Seismic component devices

Struct. Control Health Monit.

2017

Summary The focus of this paper is on analytical modeling of a novel type of passive friction damper for seismic hazard mitigation of structures. The proposed seismic damping device, which is termed as passive electromagnetic eddy current friction damper, utilizes a solid‐friction mechanism in parallel with an eddy current damping mechanism to maximize the dissipation of input seismic energy through a smooth sliding in the damper. In this passive damper, friction force is produced through magnetic repulsive action between two permanent magnetic sources magnetized in the direction normal to the friction surface, and the eddy current damping force is generated because of the motion of the permanent magnetic sources in the vicinity of a conductor. The friction and eddy current damping parts are able to individually produce ideal rectangular and elliptical hysteresis loops, respectively; which, when combined in the proposed device, are able to accomplish a higher input seismic energy dissipation than that only by the friction mechanism. This damper is implemented on a two‐degree‐of‐freedom system to demonstrate its capability in reducing seismic responses of frame building structures. The numerical results show that the seismic performance of the proposed damper is comparable with that of passive magnetorheological damper of the same force capacity. However, the cost of the device is likely to be quite lesser than that of a magnetorheological damper.

Section: Introductionmentioning

confidence: 99%

A passive electromagnetic eddy current friction damper (PEMECFD): Theoretical and analytical modeling

Struct. Control Health Monit.

2017

“…Energy dissipation has a significant role in vibration control of structural and mechanical systems subjected to excessive external excitations. The capability of a dynamical system to dissipate vibration-induced kinetic energy can be significantly improved by the use of supplemental dampers (Agrawal and Amjadian, 2016; Ebrahimi et al, 2011; He and Agrawal, 2007; Karnopp, 1989; Soong and Spencer, 2002; Xu et al, 2007). This improved energy dissipation capability limits damage in the dynamical system as the mechanism of energy dissipation is localized in the damper instead of in critical components of the dynamical system in the form of hysteretic deformation (Christopoulos and Filatrault, 2006).…”

Section: Introductionmentioning

confidence: 99%

Planar arrangement of permanent magnets in design of a magneto-solid damper by finite element method

Journal of Intelligent Material Systems and Structures

2020

This article studies the energy dissipation mechanism of a proposed magneto-solid damper using a three-dimensional finite element model developed in COMSOL Multiphysics software. The energy dissipation mechanism of the magneto-solid damper dissipates energy through combined actions of friction and eddy current damping. The key components of the magneto-solid damper are a steel plate, two copper plates placed on two sides of the steel plate in parallel, and two planar arrays of permanent magnets each one placed between the steel plate and one of the copper plates. These arrays are kept away from the steel and copper plates through narrow gaps; the gaps between them and the steel plate are filled with thin friction pads made of non-magnetic materials. The attractive magnetic interaction between the permanent magnet arrays and the steel plate provides the normal force for the friction developed between the friction pads and the steel plate when the permanent magnet arrays move relative to the steel plate. The motion of the permanent magnet arrays relative to the copper plates, on the other hand, provides the eddy current damping. The main contribution of this article is to optimize the pole arrangement of the permanent magnets and demonstrate that how the optimum pole arrangement can affect the energy dissipation capacity of the magneto-solid damper. The analysis results show that, for a given number and size of the permanent magnets, alternate arrangement of the poles of permanent magnets along the direction of their motion is the most optimal case resulting in large and smooth hysteresis force–displacement loops. This pole arrangement has also been used to find the optimum size of the steel and copper plates by addressing edge and skin effects in the design of the damper.

“…A wide variety of semiactive control devices have been proposed and developed for the seismic protection of bridges during the last few decades . The most notable examples are variable stiffness device, variable friction damper, variable viscous fluid damper, and controllable fluid dampers such as magnetorheological dampers .…”

Section: Introductionmentioning

confidence: 99%

“…The most efficient strategy for enhancing the seismic performance of a bridge is to modify its dynamic characteristics, such as natural frequency and damping, by installing seismic protective devices between its deck and piers or two abutments. 1 These devices are capable of absorbing or dissipating a substantial portion of the input seismic energy, thereby reducing the seismic demands of the deck and piers significantly. These devices are typically classified into three broad categories according to their energy absorption and dissipation mechanisms: passive, active, and semiactive control systems.…”

Section: Introductionmentioning

confidence: 99%

“…2,3 A wide variety of semiactive control devices have been proposed and developed for the seismic protection of bridges during the last few decades. 1,4 The most notable examples are variable stiffness device, 5 variable friction damper, 6 variable viscous fluid damper, 7 and controllable fluid dampers such as magnetorheological dampers. 8 The variable friction damper is one of the most popular among these devices because of its simple and reliable energy dissipation mechanism, low costs of installation, operation, and maintenance.…”

Section: Introductionmentioning

confidence: 99%

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Feasibility study of using a semiactive electromagnetic friction damper for seismic response control of horizontally curved bridges

Struct Control Health Monit

2019

Summary Semiactive control systems have been found to be more effective than passive and active control systems for seismic protection of bridges because of their reliable and adaptable characteristics. This paper presents a comprehensive investigation on the modeling and design of a semiactive electromagnetic friction damper (SEMFD) for the seismic response control of horizontally curved bridges. The proposed SEMFD possesses a simple configuration consisting of a ferromagnetic plate and two arrays of ferromagnetic core coils (FCs) attached to the two sides of the ferromagnetic plate through two friction pads. The attractive magnetic interaction between the FCs arrays and the ferromagnetic plate creates the normal force, which generates friction force as the friction pads and the ferromagnetic plate move relative to each other. The magnitude of this force can be controlled by varying the control current passing through the FCs. This semiactive controller, designed based on the optimal linear quadratic Gaussian control method, is capable of reducing the undesirable effects of stick–slip motion in the damper, while restoring the piston of the SEMFD to its initial position at the end of the excitation. The capability of the proposed SEMFD to mitigate the rigid‐body motion of decks of horizontally curved bridges is demonstrated by implementing it into the dynamic model of a horizontally curved bridge prototype. The numerical results indicate that the proposed SEMFD is effective in limiting the motion of the deck and thereby preventing it from unseating, which is one of the most common modes of failure among horizontally curved bridges.