From brittle to ductile

Abstract

This paper traces the development of seismic structural design in New Zealand since the 1931 Hawke’s Bay Earthquake, with emphasis on reinforced concrete buildings. From the mainly rigid and brittle unreinforced masonry structures which behaved so poorly in the 1931 earthquake through the development of flexible ductile seismic design and base (seismic) isolation of the 60’s to 80’s to today where the structural engineer is expected to design and construct a building which will not only remain standing with little damage but will be operational a short time after the major earthquake. In some ways the structural design aims and objectives have turned full circle in the intervening 75 years. We have gone from brittle rigid structures through a period where flexibility was paramount to now where flexibility is limited and greater lateral stiffnesses are required, but with ductile elements in the structure. This paper traces the efforts of New Zealand’s pre-eminent structural engineers and scientists to make seismic design techniques world leading. In most facets they have been successful (in my view) but as I will say more than once, only time will tell!