Active Control of Inelastic Structures

Abstract

This work presents a methodology for the shape control of structures undergoing inelastic deformations through the use of an active pulse/force system. Large flexible structures such as tall buildings, long bridges, and offshore platforms tend to develop large deformations under the action of intense dynamic loads such as wind, waves, or earthquakes. Unless these deformations are controlled in some fashion, the structure will sustain extensive damage that may lead to total collapse. One possible solution to this problem is to apply external forces to the structure through cables, air jets, or other devices in order to assure that the deformations are kept below the limits set for serviceability at all times. The methodology presented herein is based on an active control algorithm derived from standard numerical integration methods that uses corrective pulses or forces to limit the response of a structure that has already entered the inelastic range. Material nonlinearities are accounted for by use of standard incremental/iterative procedures. According to the way data is acquired, the algorithm is classified as a closed‐loop control with a non‐optimal type of control rule. Three examples are used to illustrate the methodology: (1) a conventional structure under typical dynamic loads; (2) an off‐shore platform under wave action; and (3) a structure with rubber isolators under earthquake motions.