Review of observed Christchurch damage data and performance assessment of buildings in Christchurch

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Uma, S.R.; Lin, S.-L.; Buxton, R. 2014 Review of observed Christchurch damage data and performance assessment of buildings in Christchurch. Lower Hutt, N.Z.: GNS Science. GNS Science report 2014/29 22 p.

Abstract: The lessons from the aftermath of earthquake ground motions and from the observed damage to land and built environment provide opportunities to learn and improve our understanding of earthquake performance and to make changes in policy and practice. Failures and damage to built-environments due to earthquakes, especially recent events, have stimulated engineering professionals to revisit existing policies and practices to make improvements wherever necessary. In this regard, the Christchurch earthquake events and the observed damage in buildings have provided a unique opportunity for professionals and policy makers to evaluate the current practices and to incorporate changes. Further, the New Zealand Building Code adopts a performance-based approach and sets the objectives and goals related to functional and performance requirements of a building. With the Christchurch experience, understanding performance of buildings is of paramount importance. The present study endeavours to derive generic understanding on the performance of Christchurch building stock in relation to the ground motion demand. This is done through: (i) careful scrutiny of the observed damage survey data obtained from the Christchurch City Council; and (ii) establishing the ground motion demands at building sites. The damage survey forms as used in ‘Rapid Assessments’ after every significant shaking, provide information on overall building damage ratio and this is used as a performance indicator in this study. However, it is realised that building performance in broader terms can include damage to the buildings, loss of functionality, repair time and casualties. Further, an attempt has been made to relate the building damage ratios to the tolerable impact levels as referred within the Building Code (in revision) through a mapping scheme in order to understand the distribution of buildings with a range of impact levels sustained. The findings from the present study have indicated that the building performance was satisfactory from the Building Code point of view. However, this statement has to be carefully interpreted with a number of caveats highlighted within this report. (auth)