Multi-stage friction pendulum systems (MSFPs), or more specifically the triple friction pendulum (TFP), are currently being developed as seismic isolation devices for buildings and other large structures. However, all current models are inadequate in properly modeling all facets of these devices. Either the model can only handle uni-directional ground motions while incorporating the kinetics of the TFP system, or the model ignores the kinetics and only models bi-directional motion. And in all cases, the model is linearized to simplify the equations.
This paper presents an all-in-one model that incorporates the full nonlinear kinetics of the TFP system while allowing for bi-directional ground motion. In this way, the model presented here is the most complete single model currently available. The model is developed in such a way that allows for easy expansion to any standard type of MSFP, simply by following the procedure outlined in this paper.
It was found that the nonlinear model can more accurately predict the experimental results for large displacements due to the nonlinear kinematics used to describe the system. It is also shown that the inertial effects of TFP system are negligible in normal operating regimes; however, in the event of uplift, the inertial effects may become significant. The model is also able to accurately predict the experimental results for complicated bi-directional ground motions.
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