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28 June 2002 Real-time seismic damping and frequency control of steel structures using nitinol wire
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Thirty years ago, automotive engineers perfected real-time damping for vehicle suspension systems prior to hitting bumps in the road. In the near future, architects and structural engineers may be able to use the same philosophy for tuning structures to withstand earthquakes as their waves impinge on the structure. Coupled with seismic monitors and a reliable communications systems such as California's TriNet real-time seismic monitoring system which can relay specific ground motions to buildings, we can expect that-we will be able to tune building frames to reduce both motion and damage in an economic manner. Most materials respond to heat by expanding in volume. Nitinol is a shape memory alloy (SMA) that has the peculiar quality ofcontracting when heated. By variably heating a system ofnitinol wires designed within a building structure, the frequency response ofthe structure, torsion and percent ofcritical damping could be altered as the structure experiences an earthquake. Nitinol is a nickel-titanium-based metal that has seen use in robotics for return control that resembles the bioenergetics ofmuscles and tendons. Small electrical currents can be placed into the nitinol where the resulting resistance causes rapid heating and consequent reduction in volume. By lacing steel buildings with a series ofnitinol wires in cross directions and coupling them with both an energy source and communications receiving systems from TriNet, the response ofthe building structure can be altered. This could improve damping ratios with respect to any particular earthquake in a similar fashion to forward looking automotive suspension systems. This paper shows examples by using building models.
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Gary L. McGavin and Greg Guerin "Real-time seismic damping and frequency control of steel structures using nitinol wire", Proc. SPIE 4696, Smart Structures and Materials 2002: Smart Systems for Bridges, Structures, and Highways, (28 June 2002);

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