		2006 NZSEE Conference
	Abstracts

Keynote Address Learning from Hawke's Bay 1931 Earthquake Performance Assessment and Retrofit Decision Making for Risk Mitigation Behaviour of Walls and Piers Understanding Reinforced Concrete Behaviour Modelling Earthquake Performance Earthquake Performance Poster Papers Design and Development

From Brittle to Ductile: 75 Years of Seismic Design in New Zealand

Les Megget

“Earthquake-resistant design does not rest on any clearly defined basis; many fundamentals are obscure.”

“As it is generally held that destructive seismic vibrations have, as a rule, periods of from 1 to 2 seconds, it is advisable for the natural period of a building to be less than 1 second. If it were above the 2 second limit, we should have a decidedly flexible structure, large movements, likelihood of damage to various rigid elements, risk of panic and other ill effects”

From “Structural Design of Earthquake Resistant Buildings” by Irwin Crookes, 1940.

This address 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 ‘quake 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 the 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!

Paper P01: [Read]