Building Damage, Death and Downtime Risk Attenuation in Earthquakes

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2012-07-16

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Whether it is for pre-event prevention and preparedness or for post-event response and recovery of a catastrophic earthquake, estimates of damage, death and downtime (3d) losses are needed by engineers, owners, and policy makers. In this research, a quantitative "scenario-based" risk analysis approach as developed to investigate the 3d losses for buildings. The "Redbook Building" is taken as the typical New Zealand construction exemplar and analyzed for the 22 February 2011 Christchurch Earthquake. Losses are presented in the form of attenuation curves that also include the associated uncertainties. The spatial distribution of 3d damages over the height of buildings is also considered. It is thus shown that it is possible to discriminate between losses that lead to building replacement versus less severe losses that require structures to be repaired.

The 3d loss results show that within the Christchurch city (17 km radial distance from the earthquake epicenter): (a) the expected physical damage loss ratio is about 50% of the property value; (b) the expected probability that someone is killed or seriously injured is about 4%; and (c) the expected downtime for the building being out of service is about 24 weeks. However, when considering various uncertainties, one can have 90% confidence that these loss estimations will be as high as: (a) complete loss (100% physical damage), implying structure has a great chance of collapse; (b) 8% possibility of fatality, implying deaths and significant injuries are likely; and (c) 1-year downtime due to post-event reconstruction demand surge. These informative results demonstrate that even though structures, such as the "Redbook Building", may have been well designed and constructed to contemporary standards, significant damage can still be expected and the downtime loss is particularly large. In order to solve this problem, new building structures should ideally be built stronger, include recentering attributes, and use Damage Avoidance Design (DAD) armoring connection details.

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