EarthquakesSimulations help in studying earthquake dampers for structures

Simulation of earthquake on nine story building using MR dampers // Source: gsn207nees via youtube.com

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.

A Purdue University release reports that 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.

Research led by Dyke and doctoral students Gaby Ou and Ali Ozdagli has now shown real-time hybrid simulations are reliable in studying the dampers. The research is affiliated with the National Science Foundation’s George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES), a shared network of laboratories based at Purdue.

Dyke and her students are working with researchers at the Harbin Institute of Technology in China, home to one of only a few large-scale shake-table facilities in the world.

Findings will be discussed during the NEES Quake Summit 2013 on 7-8 August in Reno, Nevada. A research paper also was presented in May during a meeting in Italy related to a consortium called SERIES (Seismic Engineering Research Infrastructures for European Synergies). The paper was authored by Ou, Dyke, Ozdagli, and researchers Bin Wu and Bo Li from the Harbin Institute.

“The results indicate that the real-time hybrid simulation concept can be considered as a reliable and efficient testing method,” Ou said.

The simulations are referred to as hybrid because they combine computational models with data from physical tests.

“You have physical models and computational models being combined for one test,” Dyke said.

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.

“Sometimes real-time testing is necessary, and that’s where we focus our efforts,”