Gravity-Actuator System for Control of Civil Structures

Abstract

Many of the active devices currently being researched for seismic structural control applications are highly energy intensive. This presents a serious concern for active control since adequate energy sources may not be available during an earthquake. To alleviate this concern, an innovative gravity-actuator control system is proposed herein. This control system minimizes the external energy demand by using the reserve kinetic energy stored in suspended active masses to generate lateral forces for control. An idealized model of the gravity-actuator system is analyzed in detail, and equations governing the dynamic response of this model are derived. An algorithm that uses short-duration force pulses to attenuate the structural response is developed for operation of this control system. Numerical examples considering the response of a seismically excited model structure are presented to assess the performance of the control system and the pulse-control algorithm. Results demonstrate that the gravity-actuator control system is capable of significantly reducing the lateral vibrations of the structure, thereby indicating the proposed control concept to be worthy of continued study.