Researchers have demonstrated the reliability and efficiency of "real-time hybrid simulation" for testing a type of powerful damping system that might be installed in buildings and bridges to reduce structural damage and injuries during earthquakes.

The magnetorheological-fluid dampers are shock-absorbing devices containing a liquid that becomes far more viscous when a magnetic field is applied.

"It normally feels like a thick fluid, but when you apply a magnetic field it transforms into a peanut-butter consistency, which makes it generate larger forces when pushed through a small orifice," said Shirley Dyke, a professor of mechanical engineering and civil engineering at Purdue University.

This dramatic increase in viscosity enables the devices to exert powerful forces and to modify a building's stiffness in response to motion during an earthquake. The magnetorheological-fluid dampers, or MR dampers, have seen limited commercial use and are not yet being used routinely in structures.

Researchers are able to perform structural tests at slow speed, but testing in real-time – or the actual speed of an earthquake – sheds new light on how the MR dampers perform in structures. The real-time ability has only recently become feasible due to technological advances in computing.

The simulations can be performed in conjunction with research using full-scale building tests. However, there are very few large-scale facilities in the world, and the testing is time-consuming and expensive. To prove the reliability of the approach the researchers are comparing pure computational models, pure physical shake-table tests and then the real-time hybrid simulation. Research results from this three-way comparison are demonstrating that the hybrid simulations are accurate.

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