Friction pendulum bearing are used in the seismic isolation of buildings and bridges to reduce the effects of earthquakes. Typically, they consist of two sliders and a sliding plate, which are designed to slide relative to each other during an earthquake. The sliding surface between the plate and a slider is called the first sliding surface. By reducing the curvature of the first sliding surface, the vibration period of the structure can be extended, which reduces the acceleration of the structure during earthquakes. The sliding surface between the two sliders is called the second sliding surface, and it keeps the superstructure horizontal during earthquakes. The friction induced on the sliding surface provides energy dissipation and helps to reduce the impact of seismic forces on the building. The bearing behaves like a pendulum because of the re-centering mechanisms that keep the superstructure centered after an earthquake. One of the advantages of friction pendulum bearings is that they have an effective stiffness that is proportional to the weight of the supported structure. This means that they can easily overcome any inherent or accidental eccentricity problems, which can occur during earthquakes.