Displacement control and uplift restraint for base-isolated structures

Abstract

A displacement‐control and uplift‐restraint device that can be installed within multilayer, elastomeric base‐isolation bearings is described. The device acts to limit the displacement of the bearings and is also able to resist tension forces associated with uplift. The device was tested in earthquake simulator tests of a nine‐story, one‐quarter scale steel structure conducted at the Earthquake Simulator Laboratory of the Earthquake Engineering Research Center of the University of California, Berkeley. The test structure was isolated using eight multilayer, elastomeric bearings, four of which were located at the corners of the structure and contained the restraint devices. The system was subjected to a large number of simulated earthquakes. In some tests the devices acted to control the displacements, and in others, where uplift forces were generated, the devices simultaneously limited the displacements and carried the uplift forces. The test results show that the action of the devices is smooth and that there is no sudden jerk when one comes into action. The devices can perform as a fail‐safe system for base‐isolated buildings. In this role they would be designed to act only when the ground motion is greater than that for which the base‐isolation system has been designed.