This study introduces a new energy dissipation device with a high damping capacity for the seismic protection of buildings. The device exploits the friction losses between a movable shaft and a lead core to dissipate the seismic energy and takes advantage of the prestressing of the lead material to control the friction force. Numerical analyses are introduced to evaluate the influence of prestressing on the axial force of the device. Cyclic tests performed on a prototype demonstrate the high damping capability, with an equivalent damping ratio ξeff of approximately 55%, a robust and stable response over repeated cycles and a low sensitivity of the mechanical properties to the frequency, suggesting that the proposed device may be a potentially effective solution for providing supplementary energy dissipation to structures in seismic areas. Moreover, the device is able to endure multiple cycles of motion at the basic design earthquake displacement, ensuring maintenance-free operation even in presence of repeated ground shakes.

Supplemental energy dissipation devices are employed both in new and retrofitted constructions in order to prevent structural damage, increase life-safety and achieve a desired level of performance. Among these devices, hysteretic dampers have been proven to be an appropriate and economically affordable solution to reduce the vulnerability of ordinary structures, such as residential, school and industrial buildings. The study presents an experimental and numerical investigation of a Prestressed Lead Extrusion Damper (P-LED), an emerging energy dissipation device which provides energy dissipation by means of the plastic extrusion of lead through an orifice created between a containing tube and a moving shaft and achieves high specific output force by preloading of the working material. The experimental investigation is performed following the provisions set in the European standard EN 15129 for Displacement Dependent Devices. A damper prototype is tested in cyclic tests at different displacement amplitudes and in a monotonic ramp up to the amplified design deformation. The damper shows a rigid-plastic behavior, without strength degradation regardless of the imposed deflection; the shape of the hysteresis loops is essentially rectangular, resulting in an effective damping of 0.55, very close to the maximum theoretical level; the device is able to sustain multiple cycles of motion at the basic design earthquake displacement, anticipating a maintenance-free operation even in presence of repeated ground shakes. A 3D finite element model of the P-LED is formulated in Abaqus and validated upon the results of the experimental tests. The model enlightens that the output force of the damper accounts for two contributions, namely the extrusion force of the lead and the friction force between the lead and the moving shaft. The model is then used in a parametric study to investigate the influence of the device dimensions, namely the diameters of the shaft, of the containing tube and of the bulge, and the length of the shaft, on the output force. The numerical data points are fitted by a simple model which can be used for design of the damper to a specific quasi-static force.

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Past earthquakes have highlighted the seismic vulnerability of prefabricated industrial sheds typical of past Italian building practices. Such buildings typically exhibited rigid collapse mechanisms due to the absence of rigid links between columns, beams, and roof elements. This study aims at presenting the experimental and numerical assessment of a novel dissipative connection system (DCS) designed to improve the seismic performance of prefabricated sheds. The device, which is placed on the top of columns, exploits the movement of a rigid slider on a sloped surface to dissipate seismic energy and control the lateral displacement of the beam, and to provide a recentering effect at the end of the earthquake. The backbone curve of the DCS, and the effect of vertical load, sliding velocity, and number of cycles were assessed in experimental tests conducted on a scaled prototype, according to a test protocol designed accounting for similarity requirements. In the second part of the study, non-linear dynamic analyses were performed on a finite element model of a portal frame implementing, at beam-column joints, either the DCS or a pure friction connection. The results highlighted the effectiveness of the DCS in controlling beam-to-column displacements, reducing shear forces on the top of columns, and limiting residual displacements that can accrue during ground motion sequences.