H. Toopchi-Nezhad¹, M.J. Tait², and R.G. Drysdale³

1. Post Doctoral Fellow, Department of Civil Engineering, McMaster University, Hamilton, ON, L8S 4L7, Canada, toopchh@mcmaster.ca
2. Assistant Professor, Department of Civil Engineering, McMaster University, taitm@mcmaster.ca
3. Professor Emeritus, Department of Civil Engineering, McMaster University, drysdale@mcmaster.ca

ABSTRACT

Stable unbonded-fiber reinforced elastomeric isolator (SU-FREI) bearings have been designed for earthquake protection of relatively rigid masonry low rise buildings. They exhibit rollover deformation under lateral loads due to both the unbonded boundary conditions of the bearings at their top and bottom faces, and lack of bending rigidity of the fiber reinforcement sheets. At extreme lateral displacement when the originally vertical faces (end faces) of a rectangular SUFREI bearing come in contact with top and bottom horizontal contact supports, the bearing exhibits increased lateral stiffness resulting in a stable condition. Modifications to the geometry of the end faces are expected to significantly alter the lateral response behaviour of a SU-FREI bearing. A preliminary study conducted to investigate the influence of bearing end geometry on the response behavior of a base isolated masonry building is reported in this paper. The preliminary results suggest that the bearing end geometry can be considered as a new design variable for SU-FREI bearings.

KEYWORDS: masonry building, base isolation, seismic mitigation, fiber reinforced elastomeric isolator, stable unbonded bearing, end geometry, frequency, stiffness.

A7-4