MBIE confirms a consistency problem in assessing earthquake-prone buildings

18 August 2015

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The government department shepherding proposed legislation on earthquake strengthening through Parliament confirms the assessment of existing buildings is problematic.

Ministry of Business (MBIE) chief engineer Mike Stannard says the aftermath of the Canterbury earthquakes has highlighted the difficulty of achieving consistent assessments of existing buildings.

“Following the quakes, there has been much greater demand to undertake assessments, resulting in more engineers carrying out assessments, some of whom will have been less experienced,” Mr Stannard says in a written reply to NBR Online’s questions.

“Assessment of existing buildings is actually much harder than designing new buildings,” he says,

Yesterday, NBR highlighted the case of a 20-year old single story retail building in Greymouth that was initially assessed at zero to 5% of the new building standard (NBS) and four subsequent assessments resulted in scores ranging from 28% through to 67% NBS.

“While anecdotally, the sector is telling us the amount of variation in assessment outcomes is reducing, there will always be some amount of variation, depending on the level of investigation carried out,” Mr Stannard says.

Detailed plans may be unavailable, the properties of building materials can be uncertain and invasive investigations, such as removing ceilings or concrete, may be impractical and expensive, he says.

“It’s also an area that requires skilled judgement, often of very old buildings.”

But MBIE is clear that steps need to be taken to support improved assessment practices, he says.

“Considerable effort is occurring with MBIE supporting the professional societies to improve assessment guidance.”

The Building (Earthquake-prone Buildings) Amendment Bill, currently being considered by a select committee, provides for MBIE to set the assessment methodology, including specifying the tools used to identify earthquake-prone buildings, Mr Stannard says.

“A major review of current assessment practice is under way to support the development of the new methodology. MBIE will be consulting on this methodology in due course,” he says.

MBIE is “investing in increased guidance in areas where judgement is required” and an up-to-date version of a publication from the New Zealand Society for Earthquake Engineering (NZSEE) is expected by early 2016.

MBIE is also supporting professional societies’ training of engineers through a series of seminars and workshops.

“Some training on assessing unreinforced masonry buildings has already taken place, while further training will be rolled out on a topic-by-topic basis, focusing on different types of buildings and materials, once the guidelines are published,” Mr Stannard says.

Source - NBR