Rotation of High Load Multirotational Bridge Bearings

High load multirotational (HLMR) bridge bearings are used to support large loads while accommodating rotations resulting from traffic loading, construction tolerances, thermal effects, and other deformations. Pot, disk, and spherical bearings qualify as HLMR bearings; a series of experiments were performed to evaluate their behavior, and to develop design recommendations. The experiments were performed on a specially designed rig that applies a constant compressive load, a constant shear force, and a cyclic rotation. Sixteen tests were performed on pot bearings, four on spherical bearings, and two on disk bearings. The test results are summarized, and general observations on the bearing behavior and design considerations are noted in this paper. Each bearing type has advantages and potential problems. Pot bearings are able to support large compressive loads, but their elastomer might leak and their sealing rings might suffer wear or damage. Disk bearings are susceptible to uplift during rotation, which may limit their use in bearings with polytetrafluoroethylene (PTFE) sliding surfaces. Spherical bearings are able to sustain large rotations but require proper clearances, very smooth and accurate machining.