Statistics House quake performance unacceptable, inquiry finds
Wellington's Statistics House performed unacceptably in the November Kaikōura earthquake and could have caused fatalities, an independent investigation has found.
Two floors of the building partially collapsed in the Nov. 14 earthquake, and the building was declared a no-go zone the next morning, with entry prohibited since. The investigation, commissioned by the Ministry of Business, Employment and Innovation, didn't consider the future use or reparability of the Statistics House building.
The independent panel's investigation found that four factors contributed to the partial failure of lower floor segments: the high level of flexibility in the building's design, the precast style of floor construction, the magnitude and duration of the 120-second earthquake, and the amplification of ground shaking by the geological basin beneath Wellington.
"This quake was large and unusually long but a modern building like Statistics House should not have had life-threatening structural damage," Building and Construction Minister Nick Smith said. "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 building's fourth floor had had remedial work done after the Canterbury earthquakes after a seismic review identified potential performance issues, and that part of the building performed well in the Kāikoura earthquake.
The panel made four recommendations. It said existing buildings in the Wellington region with a similar design that may have been damaged by the Kaikōura earthquake should be investigated for problems, and the industry should be notified about issues with precast floor systems. MBIE should also access technical expertise to consider the implications for this type of design for new buildings, and should review and undertake research into the provisions in the Earthquake Actions standard to ensure they reflect current knowledge, it said.
Smith said the government will amend the Concrete Structures Standard this year to ensure new buildings can cope with beam elongation during earthquakes, and he has asked MBIE to report whether it needs additional powers under the Building Act to require building owners to follow up on problems.
"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 July 1," Smith said.