Seismic multi-objective stochastic parameters optimization of multiple tuned mass damper system for a large podium twin towers structure

The lateral-torsional coupled dynamic response under earthquake excitation is a critical problem for eccentric building structures. To control the hazardous coupled seismic response, a tuned mass damper (TMD) is an attractive vibration control device. A multiple TMD (MTMD) system, which is composed by several TMDs with different frequencies and damping ratios, has a better structural control effect under stochastic excitation with a wide frequency range such as earthquake. To improve the lateral-torsional coupled seismic mitigation performance of MTMD for eccentric structures, a multi-objective stochastic parameters optimization method is proposed, and a building with a large podium and twin towers is proposed as the case study. Considering the randomness of earthquakes, a stationary white noise stochastic process based on the Kanai-Tajimi spectrum is used as the input in the optimization. According to structural modal shapes, three TMDs are distributed in the podium, left tower and right tower respectively in the X direction, and two TMDs are in the left tower and right tower respectively in the Y direction, while both the maximum and root mean square (RMS) displacements of top stories of the podium, left tower and right tower are all considered in the optimization. Artificial fish swarm algorithm (AFSA) is used to search optimized parameters of MTMD in this study. For comparison, a MTMD system designed based on the traditional method is presented. Numerical results show that under bi-directional earthquake excitations, the proposed MTMD system has the best seismic mitigation effect generally, in both displacement and acceleration responses. Though the proposed MTMD system is aimed at X- and Y- directional translational responses, it can control torsional responses effectively as well.