Vulnerability assessment of Christchurch buildings in Canterbury earthquakes

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Uma, S.R.; Dhakal, R.P.; Nayyerloo, M. 2013 Vulnerability assessment of Christchurch buildings in Canterbury earthquakes. Lower Hutt, N.Z.: GNS Science. GNS Science report 2013/20 35 p.

Abstract: On 22nd February, 2011, Christchurch City experienced a direct hit from a destructive magnitude (Mw) 6.2 aftershock following the main event of magnitude 7.1 on the 4th September, 2010. Ground motions from the February event far exceeded the seismic design spectrum corresponding to 500 year return period which is used to design normal structures in New Zealand. This report provides a review of ground motion intensities from the September and the February events in relation to the intensities used in building design which helps to put the observed performance of the building stock into context. The report also assesses vulnerability of building stock in the Christchurch region through a probabilistic displacement-based approach under the impact of the February event to provide probabilistic estimates of damage distribution. The numerical study shows that the damage estimates are high for the February event compared to the code-based demands and expectedly more pronounced for older reinforced concrete frames. Lessons from the aftermath of the Christchurch earthquake are highlighted in terms of reflections on design practices, impact of economics on building damage status and possibly a need for fresh look at the design philosophy in New Zealand. (auth)