EFFECTIVE COEFFICIENT OF FRICTION OF STEEL BRIDGE BEARINGS

A study to determine experimentally the effective coefficient of friction of four classes of steel bridge bearings used by the Oklahoma Department of Transportation is reported. As-built, rusted, and in situ (debris at the moving surfaces) conditions were tested by using full-scale bearings under normal loads to 250,000 lb. In addition, the effects of manufacturing tolerances on bearing performance were analyzed. From the tests it was found that unturned pipe rollers exhibit the lowest effective coefficient of friction of the four rolling devices tested. For turned pipe rollers it was found that the equivalent coefficient of friction is a function of the amount of horizontal movement from the centerline. A geometric explanation was devised, and excellent agreement between predicted and measured results was achieved. Tests with a pintle rocker showed that fabrication inaccuracies, especially in the sole plate socket radius, can significantly affect the performance and effective coefficient of friction of the bearing. In all cases, tests with rusted bearing plates or with sand spread over the lower bearing plate showed significant increases in the effective coefficient of friction. (Author)