Wellington buildings need to be better than bare minimum, engineer says

Monday 8th May 2017

Wellington's buildings need to exceed the minimum standard set by the building code if the capital city wants to improve its resilience to a major earthquake, says California seismic safety commissioner and engineer Kit Miyamoto.

New Zealand's building code is a "simplified checklist" where the 100 percent new building standard (NBS) was the bare minimum that had to be met to save lives, but didn't go beyond that, Miyamoto told a group of Wellington building owners at last week's launch of a Deloitte economic analysis into the Kaikoura quake. What's more, in an earthquake about one-third of buildings will perform better than the standard, about one-third in line with expectations, and one-third less than the standard, he said.

"That’s just not good enough. Society asks much more than that," said Miyamoto, who's also chief executive at structural engineering firm Miyamoto International. "It doesn’t look into damage or lost time."

Deloitte conservatively estimated last year's Kaikoura quake was costing the Wellington economy $1.25 million a week in productivity losses with people rehoused in different buildings. Deloitte partner Linda Meade told the meeting there had been relatively slow progress in lifting the capital resilience to a catastrophic event, which would need more coordination between central and local governments, land owners and property developers.

Wellington City Council ordered a targeted assessment of 80 properties in the wake of the November quake, while central government separately investigated the performance of buildings that suffered major damage, including Statistics House.

The Deloitte report noted the inefficient approach to building repairs and the stretched engineering resources that delayed the assessments.

Miyamoto International pitches its performance-based engineering as a better alternative to the percentage-based code that people are more familiar with because it assesses where a new or existing building could get the most impact.

Miyamoto's New Zealand head David Weir told the audience that the percentage code wasn't bad, but that the capital should target more than the minimum standard.

"For Wellington, the seat of government, we need to be designing to a higher code than the minimum standard," Weir said. "What they’re doing is prescribed to the minimum code. The brief is always you’ve got to meet the code, then at lowest cost - that’s what engineers have been doing for a long time."

Deloitte said that if Wellington was hit by an earthquake similar to what levelled much of central Christchurch in 2011 it could slash the city's gross domestic product by 10 percent, amounting to $26 billion over the following 13 years.

Meanwhile, a Market Economics report commission for the Transport Ministry projected the Kaikoura quake will cost the Wellington region between $765 million and $3.76 billion in reconstruction expenses. The bulk of that is in non-residential building work, which is seen ranging between $712 million and $3.56 billion.

(BusinessDesk)

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