HIGH-STRAIN TESTS ON LEAD-RUBBER BEARINGS FOR EARTHQUAKE LOADINGS.

The use of laminated rubber bearings, with damping provided by lead plugs, is now an accepted technology throughout the world for the base isolation of buildings and bridge decks. Dynamic tests on two lead-rubber bearings, 280 multiplied by 230 multiplied by 113 mm, are described in which a dynamic actuator was used to apply shear displacements of plus or minus 10 to plus or minus 140 mm at frequencies of 0. 1 to 3 Hz, giving shear strains in the rubber of up to plus or minus 200%. The weight of the structure on the bearing was applied by a vertical jacking system and ranged from 35 to 455 kN. Sequences of cycles were performed to simulate earthquake conditions and force-displacement hysteresis loops were obtained.