Characterization of small-size single-surface sliding bearing for seismic isolation

Friction pendulum bearings are widely recognized as crucial base isolation systems for enhancing structural reliability during seismic events. In this study, a small-size single surface sliding bearing was developed which consisted of a sliding plate and a housing plate fabricated from steel plates measuring 200 mm × 200 mm. The sliding plate had a concave surface with a radius of 559 mm, enabling a maximum horizontal displacement of 51 mm. The articulated slider was coated with a 4 mm thick layer of polytetrafluoroethylene (PTFE) type composite. Characterization of the bearing was done using a specially designed testing setup, which employed an actuator in the vertical direction to apply the vertical load to the bearing in a force-controlled manner and an actuator in the horizontal direction to apply the predefined displacement. The friction pendulum bearing was affixed between two steel plates. The upper plate was bolted to the vertical actuator head, and the lower plate was allowed to move in the horizontal direction with the help of roller assembly. The roller assembly ensured minimal shear force transmission from the friction pendulum bearing to the base. Reverse cyclic tests were conducted to determine the force-displacement behavior of the bearing. The tests involved subjecting the bearing to three complete cycles of sinusoidal loading at a slow forcing frequency. The axial load and lateral displacement were incrementally increased by multiples of 0.25 up to their respective capacity levels. These tests aimed to characterize the force-displacement behavior of bearing. The coefficient of friction was estimated to be in the range of 0.03-0.05.