Base Isolation

width=250Base isolator bearings were pioneered in New Zealand by Dr Bill Robinson during the 1970s, and have enjoyed widespread adoption as a damage resistant seismic design solution for new and retro-fitted concrete buildings.

Base isolation works by separating (“isolating”) the structure from the ground, and therefore the lateral forces of an earthquake. There are two types of base isolation – elastomeric and sliding – both of which are designed to take the weight of the building and let the foundations move sideways during an earthquake.

Flexible elastomeric bearings consist of layers of bonded rubber and steel with a central lead core. The lead core softens when under pressure absorbing energy that would otherwise be transferred to the building. With a sliding system there is no energy absorption, just deflection through the bearing. With both types of base isolation, building movement during an earthquake is greatly reduced, meaning less risk of damage or injury.

Opened in 1982, the William Clayton building in Wellington uses about 80 lead rubber bearings, while Te Papa, opened in 1998, has 152 bearings. During the early 1990s the New Zealand House of Representatives, also in Wellington, was retro-fitted with 417 isolator bearings.


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“We must keep pushing for the best technology in reinforced concrete design and construction, and the best concrete material amongst a growing number of options that reflect advances in engineering.”

STEFANO PAMPANIN
UNIVERSITY OF CANTERBURY


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Selected Resources

Title: Base isolation for increased earthquake resistance of buildings
Author: Skinner, R.I. & McVerry, G.H.
Source: Bulletin of the New Zealand Earthquake Society of Earthquake Engineering. December 1978, 11 (4): 93-101.

Title: Seismic Forces in Base-Isolated Masonry Structures
Author: M.J.N. Priestley, R.L. Crosbie & A.J. Carr
Source: Bulletin of the New Zealand Society for Earthquake Engineering (1977), Jun 1977; v.10 n.2:p.55-68

Title: Base Isolation - An Historical Development, and the Influence of Higher Mode Responses
Author: D.M. Lee & I.C. Mediand.
Source: Bulletin of the New Zealand Society for Earthquake Engineering (1978), Dec 1978; v.11 n.4:p.219-233

Title: Estimation of base isolated structure responses
Author: Lee, D.M. & Medland, I.C
Source: Bulletin of the New Zealand Earthquake Society of Earthquake Engineering. December 1978, 11 (4): 234-244.

Title: A tenacious base isolation system using round steel bars
Author: Tyler, R.G.
Source: Bulletin of the New Zealand Earthquake Society of Earthquake Engineering. December 1978, 11 (4): 273-281.

Title: Recommendations for the design and construction of base isolated structures
Author: Blakeley, R.W.G., Charleson, A.W., Hitchcock, H.C., Megget, L.M., Priestley, M.J.N., Sharpe, R.D. & Skinner, R.I.
Source: Bulletin of the New Zealand Earthquake Society of Earthquake Engineering. June 1979, 12 (2): 136-157.

Title: A base-isolation design using spherically-ended rollers and telescopic shock absorbers
Author: L.T. Pham
Source: Bulletin of the New Zealand Society for Earthquake Engineering (1988), Jun 1988; v.21 n.2:p.135-139

Title: Base isolation of an existing 10-storey building to enhance earthquake resistance
Author: W.D. Clark & J.E. Mason
Source: 2004 NZSEE Conference

Title: A Simple Approach to Real-Time Fault Detection and Diagnosis in Base-Isolation Systems
Author: M. Nayyerloo, L. Acho, J. Rodellar, J.G. Chase & X. Chen
Source: Proceedings of the Ninth Pacific Conference on Earthquake Engineering: Building an Earthquake-Resilient Society, 14-16 April, 2011, Auckland, New Zealand

Title: Costs of Base-isolation and Earthquake Insurance in New Zealand
Author: A.W. Charleson & N.J. Allaf
Source: 2012 NZSEE Conference

Title: Performance Objectives for Low Damage Seismic Design of Buildings
Author: J. Hare, S. Oliver & B. Galloway
Source: 2012 NZSEE Conference

Title: Using Seismic Isolation and Energy Dissipation to Create Earthquake-Resilient Buildings
Author: R.L. Mayes, A.G. Brown & D. Pietra
Source: 2012 NZSEE Conference