Friction in Bridge Bearings with Contaminated TFE Slide Surface .pdfVIP

F R I C T I O N IN B R I D G E B E A R I N G S WITH C O N T A M I N A T E D T F E SLIDE S U R F A C E By T. I. Campbell, t Member, ASCE, M. J. Fatemi,2 and D. G. Manning3 ABSTRACT: Tetrafluoroethylene(TFE) is commonlyused as a slidesurfacemating with polished stainlesssteel in bridge bearings that accommodatetranslation and . rotationof the superstructurerelativeto the substructure.The primaryrequirement d e of the slide surface is a low coefficientof friction that is maintained throughout v r the service life of the bearing. The paper reports on a laboratory investigation e s e comprising 14 tests undertaken at room temperature under simulated field con- r s ditionsthat was performed to determine the effect of contaminationon the coef- t h ficientof frictionin a lubricatedTFE/stainlesssteel interface. It is shownthat the g i r frictionof a lubricatedsurfaceincreasessignificantlywith a relativelylow amount l l of contaminationin the form of unhydrated portland cement in the interface, a ; emphasizingthe need for assemblingbearingsin a dust-freeenvironmentand avoid- y l n ing disassemblingof bearingson site. The influencesof the degreeof contamination o e on the coefficientof frictionat initialmovementand after 200 cyclesof movement, s u as well as on the peak value of the coefficientof frictionrecorded during a test, l a are discussed. n o s r e INTRODUCTION p r o F E. Tetrafluoroethylene (TFE) is commonly used to provide the slide surface C in a bridge bearing due to its low friction properties, as well as