Design standards and building laws will be reviewed in response to an investigation into structural damage to Wellington’s Statistics House in the Kaikōura earthquake, Building and Construction Minister Dr Nick Smith says.
Dr Smith today released an independent panel’s findings into the performance of the building during the 14 November 2016 quake, focussing on its design and construction, and the land influences on it.
“The performance of Statistics House in the Kaikōura earthquake was unacceptable and could have caused fatalities. This quake was large and unusually long but a modern building like Statistics House should not have had life-threatening structural damage. The building was designed to the industry practice of the time but this did not fully account for the effects of beam elongation during an earthquake, an issue that was deficient in the Concrete Structures Standard at the time of the design.
“The design flaw is quite specific to highly ductile framed concrete buildings with pre-cast floor slabs and particularly those with multi bay frames. We need to follow up on similarly designed buildings through councils and engineering companies so that where it is a problem, it can be rectified. This has already been done in respect of Wellington as a consequence of the preliminary findings in Statistics House but now needs to be followed up elsewhere. We also need to amend the Concrete Structures Standard to ensure newly designed buildings are adequately designed to cope with beam elongation during long duration earthquakes. This will be done this year.
“A compounding factor was geological basin effects that are not well understood but which have also been observed in other earthquakes internationally. This is not to do with reclaimed land but the amplification of ground shaking in a basin. This phenomena is similar to the way sea waves respond to a wall in an enclosed bay. This is an area of seismic science that needs further research, particularly in respect of Wellington, and to be considered as part of a review of the Earthquake Actions Standard.
“There is a building law issue that arises from this report on which I have asked officials to report. The Ministry of Business, Innovation and Employment (MBIE) has limited powers to follow up on design deficiencies like those identified in this report beyond those specifically provided for following civil emergencies. This means MBIE cannot require building owners to follow up on these sorts of potentially serious technical problems. I have asked MBIE to report on whether additional powers are needed in the Building Act.
“New Zealand is at the cutting edge of international seismic design standards but we have not yet solved all of the potential ways a building can fail. Most buildings in Wellington performed well despite the ferocity of the Kaikōura earthquake. We need to take the opportunity following such earthquakes to learn as much as we can and to further strengthen our standards and systems to improve building safety for the future.
“These detailed issues over the performance of modern buildings are important for improving design standards but they should not divert attention away from the far more significant risk to life of older buildings. The Kaikōura earthquake was sufficiently distant from Wellington that the city did not get the dangerous high-frequency shaking that poses the greatest risk to life.
“The largest safety gains for Wellington are to be made in the initiatives requiring unreinforced masonry facades and parapets to be tied back over the next year and all earthquake-prone buildings under 34 per cent of Building Code to be upgraded under the new law coming into effect on 1 July.”
The Statistics House investigation report is available at http://www.mbie.govt.nz/info-services/building-construction/safety-quality/statistics-house-investigation