Building code no match for earthquake

16:00, Feb 28 2011

The violence of shaking in the latest Christchurch earthquake could have been three times greater than the one-in-500 years event the New Zealand building code is designed around, say building experts.

The Department of Building and Housing said the vertical shaking in the central business district was both extreme and unusual. Early indications suggest it was much more violent than designed for in the building code standards, which are based on the kind of shaking expected to happen every 500 years.

Standards were last changed in 2008, when those for big buildings holding large numbers of people – especially hospitals or schools – were boosted to accommodate the kind of shaking that occurs roughly every 1000 years, it said.

Asked if building code regulations should be further strengthened in the wake of the devastation, a department spokeswoman said it would be several months before data was available on which to draw conclusions.

New Zealand requirements for earthquake design had been progressively upgraded since 1935. With some exceptions, old buildings performed poorly and new buildings came through well, especially given the extreme shaking.

"Liquefaction was again a factor in building failure for some newer buildings and work is required to gain a better understanding of the implications for the building code."


The Dominion Post