Optimized Negative Stiffness Friction Isolator–Tuned Viscous Mass Damper System for Base-Isolated Buildings

A negative stiffness friction isolator-tuned viscous mass damper system (NSFI-TVMD) is proposed and optimized to boost the aseismic performance of base-isolated buildings (BIBs). It features horizontally enhanced energy dissipation but concurrently inherits vertical load-carrying capabilities from loaded friction isolators. For the best mitigation performance with the restriction of load-carrying, this proposed NSFI-TVMD is optimized via two steps. First, its linear simplification (i.e., by linearizing the nonlinear friction force) is optimized by utilizing the pseudo-fixed-point method, yielding a series of approximate analytical solutions. On top of the linear solutions, the nonlinear effects are then accounted for by deriving a series of nonlinear modification factors. The combination of the results of these two steps leads to the semianalytical optimization solution of the parameters of the NSFI-TVMD. To ensure the proposed additional damping system is beneficial, a formula is also proposed to identify the range of its parameters. Numerical examples by the nonlinear time-history analysis (NTHA) of a typical 8-storey BIB under an ensemble of both far-field (FF) and near-fault (NF) earthquake ground motions demonstrate the capability and performance of the optimized NSFI-TVMD over existing techniques.