What does MBIE recognise as lateral stretch?
Is there a standard interpretation for this guidance? What is it?
Is that one interpretation to be used by all engineers when they calculate for a re-level or a rebuild?
Asked: 21 May 2015
Ministry of Business, Innovation, and Employment advises:
Lateral stretch in the guidance is translated into the damage to a foundation resulting from expansion of the ground under a residence during the earthquake sequence. It is described more fully in section 9 of the residential guidance and in figure 9.4 is shown to be on one axis: http://www.building.govt.nz/UserFiles/File/Publications/Building/Guidance-information/pdf/canterbury-technical-guidance-technical-information-part-b.pdf It is normally also evident from out of plumb end walls where the roof structure has remained intact.
Lateral stretch is normally measured in one direction and the 20 mm and 50 mm criteria referenced in the guidance are based on the sum of crack widths down one side of the building. Engineers will normally use the residential guidance and advice from the insurer on the homeowners’ insurance policy to determine the repair strategy for a property, the extent of lateral stretch may also indicate a need for further geotechnical investigation. There are a number of factors that will influence a recommendation for a re-level or a rebuild.