Quantitative analysis of factors influencing post-earthquake decisions on concrete buildings in Christchurch, New Zealand

The 2010-2011 Canterbury Earthquake Sequence resulted in unprecedented losses including 185 casualties, an estimated $NZ 40 billion cost of rebuild, and the demolition of 60% of reinforced concrete buildings in the Christchurch Central Business District (CBD). Intriguingly, demolition rate is unexpectedly high compared to the reported damages. This study thus sought to explore factors influencing the post-earthquake decisions on buildings (demolition or repair). Focusing the study on multi-storey reinforced concrete buildings in the Christchurch CBD, information on building characteristics, assessed post-earthquake damage, and post-earthquake decision (demolish or repair) for 223 buildings was collected. Data were obtained on approximately 88% of the 3-storey and higher reinforced concrete buildings within the CBD, or approximately 34% of all reinforced concrete buildings in the CBD. The study of descriptive statistics and trends of the database confirms that a significant portion of repairable buildings were demolished. Logistic regression models were developed based on the collected empirical data. From the significance testing, the assessed damage, occupancy type, heritage status, number of floors, and construction year were identified as variables influencing the building-demolition decision. Their effects on the post-earthquake decisions were approximated, and the resulting likelihood of building demolition was estimated for buildings with different attributes. From personal interviews with 9 building owners, 9 building developers and investors, 5 insurance sector representatives, and 4 local engineers and government authority personnel, it was learned that the local context, such as insurance policy and changes in local legislation, also played a significant role in the decision-making process. As the first quantitative study that explores the effects of factors on the post-earthquake building demolition decisions, the findings of this study indicates that the damage is not the only factor affecting the post-earthquake decisions on buildings. Incorporation of all influential factors in the probability-of-demolition function would provide better means of estimating expected total loss by considering decision outcome scenarios and associated costs. This would benefit the decision makers with comprehensive and valuable information concerning seismic risk management and strategy. Limitations on this study are discussed and similar studies are suggested reflecting the locality of different communities with seismic risk.Applied Science, Faculty ofCivil Engineering, Department ofGraduat