Active seismic control strategy for comparable simultaneous reductions of more than one response

Abstract

Active control of structures is a widely investigated subject. In particular, control techniques using Linear Quadratic Regulator (LQR) and Pole Placement have been extensively used in structural control problems. However, while using these algorithms for controlling responses, most of the investigations focus on the maximum response reduction of a single response quantity like, the peak roof displacement or maximum inter story drift. Accordingly, the control parameters are adjusted, mostly using a trial approach. In this paper, simultaneous and sizeable reductions in more than one response quantity are achieved by adjusting the control parameters using the genetic algorithm. Two control algorithms are considered in the study, namely, the LQR and pole-placement techniques. The response quantities of interest are the peak roof displacement, maximum inter story drift and maximum base shear of a ten story regular shear building frame actively controlled with the help of active tendon system (ATS) placed at their optimal locations. For the study, four different types of earthquakes, two near fields and two far fields are considered. The comparable reductions in the responses are achieved by including a constraint in the genetic algorithm which does not allow the selection strategy to provide solutions for which response reduction is less than a specified value. Both response reduction and response reduction per unit control force are investigated to demonstrate the efficacy of the proposed method. The results of the study show that (i) it is possible to obtain comparable reductions of the three mentioned response quantities simultaneously by properly adjusting the control parameters; (ii) the control forces required to achieve the target response reductions are nearly the same as those required for the best control of a single response quantity using the trial approach; (iii) there exists optimal locations of the actuators/tendons for which best results (reductions per unit control force) are obtained, and (iv) the pole placement technique provides better reductions as compared to the LQR.