Supplemental energy dissipation or damping systems are worldwide employed both in new and retrofit constructions in order to prevent structural damage, increase life-safety and achieve a desired level of performance A large number of devices have been developed in the past years, characterized by either hysteretic or viscous behavior. Despite substantial differences exist, all these devices are used with the philosophy of limiting or eliminating damage to the structural frame by dissipating much of the energy imparted by ground motion in elements not forming part of the gravity framing system. In this study a Lead Extrusion Damper (LED) has been experimentally and numerically investigated in the study. The device provides a resistive force by plastically extruding lead through an orifice created by an annular restriction between a tube and a bulged shaft. Cyclic tests according to EN 15129 were performed to obtain the basic characteristics of the LED for different displacement amplitudes. The damper exhibits a consistent rigid-plastic behavior without significant strength degradation; the shape of the hysteresis loops is essentially rectangular, resulting in an equivalent damping ratio of 0.55. The tested specimen was able to sustain multiple sequences of motion at the basic design earthquake displacement, demonstrating its ability to provide maintenance-free operation even in presence of repeated ground shakes. A 3D finite element model of the LED was formulated and used in a parametric study to investigate the distinct effects of the shaft diameter and the bulge diameter on the strength of the device. It is shown that the main parameter governing the response of the LED is s the annular area of the bulge that represents the projected face area of the bulge over which direct stress is applied to the shaft The results of the parametric study can be used to draw design charts to assist the manufacturers for the preliminary design of the system. Eventually, a novel Adaptive Lead Extrusion Damper (ALED) was assessed in preliminary tests. The ALED provides a “two-steps” rigid-plastic loop, with a substantial increase in the resisting force when a certain displacement is exceeded. Thereby the ALED could be used in structures to effectively modify their response depending on the magnitude of the ground motion.

Characterization and numerical assessment of lead extrusion damper with adaptive behavior

E. Bruschi;F. Macobatti;C. Pettorruso;V. Quaglini
2020-01-01

Abstract

Supplemental energy dissipation or damping systems are worldwide employed both in new and retrofit constructions in order to prevent structural damage, increase life-safety and achieve a desired level of performance A large number of devices have been developed in the past years, characterized by either hysteretic or viscous behavior. Despite substantial differences exist, all these devices are used with the philosophy of limiting or eliminating damage to the structural frame by dissipating much of the energy imparted by ground motion in elements not forming part of the gravity framing system. In this study a Lead Extrusion Damper (LED) has been experimentally and numerically investigated in the study. The device provides a resistive force by plastically extruding lead through an orifice created by an annular restriction between a tube and a bulged shaft. Cyclic tests according to EN 15129 were performed to obtain the basic characteristics of the LED for different displacement amplitudes. The damper exhibits a consistent rigid-plastic behavior without significant strength degradation; the shape of the hysteresis loops is essentially rectangular, resulting in an equivalent damping ratio of 0.55. The tested specimen was able to sustain multiple sequences of motion at the basic design earthquake displacement, demonstrating its ability to provide maintenance-free operation even in presence of repeated ground shakes. A 3D finite element model of the LED was formulated and used in a parametric study to investigate the distinct effects of the shaft diameter and the bulge diameter on the strength of the device. It is shown that the main parameter governing the response of the LED is s the annular area of the bulge that represents the projected face area of the bulge over which direct stress is applied to the shaft The results of the parametric study can be used to draw design charts to assist the manufacturers for the preliminary design of the system. Eventually, a novel Adaptive Lead Extrusion Damper (ALED) was assessed in preliminary tests. The ALED provides a “two-steps” rigid-plastic loop, with a substantial increase in the resisting force when a certain displacement is exceeded. Thereby the ALED could be used in structures to effectively modify their response depending on the magnitude of the ground motion.
2020
Proceedings of the 17th World Conference on Earthquake Engineering
Lead Extrusion Damper, rigid-plastic hysteretic loop, adaptive response, experiments, time history analyses
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1146568
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