Performance of Lead-Rubber and Sliding Bearings

[garcia]

Performance of Lead-Rubber and Sliding Bearings under Different Axial Load and Velocity Conditions

By: Gianmario Benzoni, Chiara Casarotti
Report No. SRMD–2006/05-rev3
May 2008

Department of Structural Engineering
University of California, San Diego
La Jolla, California 92093-0085


ABSTRACT:
A series of tests on full scale devices for bridge application were completed. Two types of isolators were considered: lead-rubber bearings and sliding bearings. The main performance characteristics of these devices were already acquired through extensive testing campaigns designed for their specific applications. A more systematic analysis of their performance was considered necessary to enrich the knowledge of the device behavior under different loading conditions. Specifically the focus of this project was to address the effects of the applied axial load, the varying levels of velocity and the repetition of cycles on the performance characteristics. The response variations were analyzed, for a low, medium and high level of applied vertical load, defined based on the design load of the bearing. A large spectrum of testing velocities was applied, ranging from very slow tests (0.254 mm/s) to high speed tests (1270 mm/s). Peak shear force, yield force, stiffness, energy dissipated per cycle, friction coefficient and damping was estimated and compared among the different loading conditions. A specific numerical model, for lead-rubber bearings, able to take into account the effects of strain rate and repetition of cycles, is proposed. The effects of bi-directional motions and of unequal distribution of vertical loads between bearings installed in parallel were also investigated.

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[Grunf]

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