A recently developed semi-active control system employing magnetorheological (MR) fluid dampers is presented for vibration control of wind excited tall buildings. Numerical simulation studies are performed to demonstrate the efficacy of the semi-actively controlled MR fluid dampers on the third ASCE benchmark problem. Multiple MR fluid dampers are assumed to be installed in the 76-story building. Genetic algorithm is applied to determine the optimal locations and capacities of the MR fluid dampers. Clipped optimal controller is designed to control the MR fluid dampers based on the acceleration feedback. Due to the intrinsic nonlinear behavior of the MR fluid dampers, the performance of the control system varies with the magnitude of the external wind forces. Thus, several cases with different wind speeds are considered in the numerical simulation.
The semi-actively controlled MR fluid dampers were shown to effectively reduce both the peak and RMS responses under various wind force conditions. The performance of the semi-active control system was found to be significantly better than the performance of the passive control system, and it was quite comparable to the performance of the control system with an active tuned mass damper (ATMD). The ratios for the peak and RMS displacement reduction of the 76-story building response with the semi-active control system were found to be superior to those with an active tuned mass damper. However, the peak acceleration was increased by 17% over that with the active tuned mass damper.
