The Canterbury earthquakes royal commission has slammed the design of the ill-fated CTV building, saying a building permit should never have been issued.
The commission’s final report calls on changes to be made to the Resource Management Act to ensure local authorities better acknowledge the effects of earthquakes and liquefaction.
Prime minister John Key has welcomed today’s release of the final 83 recommendations but has stopped short of supporting them, saying the government will release a “full and comprehensive response” by mid next year.
Volumes 5-7 of the report looked at a number of issues, including:
- The investigation into the collapse of the CTV building.
- The roles and responsibilities in the building sector, including the assessment of buildings after earthquakes.
- The training of civil engineers, and the organisation and regulation of the engineering profession.
- The building consent process.
- Local government management of earthquake risk.
The collapse of the CTV building during the February 22 quake killed 115 people.
The royal commission said its failure was severe, even though it was designed under relatively recent building standards.
“The engineering design of the building was deficient in a number respects. While there were elements of the applicable code that were confusing, a building permit should not have been issued for the building as designed.”
It said there were a number of inadequacies in the construction of the building.
The report listed a number of reasons, in the authors’ opinions, for the collapse, including:
- The designer failed to consider properly or adequately the seismic behaviour of the gravity load system. In particular, no consideration appears to have been given to load tracking through the beam-column joint zones which were easy to construct but lacked ductility and were brittle in character.
- The columns were inadequately confined and could not sustain the deformation they were required to undergo without failure.
- The correct tie forces between the floors and the north wall complex were not determined and the load path was not tracked between the wall and the floors.
As a result, the report recommends the Ministry of Business, Innovation and Employment should consider developing guidelines for structural failure investigations, including circumstances in which sites should be preserved for formal forensic examination.
Other buildings nationwide, which may have the characteristics which lead to their collapse in a major earthquake, should also be identified.
The report has recommended buildings are assessed for their potential seismic performance.
In doing so, the individual structural elements should be examined to see if they have capacity to resist seismic and gravity load actions in an acceptably ductile manner.
The report also wants relatively simple methods of analysis such as the equivalent static method and/or pushover analyses to be used to identify load paths through the structure and the individual structural elements for first mode type actions.
The significance of local load paths associated with higher mode actions should also be considered.
The RMA has also come under the spotlight in the report, with the royal commission recommending changes to sections 6 and 7 to ensure regional and district plans (including the zoning of new areas) are prepared on a basis which acknowledges the potential effects of quakes and liquefaction, and to ensure those risks are considered in the processing of resource and subdivision consents.
It wants consent applicants to be required to undertake geotechnical investigations to identify the potential for liquefaction risk, lateral spreading or other soil conditions which may contribute to building failure in a quake.
“Where appropriate, resource and subdivision consents should be subject to conditions requiring land improvement to mitigate these risks.”
The report has also called for better information to keep regional councils and territorial authorities informed about the seismicity of their regions and districts.
It wants regional councils to take a lead role and provide policy guidance, since seismicity should be considered and understood at a regional level.
Mr Key says the government owed it to the 185 people who were killed in the February 22 quake, along with their families, to find answers as to why some buildings “failed so severely”.
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