Pure rotation of column-top mounted elastomeric bearings

Typical installations of seismic isolation use rigid diaphragms to bound the end plates of the isolators. An alternative form of isolation involves placing the isolation plane on top of first floor columns, potentially resulting in flexible boundary conditions. To address this, an experimental program on a quarter-scale column-bearing subassembly was conducted to investigate how rotations of both top and bottom bearing end plates impact key design assumptions such as horizontal stiffness, rotational stiffness, and stability.