The engineer whose company designed the Canterbury Television (CTV) building has described the "shattered feeling" on learning it had collapsed in the February 2011 earthquake.

Alan Reay, director of Alan Reay Consultants Ltd (ARCL), told the Canterbury earthquakes royal commission today that he did not know the building's fate straight away.

"I learnt it later that day," he said.

"I was already fairly shocked having been in the city. I guess it just added to the shattered feeling that I had."

Earlier, Reay said he was still "dissatisfied" with a report on why the building collapsed in the quake.

He told the commission that people "deserve to know all the aspects of why the building failed".

A Department of Building and Housing (DBH) report identified serious design and construction flaws in the building and found it did not meet building standards.

Reay said the cumulative effects of quakes before the February 2011 shake should have been taken into account.

"The cumulative damage and fatigue effects on the structural elements should be included in the modelling and have been insufficiently accounted for in the analyses run as part of the DBH report."

More experiments, such a reduced-scale model of the CTV building being tested on a shake table, should have been done, he said.

"Completing these analyses will take considerably longer than the time that was available to the authors of the DBH report, but in my view ... the modelling to date is inadequate,'' he said.

"The royal commission ... does not have access to the best available information to assist with understanding the causes of the collapse."

The strength of concrete used in the building also needed further attention, Reay said, as DBH investigators assumed much lower strengths than those specified in design documents when they did tests.

"The probability of concrete strengths as low as this was negligible unless the contractor deliberately set out to order substantially under-strength concrete and mishandled the concrete workmanship on-site."

The department may have collected artificially low data if they did strength tests on concrete damaged by the fire that broke out in the rubble after the collapse, he said.

Reay is being cross-examined by counsel assisting the commission Stephen Mills, QC.

Lawyer slams CTV investigation

Hugh Rennie, QC, acting for ARCL, earlier told the commission the DBH report overstepped its mandate.

"These conclusions made by the report writers were not part of their terms of reference," he said.

"It was inappropriate for the DBH to claim certainty before this royal commission considered the CTV building under terms of reference which are more extensive and with a much greater range of information."

The DBH report, released publicly in February, found that the building failed to bend sufficiently during the quake and pointed to poor strength and layout of its key shear walls.

It did not meet the building or design codes for when it was built, the report concluded.

Rennie said ARCL's intention since the CTV tragedy was to "investigate and so understand what happened", but attempts to co-operate with investigators, including DBH, had been "rebuffed".

"This rebuff is contrary to the long-established professional principles and rightly or wrongly was seen as an implied accusation and with degrees of pre-judgment,'' he said.

"The consequence has been that ... ARCL were left to conduct their own parallel investigation with such information as they could obtain."

Reay would testify that multiple elements of the DBH investigation were deficient, Rennie said.

This included concrete strength calculations, retention of building material as evidence and inadequate computer modelling of the collapse.

Reay had little direct involvement in the CTV design, Rennie said.

Most of the work was done by engineer David Harding, who logged more than 300 hours on the job, while Reay did just 3.5.

Reay and engineer John Mander would give evidence they believed the CTV building complied with 1980s building standards.

However, structural engineering professor Nigel Priestley today voiced concerns about Mander's report on the building to the commission.

Mander's conclusion that it was "inevitable that maximum vertical load and maximum drift would occur simultaneously" in the CTV collapse was contradicted by analytical evidence, Priestley said.

"This use of definitive statements is something that I regret to say that I find not infrequently in Dr Mander's report."

Mander's interpretation of concrete testing - the strength of concrete used in CTV is a focus of the inquiry - was "doubtful", he said.

"The subdivision of ... test results between the storeys is entirely arbitrary, I believe, and conjectural and rather dangerous with such a small sample."

Reay and Mander are scheduled to give evidence this afternoon.

CTV building had 'undesirable' design - engineer

Priestley earlier told the commission the CTV building's design was "undesirable" for resisting earthquake shaking.

The building's key support wall, or shear wall, would ideally not be on the exterior, he said.

"There certainly have been other buildings designed in such a fashion with an external shear wall, but primarily in non-seismic regions,'' he said.

"It's quite clear that from a seismic point of view that this is an undesirable building configuration and [that makes it] very difficult to make it perform well [in quakes]."

Priestley said extra care was needed to design a building like CTV.

"The building would need to be designed to best practice and with considerable additional care in the design. In my view there is not evidence that that was done."

Rennie suggested to Priestley the codes of the day "did not contemplate a building of this architectural concept", but the engineer rejected this.

"I don't believe you can draw that conclusion. The building codes in general are not built around the concepts of different structural forms."

Spiral steel reinforcement within the concrete columns in building may have been too widely pitched to cope with the force of the February 22, 2011 earthquake, which triggered its collapse, Priestley said.

"I don't believe that the code would have permitted for an element which is subjected to shear, which these columns certainly were, and quite high shear ... that a spacing of greater than half of the diameter of the column would be acceptable."

Reay has dismissed the  DBH report that found construction and design flaws in CTV were "technically inadequate".

The report also concluded the building did not meet building standards applicable in 1986.

''ARCL is extremely disappointed with the process the DBH has followed and the subsequent conclusions in the reports. It has not carried out the investigations it should have," Reay said after the report's release in January.

''Some of the assumptions made in the reports are highly questionable. As a consequence, the report's findings are not conclusive. In fact, in many areas they may be flawed.''

''I have huge empathy for the families waiting for answers, but these reports are technically inadequate. We owe it to the families of those who died in the CTV building to conduct a robust and thorough investigation using the best technologies and methodologies available. This has not occurred."

 

Priestley also dismissed a conclusion from Mander that the building was "innovative" today.

"It might be innovative but in a very undesirable sort of fashion. I cannot accept that this is an innovative structure in a desirable form for seismic resistance," he said.

Priestley also gave evidence on the joints that connected the CTV building's concrete columns with horizontal beams.

The strength of the joints has come under scrutiny at the commission.

It could not be known whether better steel reinforcement in the joints would have kept the building standing, Priestley said, but theoretical tests suggested it could have.

"I can't say that the structure would have survived but I can say the ... time-history analysis would not have predicted failure," he said.

- © Fairfax NZ News

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