Shaking table test to investigate the size effect on the seismic response of a low-cost friction pendulum system

To enhance the seismic resilience of reinforced concrete (RC) bridge piers, a novel friction pendulum system was developed. It consisted of a friction pendulum and a spherical sliding surface that were constructed from conventional steel and concrete. In comparison to commercial isolators, the complex spherical shape was realised using a three-dimensional printer to fabricate an acrylic glass mold, which allowed a significant cost savings in production. The system was distinguished by stable oscillation and a significant reduction in response accelerations on the flat surface. The inclined part acted as a restoring force that limited the residual displacement. However, these properties were confirmed experimentally using only small specimens. To characterise the fundamental properties of the system, a bidirectional shaking table test was performed in this study to investigate the size effect on the seismic performance of the proposed system. The test results demonstrate that the excellent performance in reducing the response acceleration and residual displacement is independent of the specimen size. In addition to the dependency of the friction coefficient on the sliding velocity and axial pressure, the impact force was observed to increase with the superstructure weight. Furthermore, a simplified method for estimating the maximum and residual displacements of the proposed system is presented.