https://www.tiantiebuilding.com/products/friction-pendulum-seismic-isolation.html The friction pendulum isolators is composed of steel and friction materials like friction pendulum bearing . The natural vibration period of the upper structure is extended by the relative sliding of the spherical sliding surface. The appropriate radius of curvature of the sliding surface is selected according to the required natural vibration period. The damping coefficient is controlled by the friction coefficient; The sliding limit bolt is set to ensure the stability of the building in non-earthquake, and easy to cut in earthquake to ensure the deformation capacity. Features of Friction Pendulum Seismic Isolation Self-reset after earthquake. The vibration period has nothing to do with the carried mass.