Nonlinear modeling for dynamic analysis of base-isolated structures

A nonlinear hysteretic model for high-damping isolation bearings and a simple procedure for the identification of mechanical parameters starting from the isolation properties verified by tests are proposed. The nonlinear modeling of the lateral-force-resisting system is carried out including the variation of mechanical characteristics with the axial load for the columns and with the sign of the bending moment for the beams. The effects of material nonlinearities of isolation and lateral-force-resisting systems are taken on the right hand side of the equations of motion, and considered as pseudo-forces applied to the equivalent linear system. The dynamic response is finally obtained with a complex-mode superposition and an iteration procedure searching for the nonlinear contributions satisfying both the equations of motion and the constitutive laws.