About New Zealand Standards related to earthquakes and buildings
Yes, seismic consideration is an important aspect of all New Zealand building design Standards.
The loading Standards which include seismic considerations, particularly NZS 1170 Part 5:2004 Earthquake actions – New Zealand assist in defining the loads for buildings.
NZS 1170 Part 5:2004 Earthquake actions – New Zealand is a Standard that has two core functions:
- to provide methods for structural engineers to determine earthquake loading levels and specifications
- to determine the seismic design loads for specific areas of New Zealand
Earthquake or seismic loading is one of the basic concepts of earthquake engineering which means application of an earthquake-generated movement to a structure. It happens at contact surfaces of a structure either with the ground, or with adjacent structures.
Design Standards for construction materials such as timber, steel, concrete, and earth-building are developed in alignment with loading Standards to guide design tolerances.
The attached timeline (see Appendix A) of Standards relating to determining earthquake loading shows that the process is evolutionary. Progressively over the past 75 years these Standards have been improved and revised as knowledge about earthquakes, and how to design buildings to resist them, has improved. The last revision was in 2004.
Standards New Zealand technical committees draw on international, regional, and national Standards, recent earthquake learnings, new technologies, and practices as part of the development process.
The following information has been received:
- IPENZ’s overview notes that:
'Earthquake records show that some buildings may have experienced shaking more than two times more intense than a new building would be currently designed for …'
- The Department of Building and Housing notes that:
'….early indications are that the earth shaking was probably much more violent than designed for in New Zealand’s Building Code, with vertical shaking that was both extreme and unusual.'
'The Building Code standards are based on the kind of shaking expected to happen about every 500 years, and experts are saying that the shaking that occurred in Christchurch’s central business district may have been as much a three times greater than this.'
We recognise the importance of taking learnings from the two Canterbury earthquakes, and now the major earthquake in Japan, as part of any review of the Standard. We will continue to work with leading researchers including GNS Science, the University of Auckland, the University of Canterbury BRANZ (Building Research Association of New Zealand) and other industry experts to consider what changes, if any, are required.