Tendon Control in Tall Structures

Slender structures that experience troublesome vibrations may be damped by either active or passive means. Active damping, which requires an external energy source, may be implemented by means of a feedback control mechanism composed of a motion-sensing device, an electrohydraulic servomechanism, and a pair of tendons to create a control torque at some point on the structure. The transfer characteristics of the controlled structure for displacement, velocity, and acceleration input are first examined, with special regard for stability limitations. Then the response amplitude curves are obtained, and finally the response of the controlled structure to random (white noise) excitation is studied. The results show that the stiffness of the tendons, the response time of the servomechanism, and the motion sensor characteristics play an important part in the control scheme. Significant reductions in response can be achieved with appropriate values for these three control parameters.