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Australian Researchers Simulate Powerful Earthquakes

Phil Mercer

Researchers in Australia have simulated the impact of strong earthquakes on a 15-story model building to help improve design in seismically-sensitive regions around the world.  The experiment has tested the response of office and apartment blocks built on soft clay to violent seismic shocks, including the quake that devastated a Japanese city in the mid 1990s.  Scientists say it is the first time a trial of this size and detail has been conducted anywhere.

For a few seconds the earthquake that struck the Japanese city of Kobe in 1995 is re-created in a laboratory at the University of Technology Sydney.

A model 15-story building made of steel is subjected to the kind of trauma that killed thousands of people.  Each floor is carefully monitored to see how they shift and buckle under the strain.

Three other significant quakes have also been replicated, including the El Centro earthquake that struck California in 1940 and another in Hachinohe, Japan in 1968.

The aim of the experiment is to test the response to earthquakes of office and apartment blocks built on soft soil, which researchers say can amplify seismic waves.

Professor Bijan Samali says it is the only experiment of its kind to investigate how soil reacts under such intense pressure.

"Soft soil you can think of it as a layer of jelly, [a] slab of jelly on a table," said Samali.  "If you push the table a little bit, the top of [the] jelly moves a lot more than the bottom of the jelly, isn't it?  By having a building on top of a jelly it will experience a lot more displacement and a lot more forces.  So, if that phenomenon is not taken into account in [the] design stage you might end up with a structure that would not survive, so this is certainly a safety issue."

Engineers in Australia are using what is called a "shake table," where tons of soil and a replica tower block oscillate above a sophisticated hydraulic system.

It is hoped the earthquake simulator will improve the resilience of buildings in seismically active regions where homes and skyscrapers are constructed on soft clay and marshland.

The research team says that in 2011, 20 earthquakes with magnitude seven or above occurred around the world causing more than 17,000 deaths.  It is likely that some of the fatalities were in high-rise buildings built on soft soil.

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