Statistics House Investigation

The performance of Wellington’s Statistics House during the Kāikoura earthquake focused on the design, construction and land influences on the performance of the building.

Building and Construction Minister Nick Smith released the Independent Panel’s investigation into the performance of Statistics House on 31 March 2017. It found a combination of four factors contributed to the partial failure of lower floor segments.

Two of the factors – the flexible frames and style of floor construction – combined with significant shaking for up to 120 seconds, and localised amplification of the shaking, to compromise the support of the lower pre-cast concrete floor units on their framing.

The Kāikoura earthquake was a highly complex earthquake and is challenging existing seismic hazard models. More than twelve separate faults broke during the quake, including some that had not previously been mapped, and the frequency of shaking that arrived in Wellington 240km from the epicentre most affected mid-rise Wellington buildings.

The combination of factors that led to the partial collapse of floor units in Statistics House was not anticipated by the design standards in place, when it was built in 2005. Design standards are regularly updated to incorporate new learnings. The soon to be published amended Concrete Structures Standard will contain specific provisions that acknowledge the impact of beam elongation on frame buildings and how seating of pre-cast concrete floor units needs to be enhanced to capture current learnings.

 

Questions and Answers can be found below.

MBIE, the Institution of Professional Engineers New Zealand (IPENZ) and IPENZ technical societies have produced information for owners and building professionals responsible for assessing and designing multi-storey concrete moment resisting frame buildings with precast concrete floor systems that may be vulnerable to loss of floor support during an earthquake.

Framed buildings with precast concrete floor systems is available on the Building Performance website.

Recommendations

The Panel’s findings have made four recommendations:

Recommendation One:

  • MBIE has written to other councils – Hutt City, Upper Hutt and Porirua - about how the 14 November 2016 earthquake may also have affected similar buildings to Statistics House in their areas. This will enable them to contact the building owners so they can undertake damage assessments similar to those performed in the targeted building damage assessment programme undertaken by the Wellington City Council.
  • The New Zealand Structural Engineering Society and the New Zealand Society for Earthquake Engineering have issued guidance on how to assess damage to buildings which share the same design characteristics as Statistics House. This will ensure consistency amongst the assessments. It is up to engineers/owners and their insurers to determine how best to repair buildings.

 

Recommendation Two:

  • MBIE will be working closely with IPENZ and its technical societies to ensure the engineering profession is aware of the design issues with buildings similar to Statistics House.
  • MBIE, in collaboration with IPENZ technical societies, will develop comprehensive guidance to assist with assessing these types of buildings.

 

Recommendation Three:

  • MBIE has contacted Standards NZ, requesting that the Earthquake Actions Standard NZS1170.5 and Concrete Structures Standard NZS3101 standards committee meet to consider the findings from Statistics House investigation.
  • An amendment to Standard NZS1170.5 was published in September 2016 and the committee will need to consider what immediate modifications to the standard may be necessary to address findings from the Statistics House investigation
  • Standard NZS3101 is currently under review and Standards NZ is working towards getting this updated and released quickly and this can incorporate learnings from the Statistics House investigation.
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    Recommendation Four:

  • There is limited understanding of the impact of basin-edge effects and duration of earthquakes for New Zealand. MBIE will be commissioning further research to better understand basin-edge effects and the effects of duration. The research will involve international collaboration with countries that have cities affected by basin-edge effects such as Kobe and Los Angeles.