Resonance suppression through variable stiffness and damping mechanisms

This paper describes the modifications in the dynamic behavior of a building structure when devices with variable stiffness and damping are installed in parallel with a low-damping isolation system. The results of eigen-value analyses of linear-elastic structural models with varying degrees of isolation stiffness and damping direct the subsequent design of a semi-active device. A hydraulic semi-active actuator is designed to minimize an H-2 norm of the closed loop system. Details regarding the energy storage mechanisms of the device are are retained in the device model. The energy dissipation mechanisms are idealized to be viscous in nature. The actuator behaves essentially as a visco-elastic Maxwell element with a variable damping coefficient. The response time of the control-valve mechanism in this actuator is studied to reveal the relative benefits of a valve that is fast to open and a valve that is fast to close. Device parameters that result in a variable damping and variable stiffness properties are given. A model-independent, bang-bang, control rule is employed to illustrate the closed loop control system when variable damping and Variable stiffness embodiments are deployed. Rules governing the placement of device with this control rule are given when the device is primarily dissipative.