Seismic Control and Performance Assessment of Isolated Bridges Using Integration of Negative Stiffness and Inerter-Based Supplemental Control Devices

The present study introduces inerter-based absorbers (IVAs), negative stiffness dampers (NSDs), and their synergistic combination as supplemental control strategies for a multispan continuous deck isolated bridge structure. An inerter functions as a device capable of generating force proportional to relative acceleration between its terminals. Conversely, a passive negative stiffness mechanism is designed to generate force that aids in motion. Specifically, tuned inerter dampers (TIDs), negative stiffness amplifying dampers (NSADs or simply NSDs), and their synergistic combination in the form of negative stiffness inerter dampers (NSIDs) are introduced at bearing levels as supplemental dissipation mechanisms or control devices. The continuous-span bridge is simplified and modelled as a reduced lumped mass system by appropriate static condensation of the degrees of freedom. The isolated bridge with supplemental control devices is subjected to typical stationary ground motion with specified power spectral density. Stochastic responses such as mean square shear at the bearing level and pier base, deck acceleration, and bearing displacement are evaluated. The stochastic assessment of three negative stiffness and inerter mechanisms, viz., NSD, TID, and NSID, shows that biobjective optimization is necessary for the best control performance. An optimization framework is also introduced, minimizing the stochastic responses and obtaining the corresponding optimal parameters. A set of real earthquake records containing near fault (NF) and far field (FF) types of excitations are used for the performance assessment of optimized control devices. Among the three dissipation mechanisms, optimal NSID performs better, and the required optimum parameters are lower in magnitude, forming an important design criterion.