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Research at Rensselaer

CEES lab mimics stress

Posted on October 19, 2011 in Uncategorized by David Hodson, Senior Reporter

Research is going strong at the Institute’s Center for Earthquake Engineering Simulation headed up by Professor Ricardo Dobry and Associate Professor Tarek Abdoun. The CEES at RPI practices what is called physical modeling, where a small scale model of a given piece of some kind of infrastructure, for example a dam, levee, tunnel, or building, is created and tested in the center’s geotechnical centrifuge lab. This lab functions in a similar way to a wind tunnel, where a small scale model of a complicated system is put under stress in order to draw data from it that will help inform design processes on a greater scale.

The ability to test small scale models under real stress is incredibly useful for tests where the goal is to put a given sample or structure under stress to the point of failure in order to better analyze it. It is also useful for things like blast tests, where the point of the test is to find a structure’s resistance to an explosive blast, and attempt to enhance structure through the findings of such a test, as Abdoun said, “If you are worried about terrorist attacks and so on and you want to enhance the design of some of your previous structures you can build models of it and test it under blasts and see how it would perform. No one would allow you to do that in real life.”

Also according to Abdoun this system is good for modeling complex systems because it is a very economical testing method in addition to working on the testing of models that are too complex to be effectively tested via computer based methods.

The CEES group and its geotechnical centrifuge lab have done a lot of work in the past on many projects related to different public infrastructure works, including testing on the New Orleans levee systems. Their projects discovered flaws in the designs of the levees and allowed for the redesign of the levee system on both a physical level and in the numerical and computer models associated with the analysis of the levee system. Since that redesign of the geotechnical centrifuge lab has also been used to analyze the newer models and structure proposed for the levees guarding New Orleans.

CEES has also worked with the Department of Homeland Security regarding man-made hazards. This cooperation has resulted in the small scale testing of dams, spillways, and levees for how they can currently absorb damage from man-made sources and how they could be repaired or modified to be better absorb stress from these sources. In addition, it partners with many governmental and non-governmental groups for general stress analysis of these kinds of structures in addition to more common structures like buildings and roadways with the goal of failure prediction and prevention due to natural stresses and processes.

The centrifuge that the lab revolves around is one of three such devices in the world, with an arm radius of approximately 3 meters. The upper speed limit that the centrifuge runs at results in 160 times the force of gravity incident on the experimental surface of the centrifuge, which is useful for modeling systems because the bottom of a 1 foot tall sample under 160 gravities is under the same amount of force as it would be if that point were actually under 160 feet of dirt. The centrifuge lab actually has a special apparatus specific for earthquake testing; it is a shake table designed to be fit onto the centrifuge and run while the centrifuge is spinning.