1493782715872 - Engineers welcome new seismic assessment rules

Engineers welcome new seismic assessment rules

Some property owners and managers have been at their wit’s end over conflicting engineering reports about the safety of their buildings in and earthquake.

A new assessment standard will take effect in July and was discussed by more than 500 engineers at the New Zealand Society of Earthquake Engineering(NZSEE)’s recent annual conference in Wellington.

Wellington buildings have had wildly differing assessments and the Property Council chief executive Conal Townsend said it could wipe millions of dollars from the value of properties. 

The problem came into sharp focus during the 14,000 earthquakes which hit Canterbury after September 2010 and throughout 2011.

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The first assessments were cursory and often horribly wrong.

For example, the CTV building which killed 115 people out of the total toll of 185 when it collapsed in the strongest February 22, 2011earthquake, had been assessed as sound in spite of many warnings from tenants and staff.

Conversely, other buildings were closed but stood up well in ensuing months.

Construction magnate Buzz March recalled some buildings which “almost fell down at the first swing of the wrecker’s ball”.

But one of the last major Christchurch demolitions – the ex-BNZ building in Cathedral Square – has arguably been one of the longest and toughest demolition jobs in the city because of the strength of the building.

NZSEE President Peter Smith said engineers were learning lessons from how buildings performed in the complex Kaikoura earthquake.

“When we design a building, we’ve always focused on protecting lives first and foremost. But now, we’re also asking whether buildings need to be more resilient, so that they experience less damage and can be more quickly reoccupied after an earthquake.

“There’s a trade off that developers and building owners need to consider, between investing in resilience and suffering economic loss if a building can’t be used for some time after an earthquake,” Smith said.

Structural Engineering Society spokesperson Paul Campbell said engineers were looking forward to new earthquake-prone buildings legislation.

“One of the things this legislation does is introduce more prescriptive guidelines for seismic assessments of buildings, which will make assessments more consistent.

“While there may be differences of opinion between engineers, they need to be in the same ballpark. The new guidelines will help make sure building owners can compare apples with apples.”

IPENZ (Institution of Professional Engineers NZ) chief executive Susan Freeman-Greene said Thursday May 4 is 177 days after the Kaikoura earthquake and a sobering reminder of the seismic risk posed by earthquake-prone buildings.

“Christchurch’s devastating February 2011 aftershock came 177 days after the first Canterbury earthquake.

“Because the Kaikoura earthquake on November 14 mostly affected mid-height buildings, it’s been easy for Wellingtonians to feel less concerned about shorter, stiffer earthquake-prone buildings.

“But Thursday forcibly reminds us of the lives lost when facades collapsed in the Christchurch February earthquake. 

“Thirty-nine people were killed and more than 100 people injured as a result of masonry falling onto footpaths and roads,” she said.

“Engineers are extremely supportive of the Government’s move to compel building owners to secure facades, which will save lives in a large earthquake centred closer to Wellington.

“If an engineer is aware of previous assessments that differ significantly from the one they have produced, then they should engage with the authors of those assessments and try to reach agreement,” Freeman-Greene said.

The guidelines are included in the Building (Earthquake-prone Buildings) Amendment Act 2016 which comes into force in July.

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