'New era' in quake-protection design

ALAN WOOD
Last updated 13:56 21/02/2013
Greg MacRae
STACY SQUIRES/Fairfax NZ
University of Canterbury structural engineer and associate professor Greg MacRae.

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Construction engineers visiting Christchurch for a steel conference were today told they would contribute with innovative and resilient systems to the central city rebuild.

The Steel Innovations 2013 conference, being held over two days, is the first conference to be held in the new Air Force Museum extension at Wigram, which has a considerable makeup from steel components.

Steel Construction New Zealand manager Alistair Fussell said the choice of Christchurch and the timing of the conference fitted with the second anniversary of the February 22 earthquake, which devastated the city and has led to large-scale demolitions of the central city.

Tomorrow would rightly be a day of reflection and remembrance in the city, Fussell said. An underlying theme of Steel Innovations 2013 was resilience.

''It's fair to say that resilience is without doubt a quality that has characterised the people of Christchurch and the wider Canterbury region over the last couple of years.'' he said.

''But resilience also speaks to the Christchurch build environment, and it's our responsibility as academics, as engineers, as steel industry players to learn from the Christchurch earthquakes, to ensure the buildings are built, or the rebuilt structures, are indeed resilient structures that indeed lead to a safe and resilient city.''

It has been estimated that about 80 per cent of the buildings in the core of the city have or will come down.

The conference speakers, from the United States, Taiwan, Australia and New Zealand, would talk about proven and emerging steel technologies, including developments in seismic resistant systems in steel, Fussell said.

''We expect to see some of these world-leading innovative systems, some of which are being developed here in New Zealand, some in Christchurch itself, will be used in the rebuild,'' he said.

''We look forward to those technologies being implemented.''

Christchurch Mayor Bob Parker told conference attendees that despite the damage in the city there were many examples, including pop-up bars and other entertainment venues, showing ''a tremendous creative energy has been unleashed in these places''.

There were many other examples of new adaptive uses for land and buildings, including retail areas that had become carparks and containers that had become retail spaces, that would lead on to the rebuild proper.

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Before the earthquakes Christchurch could have been included in the potentially ''doomed'' cities of about half a million people in size, seeing a flight of young people to larger urban areas, and an aging population.

On the other hand, the larger Auckland was growing by about half a million people a decade.

The $30 billion to $35b rebuild gave a chance for Christchurch to bring young people back.

''Yes we have to be the safest city on the planet but it has to be more than that,'' Parker said.

''I hope you are going to be part of that and I hope your legacy will inspire us, as you work with the people that will create the new form that will define this city.''

University of Canterbury structural engineer and associate professor Greg MacRae said that in the rebuild, those in the construction industry should consider ''low-damage construction'' including that involving steel solutions, as well as base-isolators such as those used at Christchurch Women's Hospital.

The more common use of base-isolators in Japan meant that the associated building costs were often cheaper than traditional building methods in that country. In New Zealand two consultants had said the cost of installing base-isolators was ''cost neutral'' or ''slightly more expensive''.

Up to this point, buildings in New Zealand were designed the same way as cars were designed, to protect the inhabitants, but at a huge economic cost to the infrastructure.

''When we design a car, we design it so when it has a significant crash the car is written off but the occupants can get out safely,'' MacRae said.

''If we have a significant earthquake we design our buildings so that the building is damaged and may need to come down, and the occupants can get out safely.

''The result of this philosophy we see in the Canterbury earthquakes. You can see the number of structures, many of which have required demolition ... the question is then can't we do better?

''The way we do better is having a different design philosophy.''

Other ''low damage construction'' methods included the use of supplemental damping and post tensioned beams.

- The Press

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