RAVENSCAR HOUSE, CHRISTCHURCH:
A BIOGRAPHY, DUE OUT NEXT YEAR
The earthquakes of 2010 and 2011 were a brutal reminder of the seismically active zone on which Christchurch had been built. Base isolators, designed to absorb seismic forces and so reduce the impact of an earthquake on a structure, were not a Christchurch City Council requirement but they had been shown not only to provide the greatest protection for people but also to get businesses up and running quickly after a seismic event and to better preserve a building’s contents. Basically a rubber-and-steel sandwich with a core of lead, they are designed to give flexibility, add strength and absorb shock, allowing a building to roll with the punches rather than jolt and judder. As such, says Peter Boardman, senior structural engineer with Auckland-based Structure Design, responsible for the engineering solution for damage control for the new Ravenscar House, they are a frequent criterion for the loans of precious objects and art works.17
The use of base isolators also met one of the declared goals of the Christchurch City Council, to rebuild a post-earthquake city ‘that will be stronger, smarter and more resilient to physical, social, and economic challenges.’18 Still, it was not common. A 2017 report co-authored by Greg MacRae at the University of Canterbury found, of 74 new buildings built in the CBD since the 2011 earthquake, only 14 per cent were base isolated. Rarer still was the use of base isolators in a residential building.19
Base isolation, explains Boardman, can be a big ask. It is building-specific, dependent on the geotechnical make-up of the site and the design, type and size of the building, and adds to the initial building costs. ‘It is gaining a lot more favour now but still it is mainly for large buildings – Ravenscar is unusual in that it is small and single storey but we were able to talk about the value of the contents and work it out from there.’20
The requirements of a home, museum and valuable art collection also demanded …..