The Earthquake Engineering Online Archive

Earthquake simulator testing of a combined sliding bearing and rubber bearing isolation system

Kelly, James M.; Chalhoub, Michel S.

UCB/EERC-87/04, Earthquake Engineering Research Center, University of California, Berkeley, 1987, 172 pages (525/K44/1990E)

Essential requirements of a base isolation system include wind restraint, stability, and fail-safe capacity. A new base isolation system combining sliders and rubber bearings inherently satisfies all three requirements and possesses other advantages. This type of system was tested on the earthquake simulator at the Univ. of California at Berkeley by installing it under the base of a one-fourth-scale nine-story steel structure and subjecting it to different earthquake inputs. The base behaves as fixed for low-magnitude inputs. When sliding starts, the rubber bearings provide additional stiffness and recentering. Under very severe inputs, the tension devices reach their locking limit and cause a large increase in the stiffness of the system. Areas of base shear hysteresis loops are drastically enlarged by the addition of sliders. Displacements are better controlled than the ones for a purely elastomeric isolation system. Vertical deflections due to large horizontal drift encountered in solely rubber systems are eliminated. The fail-safe capacity is provided by the tension restrainers and by the constant contact of the sliders with the base. The sliders were also tested separately on a static rig. The friction coefficient for Teflon-stainless steel increases with sliding velocity and decreases with pressure.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-87-04.pdf (15 MB)