several ways," he said.
"I would not have agreed to the ARCL remedial detail had I been consulted about it at the time."
Hare told the commission he had discussed the installation of ties between the floor and north shear wall with ARCL engineer Geoff Banks before his work on the building ended.
Banks raised the possibility of not needing ties on five levels, Hare said, but he would have been "reluctant to agree" to such a move.
"It isn't something I would think would be obviously what you would do. I would have said that the absence of a tie meant that a tie should have been put in there, so I would have been reluctant to agree to any transfer of load,'' he said.
"It would have been just as easy in my view to put a tie in."
Calculations done by ARCL in October 1991 when it did the remedial work appeared to have been for this purpose, Hare said.
"It [appears they] were carried out by [ARCL] to check whether loads ... can be transferred to [other walls]."
Hare agreed with Banks' counsel Helen Smith's contention that his views on ARCL's work was clouded by hindsight.
"It's difficult when giving your evidence to devoid yourself from the 22 years of knowledge and experience that we all now have in design, isn't it?" Smith asked.
"I agree with that," he replied.
It was hard to compare the two designs 22 years later, Hare said, as his own was just a draft and ARCL's was more detailed.
"I was asked to comment [on ARCL's remedial work] by the commission and have done so," he said.
Witness concerns not listened to
Witness reports that the CTV building was "livelier" after the Boxing Day 2010 earthquake "fell on deaf ears", an engineer says.
John Mander, a former University of Canterbury engineer now based in the United States, said earlier that concerns about movement voiced by CTV occupants before the disastrous collapse on February 22, 2011, should have been heeded.
"The human body is a wonderful motion sensor," he said.
"Although it may not be possible to accurately predict the magnitude ... it is very capable of understanding relative differences - this one is bigger than that one.''
Survivors of the collapse, which killed 115 people, reported extra "bounciness" in the building after the Boxing Day 2010 aftershock.
Mander acknowledged that nerves and heightened awareness after a major quake meant people were more sensitive to such movement, but their concerns were real.
"These [concerns] served to provide additional evidence and it should have rung alarm bells, but apparently these alarm bells that people were raising fell on deaf ears and nothing was done about it."
Earlier, Mander said cumulative damage from the September 4, 2010, quake onwards meant the building's seismic capacity on February 22, 2011, was lowered.
"What was happening was that the response was eating into these reserve capacities ... and that was the sign of these initial damages that were shown up."
Design faults over the building's eccentric layout may have exacerbated this, he said.
Commissioner Richard Fenwick said a CTV-type building would not meet today's building standards, but others like it did not collapse.
"That type of building is no longer permitted, and that's quite right too, but of course there are quite a few buildings in Christchurch of that type which survived and performed well," he said.
"Maybe that's the reason that they did," Mander replied, "because those other extraneous faults [were not there]."
A 1990 report by engineering firm Holmes Consulting Group found the building may not be code-compliant.
Drag bars were installed on the top three levels to strengthen connections between the floor slabs and the north shear wall, allowing for greater stability in an earthquake.
Evidence will conclude tomorrow.
- © Fairfax NZ News
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