Professor Benson Shing of the University of Colorado Civil, Environmental, and Architectural Engineering Department and PhD Candidate Brian Rose are using ANCO's R-5 independent triaxial shake table to investigate unique servo-electric dampers for enhancing civil structure performance in large earthquakes. These devices consist of a DC motor/generator and ball screw arranged to produce an extension/compression strut. When elongated, the motor/generator produces a current flow which is then dissipated by a nonlinear electronic circuit. This circuit is designed to adjust the damping properties of the strut.

"In a typical moment resistant steel frame building," stated Mr. Rose, "the strut can be placed in a frame that introduces interstory damping. We are hoping to demonstrate that an efficient way to control structural vibration induced by wind and earthquake loads is to exploit the maximum damping capability of the device by using the maximum permissible damping coefficient and force under all circumstances. Based on this concept, a nonlinear control strategy similar to "bang-bang" control has been developed. This strategy, when used with our device, does not require any power supply to operate."

The concept is being demonstrated on a 1/4 scale model on the ANCO independent triaxial shake table. The project is sponsored by the National Science Foundation and involves the joint effort of researchers from Civil, Electrical, and Aerospace Engineering.