Prestressed Lead Damper for seismic protection of structure

The study presents the design and experimental characterization of a lead friction damper with improved resistance to repeated seismic loads. The damper provides energy dissipation by the friction force triggered between a moving shaft and a lead core prestressed within a steel chamber. Thanks to the ability of lead to restore its properties by strain relief due to static recrystallization immediately after deformation, the damper is not affected by low-cycle fatigue. Prototypes of the damper were subjected to the test procedure recommended by the European standard EN 15129 for Displacement Dependent Devices, fulfilling the relevant requirements. The damper provides a stable response over repeated cycles, characterized by an essentially rectangular hysteresis loop with an equivalent viscous damping ratio ξeff > 55%, a low sensitivity on the loading rate, and the ability to withstand multiple cycles of deformation without deterioration of performance, ensuring maintenance-free operation in presence of repeated ground shakes.