UC experts asks what if we could minimise financial loss from earthquakes?

The public did not expect to bear more than $30billion in loss from the Christchurch earthquakes having been reminded regularly that New Zealand was leading the world in earthquake-resistant design, a University of Canterbury engineering specialist said today.

Rajesh Dhakal, UC’s associate professor of structural and earthquake engineering, said it was clear that the objectives of seismic design stipulated in the current codes did not meet public expectation. He will talk about reducing financial loss from earthquakes at a public lecture on the UC campus tomorrow night.

Apart from the collapse of the CTV and PGC buildings and the subsequent loss of lives which was regrettable, Christchurch’s modern building stock in general stood up to a series of earthquakes which generated ground movement much stronger than what the buildings were designed for, he said.

``The performance overall was arguably better than what the engineers and designers might have expected. But the losses from the earthquakes have been heavy when looking at dollars, downtime, and death/injury. All three forms of loss originate from damage.

``However, damage in an earthquake will not just be constrained to the load bearing structural components of a building. As we observed, even the secondary non-structural building components (such as ceilings, partitions, facades, windows parapets, chimneys, canopies) and contents will be damaged in an earthquake and these can result in all three forms of loss.

``Hence, in addition to employing a low-damage structural system in a building, we also need to follow damage resistant principles in designing and installing the non-structural components (and contents) to achieve a low-loss building system.’’

Associate professor Dhakal said some of the emerging building technologies look very promising. Specially, base isolation has been proven to reduce both inter-storey drifts and floor accelerations, thereby reducing the likely damage to the structural and non-structural components of a building and its contents.

Consequently, a base isolated building will result in substantially reduced loss due to damage, downtime and death/injury. However, such technologies require additional initial cost. Real estate and insurance industries would have to play an active role in creating incentives for builders and owners to adopt loss-minimising technologies, he said.  

``We have to modify the existing design approach so that it explicitly aims to minimise financial loss in addition to life safety. This, combined with an integrated soil-foundation-superstructure system capacity design approach, will result in cost effective building systems in future.’’