Housing performance and extreme events – lessons learnt from Cyclone Tracy for a more resilient Darwin

On Christmas Day 1974, Tropical Cyclone Tracy hit Darwin resulting in 66 deaths. The devastating event also left more than 650 people injured and more than 60 per cent of houses damaged beyond repair. This led to large-scale evacuation of Darwin and the reconstruction of the city. This event highlighted the potential impact extreme weather events can have on built infrastructure. Past experiences in design and construction cannot be relied upon to withstand the loads associated with rare and extreme wind pressures in an event such as Tracy.

As we approach the 50th anniversary of Tropical Cyclone Tracy we reflect on the research led by former CSIRO employees Dr Bob Leicester and Dr Greg Reardon who undertook a damage survey of more than 2,700 buildings in the immediate aftermath of the Cyclone. Their research undertook a statistical analysis of the estimated peak wind speed and the building damage incurred. Key findings from their research included:

• For rare events such as cyclones, the risk of structural collapse was not due primarily to material properties, rather it was due to construction errors.
• Buildings and structures designed according to engineering principles were more likely  to withstand the extreme loads. 
• An increase from minor to major building damage involved only small increase in wind velocities, as any structural failure increases potential for further failures in other modes (e.g. loss of windows on windward side increases internal pressure on roof).
• Post Cyclone Tracy engineered construction has been incorporated in many building standards in Australia.

More information on their research is available here (see section: Wind and Cyclones) or see Further reading.

The Darwin Living Lab recently presented Dr Bob Leicester’s research as part of the 50th Anniversary Commemoration events. If you would like a copy of the slides presented, please email: DarwinLivingLab@csiro.au

Image source: Bob Leicester and Greg Reardon, CSIRO

Further Reading

• Leicester, R. H., and G. F. Reardon. 1976. “A Statistical Analysis of the Structural Damage by Cyclone Tracy.” Civil Engineering Transactions, Institution of Engineers Australia CE18: 50–54. Barton, ACT, Australia.
• Leicester, R. H., and F. D. Beresford. 1978. “The Resistance of Australian Housing to Wind Forces” CSIRO Division of Building Research. Melbourne, VIC, Australia.
• Leicester, R. H., C. T. J. Bubb, C. Dorman, and F. D. Beresford, 1979. “An Assessment of Potential Cyclone Damage to Dwellings in Australia.” Proceedings of the 5th International Conference on Wind Engineering July 8–14, 1979. Fort Collins, CO, USA.
• Leicester, R. H., and G. Reardon. 2010. “Impact Statistics of Tracy and an Opportunity Missed.” Australian Meteorological and Oceanographic Journal 60: 207–212. doi:10.22499/2.6003.009.