Optimal design of inerter-assisted series tuned mass dampers for seismic vibration control of multi-story buildings

This work introduces a framework for the optimal design of inerter-assisted series tuned mass dampers (STMDI) placed at the top story of a multi-story building under ground motion and performs comparative research to assess its effectiveness against conventional TMDI. The identical inertance ratio and total mass ratio are taken into consideration for the optimization of both control systems. In the frequency-domain analysis, the five design variables of the STMDI are optimized based on the minimization of the peak amplitude of the displacement transfer function at the top story of the building using the genetic algorithm (GA). The optimized variables are damping ratios (ξ1and ξ2), tuning frequency ratios (f1and f2), and mass ratio of the first to second TMD mass (µh). The proposed control system is applied to a 4-story, an 8-story, and a 16-story case-studies, and the optimal parameters are verified using eighty-five historical benchmark earthquakes in time domain analysis. These records are divided into three different groups according to their frequency content, i.e. PGA/PGV ratio: high, intermediate, and low. The results demonstrate that the STMDI performs better than the TMDI at the same mass and inertance ratio, especially at excitation frequencies close to resonance. The most important advantage of STMDI compared to TMDI is that it provides this performance in a wider frequency range and in an almost similar way. Finally, the seismic performances of STMDI and TMDI are compared considering ground motions with different frequency content.