Teflon Bearings in Base Isolation I: Testing

This paper describes the frictional properties of sheet type Teflon‐steel interfaces in relation to their application in sliding bearings for base‐isolated building and bridge structures. A series of laboratory experiments has been conducted on Teflon‐steel interfaces to determine the effect of sliding velocity, sliding acceleration, bearing pressure, type of Teflon, and surface finish on the frictional chracteristics of sliding bearings. It is found that sliding acceleration has insignificant effects on the recorded values of frictional force. However, sliding velocity and bearing pressure have important effects. Friction increases with increasing velocity up to a certain value of velocity beyond which it remains constant. Furthermore, friction drops with increasing pressure with a rate of reduction that is strongly dependent on velocity. It stabilizes at a value of pressure between 5,000 and 6,500 psi (34.5and44.9N/mm2). Substantial differences between breakaway (or static) coefficient of friction and sliding (or kinetic) coefficient of friction are observed. In general, the breakaway value is two‐four times larger than the sliding value.