Hybrid system of base-isolated structures with tuned tandem mass damper-inerters considering internal friction

A hybrid system combining base-isolated structures (BIS) with tuned tandem mass damperinerters (TTMDI), named BIS-TTMDI, is presented. This system can reduce base isolation floor (BIF) deformation while achieving superior seismic performance. However, current investigations of TTMDI are limited to the linear assumption of inerters. In practical terms, the inerter demonstrates nonlinear behavior, characterized by internal friction. Neglecting internal friction can potentially causes design errors and unsatisfactory control performance of TTMDI. In order to address this issue, a combined nonlinearity model that considers Coulomb friction and viscous friction is proposed to characterize the internal friction of the inerter. The nonlinear parameters are identified and validated through mechanical performance tests. This proposed nonlinearity model of the inerter is then incorporated into the hybrid system of BIS with TTMDI, referred to as BIS-NTTMDI. Employing the proposed nonlinearity model of the inerter, an optimization design method for NTTMDI is developed to obtain the optimal tuning parameters. The robustness and stroke of NTTMDI are scrutinized and compared with those of TTMDI. Furthermore, a nonlinear response history analysis is conducted to systematically assess the control performance of BISNTTMDI. The results underscore the importance of considering the internal friction of the inerter in designing BIS-NTTMDI to achieve reliable control performance. Employing the proposed nonlinearity model of the inerter, the influence of internal friction can be appropriately compensated for. Compared with BIS, the optimized BIS-NTTMDI has achieved a maximum reduction of 21.5 % in the displacement of the BIF in this study.