DESIGN, TESTING AND MODELING OF A NOVEL FRICTION DAMPER WITH ENHANCED RESISTANCE TO REPEATED SEISMIC LOADS

The study presents the design, experimental characterization and modeling of a novel friction damper with enhanced resistance to repeated seismic loads. This device provides energy dissipation by the friction force triggered between a moving shaft and a lead core prestressed within a rigid steel chamber. As there are not mechanical parts that are subjected to cyclic stresses, there is no risk of fatigue and the damper is expected to resist to a virtually unlimited number of load cycles. Two prototypes of the friction damper were tested according to the procedure established in 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 ?eff of more than 55%. Moreover, the damper is characterized by a low sensitivity to the loading rate and by the ability to withstand multiple cycles of motion at the design earthquake displacement without deterioration of performance, providing maintenance-free operation in presence of repeated ground shakes. A 3D finite element model of the friction damper is formulated in Abaqus and validated upon the results of the experimental tests. The model is then used in a parametric study to investigate the influence of the diameters of the shaft on the output force. The numerical data points are fitted by a simple model which can be used for designing the damper according to a specific quasi-static force.