Characterization of the Frictional Behavior of Steel-Polymer Interfaces with Pronounced Stick-Slip Effect for Use in Seismic Isolation

The frictional behavior of steel-PTFE interfaces for use in seismic isolation has been studied extensively in the past. However, alternative polymers, such as polyethylenes and polyamides, have also been implemented in seismic isolation applications in order to also achieve good frictional properties and reduce wear and costs, although the publicly available information on their frictional behavior for structural applications is much more limited. Some of these alternative polymers may exhibit a more pronounced stick-slip effect, about which only limited results exist despite the consensus that it may strongly influence the response of the isolated superstructure. Furthermore, the necessary testing conditions to obtain relevant and reliable data about the frictional behavior of these steel-polymer interfaces are not well established. We present the results of an experimental program aimed at characterizing the frictional behavior of three polyethylenes sliding on hot-dipped galvanized steel under conditions similar to those applicable to seismic isolators: sliding velocities up to 200 mm/s, normal pressures up to 39 MPa, and polymer specimen diameters up to 101.6 mm. We investigate how several testing variables, such as sliding history, specimen size, normal pressure, wear, and load dwell, affect the frictional behavior of these polymers. Our findings provide the basis for improved modeling of the frictional behavior of steel-polyethylene interfaces as well as improved design of testing procedures to characterize the frictional behavior of other steel-polymer interfaces-especially those with a pronounced stick-slip effect-for their use in seismic isolation.