Experimental performance evaluation of elastic friction damper

Earthquakes are natural disasters that can cause large-scale damage to humans and property. Many methods have been proposed to reduce the damage caused by earthquakes. These include dampers that are applied to structures to provide seismic reinforcement. Dampers absorb energy and reduce the response to earthquakes. However, in the case of an earthquake exceeding the allowable capacity, dampers may be damaged or permanently deformed, resulting in replacement of the dampers incurring considerable economic losses. In this study, to solve this problem, a new concept of an elastic friction damper that can reduce damage by applying a new material with recentering performance was developed; the performance of the damper was evaluated by experiments. The elastic friction damper is composed of polyurethane springs that provide recentering force by applying precompression, steel wires and permanent magnet cubes that provide energy dissipation capability. First, for the performance evaluation, a compression experiment was conducted to obtain the ideal precompression value of the polyurethane spring. In addition, a tensile experiment was performed to determine the elastic section and ductility of the steel wire. The frictional force generated by the attachment of permanent magnet cubes was determined in a previous research. Using these results, a detailed design of the elastic friction damper was developed, and six specimens were built for structural experiments. The design parameters of the specimens were set according to the precompression force applied on the polyurethane and the presence or absence of permanent magnets. The structural experiments were performed according to the loading protocol in which the displacement was increased as much as the elastic section of the steel wires. The results of the structural experiments showed that as the precompression value increased, the energy dissipation and the maximum load value increased. The friction behavior of the permanent magnet cubes continued until the end of the structural experiments. As a result of the experiment, SPM3 damper with 20% precompressed polyurethane spring and permanent magnet cube had the best maximum load and energy dissipation capacity, and SP3 damper without permanent magnet cube had the best recentering force. therefore, the damper incorporating the precompressed polyurethane springs and the permanent magnet cubes effectively reduced the residual strain and showed excellent performance in terms of the recentering force and the energy dissipation.