High-rise blocks tagged quake hazards

By SIMON COLLINS

An Auckland structural engineer says many pre-cast concrete high-rise blocks built in New Zealand since 1994 do not comply with sound engineering practice and would collapse in a big earthquake.

The engineer, John Scarry of Duffill Watts and King, has written a report documenting 26 examples of bad practices and describing one fault on a multi-storey building as "tantamount to conspiracy to commit mass murder".

He says the "leaky buildings" syndrome is "only the tip of the iceberg" of declining standards driven by competitive cost-cutting.

The Institution of Professional Engineers (Ipenz) has appointed a group to look into the allegations and has invited Mr Scarry to speak at its annual conference in Hamilton on Monday.

Ipenz chief executive Dr Andrew Cleland said: "The way to look at it is the size of the seismic event which it [a building] would withstand. We have made buildings where that limit is too low."

High-rise buildings would need to be assessed structurally through the same kind of exercise that the Government was funding for leaky homes.

"That is going to depend on the willingness to do that of the current owner, who may not be the builder. That cannot be taken for granted because it may drop their real estate values."

Cases cited by Mr Scarry include:

* A high-rise building where the core load-bearing walls were "essentially unattached to the floors" under horizontal earthquake forces because of openings for lifts and stairs.

* A 16-storey apartment building initially designed with "12 storeys of very stiff exterior and interior shear walls sitting on top of four storeys of sparse columns and very long span beams". Although this fault was detected in time to change it, Mr Scarry said any seismic engineer should have known that it was dangerous.

* A multi-storey hotel/apartment block where a subcontractor cut through stirrups that were holding beams in place in order to lay reinforcing concrete on top of them, then folded the stirrups down again and covered them up with wood. This was the case described as "tantamount to conspiracy to commit mass murder".

Mr Scarry said the examples were "symptomatic of virtually every project I have come across in the last six or so years". He said beam shear calculations for beams supporting precast flooring were "almost universally wrong and unconservative".

Engineers used more precast concrete structures than in other countries, he said. There was inadequate detailing to ensure that it performed as well as concrete cast on site.

The president of the Structural Engineering Society, Dr Barry Davidson, said New Zealanders should be concerned about Mr Scarry's report.

"Engineers who have read the report are concerned," he said.

"There would be some people who would say that the report is a little over-emotive, and perhaps making it a little worse than it really is.

"However, I think just about every structural engineer who I have spoken to would agree that they have seen some of these practices at some stage."

The rot widens

* The Building Act 1991 abolished the need for local councils to check building plans, and let engineers sign off their own "producer statements" certifying that buildings were structurally sound.

* Engineering fees were also deregulated, encouraging engineers to cut costs to win jobs.

* As a result, most engineers no longer supervise the actual construction of the buildings they design.

* The Scarry report says this has caused "widespread low standards of technical competence" and poor oversight of many high-rise buildings.

* The Government is now reviewing the Building Act because of the leaky homes crisis.