Bridges to cope with shocks

Press, 12 November 1977, Page 11

Bridges to cope with shocks

PA Wellington Shock absorber’s, which can withstand earthquakes of at least magnitude 7 on the Richter scale, are being installed for the first time in New Zealand in two Wellington bridges. According to the inventor of the absorbers, which are officially known as lead extrusion dampers, it is the first time they have been used anywhere in the world. Dr Bill Robinson is the head of the physics division of the Physics and Engineering Laboratory at the Department of Scientific and Industrial Research and has spent about two years developing the dampers. Six dampers were installed in the Aurora Terrace overbridge on Wellington’s urban motorway and another six are being installed at the Bolton Street overbridge. The dampers work like a vehicle shock absorber, but instead of using oil they

use lead. There are pistons, connected by a tie rod, inside. Between the pistons and tie rod is high purity lead which is extruded past a restricted part of the cylinder when forces are applied to bridges.

The bridges are mounted on glide bearings which allow the bridges to move horizontally. The damper's also stop the bridge from moving during the braking of heavy vehicles going over the bridge. Dr Robinson said the dampers had been tested 20 times before installation, for an earthquake magnitude of 7 “and they should withstand even, stronger quakes.’’ Apart from in this country, where the dampers are now being made commercially by an Auckland firm, the New Zealand Government has taken out patents in the United States, the United Kingdom, Australia, and Japan. D.S.I.R. investigations are also continuing into a similar type of shock absorber for use in buildings. However, Dr Robinson said there was a considerable amount of work still to be done in this area.

Tennis.—Renee Richards, an American transsexual, won through to the final of the River Plate women’s international tennis championships in Buenos Aires when she defeated Viviana Gonzalez Loccicero. of Argentina. 6-0, 7-6. She will meet Ivana Madruga (Argentina).