Structural integrity of Wellington buildings raising serious questions


Since the earthquake on the morning of Monday 14 November, some serious questions have been raised about the structural integrity of buildings in the central business district of Wellington. The damage has been varied, but has caused the closure of a number of buildings as diverse as the Asteron Centre, which houses the Inland Revenue Department and the Fijian High Commission. Some of the buildings that have been evacuated are stately older buildings built before a building code existed and possibly not compliant. Others are new buildings that were constructed as recently as 2007-2010 when not only did building codes exist but they would be quite stringent.

Unfortunately there are some serious questions that have to be addressed. One of them is why 1/3 of the building code strength is considered acceptable in a country which has seismic activity comparable to California. Another would be, unless these are isolated incidents why are stairwells failing in new/near new buildings? But an even bigger one would be, whether or not short cuts are being taken in the design and construction of buildings and if so, what are we going to do about it?

This is cause for concern. In an earthquake a building’s primary function is to withstand the shaking and then let out its occupants safely. To that end the building code exists for a very good reason. In Christchurch several buildings suffered stairwell failure that prevented them being safely evacuated via the stairs on 22 February 2011. One of them was the Forsyth-Barr building, which otherwise came through structurally sound and is now being eyed up as a hotel. This particular building trapped numerous people in its upper floors who had to be lowered to floors where the stairwells were still intact, or to ground level.

115 people died in the C.T.V. building and another 18 in the P.G.C on 22 February 2011. The P.G.C. building was built to the design standard in 1963, but found in 1997 to be below the then building code with regards to seismic events. Damage from the aftershocks between 04 September 2010 and 22 February 2011 did not significantly worsen the condition of the building, which collapsed because the shaking was many times stronger than its capacity to resist.

The Canterbury Television building had major design and construction flaws. Although the building was not initially damaged on 04 September 2010, it suffered sufficient damage in the 26 December 2010 aftershock that the building should have been evacuated. In January 2011 following another strong aftershock tenants began to become concerned about cracks appearing in the building. The architect who designed the building was not experienced in designing multi-story buildings. Its construction was not properly supervised. When completed it was a building whose seismic load bearing was significantly less than the 1986 standard to which it should have been built. In releasing its findings the Royal Commission of Inquiry into the Christchurch earthquake and the performance of the buildings it was found that the Christchurch City Council should not have issued the building permit

Christchurch learnt this the hard way. That does not mean Wellington should too.

 

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