Bearing Up
Development
Extra floor space (click to enlarge)
A third of the weight is picked up at each level (click to enlarge).
COP Outcome development and evaluation
Having chosen this option SKM, with the help of Robinson Seismic and the Institute of Geological and Nuclear Sciences, analysed the likely response of the superstructure using records of Turkish, Mexican and American earthquakes similar to what could be expected from movement of the Wellington fault or a very large earthquake in the Wellington area.
The records were modified to allow for "near fault" effects, and used with 3-D computer-modelling of the structure to predict how the library would move every fraction of a second in the various earthquake records. Engineers then worked out how to eliminate or minimise the forces acting on structural members and the building's responses, with and without base isolation, working out a response envelope within which the building had to be kept. Without base-isolating bearings the building would not collapse, but might have to be rebuilt and damage would be extensive.
The design criteria specified that the building should withstand a Code design-level earthquake with a 450-year return period, remaining operable with only minor damage. Movement on the Wellington Fault with a mean return period of 600 years is likely to generate a magnitude 7.3 earthquake on the Richter scale. Mr Clark says such an earthquake would cause "quite a bit" of damage to the building particularly to the lift shafts and block walls, but the rest of it "should be quite operable".
