From Ductility to Repairability: Evolution of Building Design After the Christchurch Earthquake

New Zealand and many other countries around the world adopted ductility-based design concepts in the late 1970s and early 1980s. The adoption of these design concepts are likely the single most important advancement in our design philosophy in terms of protecting life safety in future earthquakes. Ductility, however, cannot be achieved without damage to the structure and its contents. Recent earthquakes have openly challenged the engineering community as to whether our focus on ductility has delivered what society intrinsically expects from its buildings during and after strong earthquakes. Recognizing that building design is best driven by observations from real earthquakes, we will use the 2011 Christchurch Earthquake as a case study to explore if it is time for another fundamental shift in our approach to building design; from ductility to repairability.
How we design and construct buildings will clearly influence building performance in future earthquakes, which will in turn influence outcomes for occupants (injuries and deaths), as well as for the buildings themselves (demolition, repairs, abandonment). But it is the economic, environmental and social impacts resulting (in part) from these human and building outcomes which leave a lasting impression on our communities. Managing these impacts from future earthquakes should be the driver behind future changes to how we design buildings. Eleven years after the Christchurch earthquake we are now in a better position to appreciate such impacts including business losses, insurance costs and delays, environmental impacts, urban blight, and wellbeing. We will review some of these impacts and reconsider if our building design targets are suitable for managing these impacts in future earthquakes. We argue a need to change our focus from just life-safety to serviceability in frequent earthquakes and repairability in design level ground motions. Component deformation limits for concrete buildings which enable structural repair without loss of structural safety will be discussed and the repairability of current structural designs will be assessed.