FRICTION IN BRIDGE BEARINGS WITH CONTAMINATED TFE SLIDE SURFACE

Tetrafluoroethylene (TFE) is commonly used as a slide surface mating with polished stainless steel in bridge bearings that accommodate translation and rotation of the superstructure relative to the substructure. The primary requirement of die slide surface is a low coefficient of friction that is maintained throughout the service life of the bearing. The paper reports on a laboratory investigation comprising 14 tests undertaken at room temperature under simulated field conditions that was performed to determine the effect of contamination on the coefficient of friction in a lubricated TFE/stainless steel interface. It is shown that the friction of a lubricated surface increases significantly with a relatively low amount of contamination in the form of unhydrated portland cement in the interface, emphasizing the need for assembling bearings in a dust-free environment and avoiding disassembling of bearings on site. The influences of the degree of contamination on die coefficient of friction at initial movement and after 200 cycles of movement, as well as on the peak value of the coefficient of friction recorded during a test, are discussed.