Non-ductile columns and the asymmetrical layout of shear walls of the CTV building in Christchurch were unable to withstand the February 22, 2011 earthquake.
This was the main finding of a government-commissioned Department of Building and Housing technical investigation.
The government ordered the investigation, along with investigations into the failure of the Pyne Gould Corporation, Forsyth Barr and Hotel Grand Chancellor buildings, following the 6.3 magnitude earthquake, which claimed the lives of 184 people, including 115 in the CTV building.
The investigations included eye witness accounts, photographs, site examinations, sampling and testing of materials, structural analysis and testing of various hypotheses using established engineering models.
Three critical factors were found that contributed to the building’s collapse:
1. Intense horizontal ground shaking.
2. Lack of ductility in the columns, making them brittle.
3. Asymmetrical layout of the shear walls, making the building twist during the earthquake, placing extra strain on the columns.
The ductility of the columns (and strength) and the asymmetrical layout of the shear walls were found to have not met the building standards of the day.
The investigation into the 1986 CTV building was conducted by Hyland Consultants and StructureSmith.
The Department of Building and Housing established a group of engineering consultants to conduct the investigations, which were peer reviewed by an expert review panel, chaired by construction law expert Sherwyn Williams.
Other factors that may have contributed to the CTV collapse included low concrete strengths in some of the critical columns; exceptionally high vertical ground movement; possible interaction of columns and concrete spandrel panels (on the external face of the building), making the columns less flexible; separation of floor slabs from the north core of the building; structural influence of the concrete masonry walls, making lower floors more rigid than upper floors, which placed additional stress on the upper columns during the earthquake.
“Although it is not possible to be definitive on the sequence of the building’s collapse, the common denominator in all collapse scenarios identified by the expert panel was the failure of one or more columns on the east face of the building. This is consistent with eye-witness accounts of the building during the earthquake,” according to Department of Building and Housing CEO Katrina Bach.
Comments and questions
An anecdotal comment I heard was that some builders would put a hose into the mixer bowl but not limit the time water was poured into it.
The concrete strength would be as little as 8 to 10 MPa, compared with normally 30 to 40 MPa.
From memory, the CTV building was a stop - go construction when it was built. The first developer/builder went broke. Bit more done. Another stop. Then it was finished by some farmer investors. So no overall build or completion. Hodge podge. Then disaster.
In Auckland we should have grave fears for the construction safety of so-called "Chase" buildings, including that strange shaped creation omn Queen St behind The Civic Theatre. Whatever happened to those directors and CEO ? Did they move on to become serial offenders as did Rod Pratrecivic did after Euro National et al ?
In Auckland we should have grave fears for the construction safety of so-called "Chase" buildings, including that strange shaped creation omn Queen St behind The Civic Theatre. Whatever happened to those directors and CEO ? Did they move on to become serial offenders as did Rod Pratrecivic did after Euro National et al ?
My question is how many other buildings in the rest of NZ are in such a weak state? How do we find them and fix them? How can we prove that buildings are safe if someone wants to know?
My concern ranges from leaky buildings and Pike River to all the omissions that made the Chch earthquake such a disaster. Then there is the lack of financial regulation that has led to avoidable financial disaster. It seems we have too many shoddy practices in our country. I for one, want to change things for the better.
I think we need to rediscover the old values, morality and integrity that made our builders, bankers and people a proud nation.
Of course there are always the rotten apples that shirk their responsibilities. Accountability for failure helps, but is most effective if it leads to better processes that prevent failure.
We have the tools. These are good risk assessment and the statutory requirement to implement management plans involving audits, inspections and effective corrective action. A good example of this is the Building Warrant of Fitness programme or for that matter, a warrant for your car.
I am opposed to excessive red tape and compliance costs. Good risk management programmes should pay for themselves. After all, if your building or business is less likely to be destroyed in a disaster, your insurance premiums ought to be lower. Hopefully the savings will pay for much of the de-risking corrective action.
Remember that our disasters have been cripplingly expensive to individuals, taxpayers and our society as a whole and dwarf the cost of better practices. We owe it to those who have lost their lives, wealth and happiness to do a better job in future.
There was a TV3 program on this which showed that the council building inspector ( A Mr G Tapper) at the time refsed to sign off on this building and his superior (??) ended up signing the paperwork, probably after much pressure.
Perhaps this Council Building Inspector to Mr TAPPER, who approved the building should be answerable to this case before anymore lives are at risks....
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