Teflon Bearings in Base Isolation II: Modeling

A mathematical model of the factional behavior of Teflon sliding bearings for conditions of interest in base isolation is developed. The calibration of the model is based on extensive experimental data that were presented in an accompanying paper. The model is capable of accounting for: (1) Unidirectional and multidirectional motion at the Teflon‐steel interface; (2) velocity and pressure dependence of the coefficient of sliding friction; and (3) breakaway (or static) friction effects. The model is characterized by four parameters. These are the minimum and maximum values of the sliding coefficient of friction, the ratio of breakaway to sliding coefficient of friction at initiation of sliding and a parameter that describes the variation of the sliding coefficient of friction with velocity. Values of these parameters are presented for sixteen combinations of type of Teflon, bearing pressure and condition (surface roughness) of mating steel surface. Applications of the model in the analysis/design of a sliding isolation system are presented and the effects of bearing pressure and breakaway friction are evaluated. Furthermore, an assessment of the implications of using Coulomb's constant friction model rather than the developed model is presented.