Lessons for loss assessment from the Canterbury earthquakes: a 22-storey building

Abstract

By comparing damage and loss predictions with those observed for a 22-storey steel building with eccentrically based frames (EBF) that underwent the Canterbury earthquakes, this paper gauges the performance and explores the benefits of applying the PEER performance-based earthquake engineering assessment procedure. The study shows that steel EBF repair costs are significantly affected by the work required to remove and reinstate non-structural elements in order to access the steel structure. It is therefore concluded that the location of non-structural elements relative to structural elements should be considered in the seismic design of new buildings and within loss assessment procedures. Two retrofit and/or rehabilitation options are considered for the building; improving the deformation capacity of drywall partitions, and re-detailing the exterior cladding connections to better accommodate structural deformations. The findings show that, for the specific building, improving the drywall partitions should lead to a reduction in expected annual losses whereas the use of improved detailing for the precast concrete cladding would not. This suggests a general strategy for cost-effective decisions might be to focus on increasing the performance of the most vulnerable components (plasterboard partition walls, in this case). An examination of the potential effects of aftershocks to the selection of cost-effective options adds support to this conclusion. Aftershocks are found to increase the predicted losses by around 10%, emphasizing the need to consider aftershocks when assessing expected annual losses due to earthquakes.