Optimal control of high-rise building structures against earthquake excitations using independent stories as TMD

Abstract

In this paper, in order to control the behavior of tall building structures against vibrations caused by earthquakes, the parameters of a new passive control system named “independent story” are optimized. This control system is installed like a large tuned mass damper in the main story of the building. Moreover, in order to improve the performance of this control system, six liquid viscous dampers connected from the roof of an independent story to the main story of the building, have also been used to increase damping of the system. The main goal of the present research is to optimize the parameters of this system, including selecting the optimal story/stories of the building to install the independent story/stories, such that the maximum reduction in the mean values of the maximum displacement and maximum acceleration responses of different stories of the building can be obtained, simultaneously. To evaluate the performance of the proposed control system, as a numerical example, a 3-D model of a twelve-story steel building structure is selected for which three degrees of freedom in each story have been considered. Then, a deep search is conducted to find the story/stories of the building at which the independent story control system along with the related supplemental liquid viscous dampers can be constructed/installed such that the best performance of this control system in response reduction of the building can be obtained. Finally, the optimal values of the mass and damping of the supplemental dampers of this system are found to be about 6% of the total mass of the building, and 13 kN-sec/mm, respectively; and the eighth and twelfth stories of the building are the best places for implementation of the proposed control system. By applying the optimal values of all the design parameters of the IS control system, the mean values of the building roof story response reductions were obtained to be about: 28.60% and 26.67% reduction on maximum displacement responses in x and y directions, respectively; and those of the maximum acceleration responses as 43% and 48.89%.