Bridge bearings are devices for transferring loads and movements from the deck to the substructure and foundations. In highway bridge bearings movements are accommodated by the basic mechanisms of internal deformation (elastomeric), sliding (PTFE), or rolling. A large variety of bearings have evolved using various combinations of these mechanisms.
1. Elastomeric The elastomeric bearing allows the deck to translate and rotate, but also resists loads in the longitudinal, transverse and vertical directions. Loads are developed, and movement is accommodated by distorting the elastomeric pad.
2. Plane Sliding bearings usually consist of a low friction polymer, polytetrafluoroethylene (PTFE), sliding against a metal plate. This bearing does not accommodate rotational movement in the longitudinal or transverse directions and only resists loads in the vertical direction. Longitudinal or transverse loads can be accommodated by providing mechanical keys. The keys resist movement, and loads in a direction perpendicular to the keyway.
3. Roller Large longitudinal movements can be accommodated by these bearings, but vertical loads only can generally be resisted.