Eddy Current Tuned Mass Damper Research Articles

Eddy-Current Tuned Mass Dampers for Mitigation of Wind-Induced Response of the Noor III Solar Tower: Design, Installation, and Validation

AbstractThe Noor III solar tower of the Ouarzazate Solar Power Station in Morocco is a very slender structure sensitive to wind excitations. Hence, tuned mass dampers (TMDs) were employed to reduce...

Vibration control of stress ribbon bridges subjected to moving vehicles

Stress ribbon bridges experience excessive vibration when subjected to moving vehicles due to flexibility and low damping, affecting the running safety and ride comfort of the vehicles. It is of great challenge to suppress the vibration of a vehicle-stress ribbon bridge (VSRB) system because of the strong geometric nonlinearity of the stress ribbon bridge, which might also lead to the inapplicability of the conventional optimal design of tuned mass dampers (TMD). This paper proposes an eddy-current tuned mass damper (ECTMD) and its parameter optimization method for suppressing the excessive vibration of stress ribbon bridges subjected to moving vehicles. A dynamic analysis method of the VSRB system is first presented for evaluating the control performance of the ECTMD. Then, a response surface method is proposed to optimize the parameters of the ECTMD for improving control performance. The control performance of the ECTMD optimized by the proposed procedure is validated using a numerical study of a real stress ribbon bridge. Numerical results demonstrate that the conventional design methodology of the TMD based on the linear theory is not the optimal design for the VSRB system due to its nonlinear vibration feature, whereas the proposed response surface method well optimizes the ECTMD's parameters, thus achieving the optimal control performance. This study provides an effective passive control approach for reducing the dynamic responses of stress ribbon bridges excited by moving vehicles.

A hybrid vibration mitigation method based on the crowd flow control and tuned mass damper on a footbridge

This study proposes a hybrid mitigation method based on the crowd flow control and the eddy current tuned mass damper to control the excessive vibration caused by the random crowd excitation. The vibration mitigation method is applied on an experimental footbridge under random crowd loads and then the mitigation performance is analyzed experimentally and numerically. The numerical method of the social force model is used to simulate pedestrians detour behaviour in a blocking scenario. The time-varying coupling model of the crowd-structure-tuned mass damper is established, and the structure response is investigated. A virtual three dimensional obstacle based on the pedestrian stereo vision on the laboratory footbridge is designed to avoid the accident that pedestrians may encounter caused by the actual obstacles. It was found that the numerical response is in an appropriate agreement with the experimental data, implying that the social force model can simulate the detour behaviour accurately. Finally, the mitigation strategies are numerically implemented on an indoor footbridge, and the factors influencing the vibration mitigation rate are further analyzed using three different layouts. The layouts include Layout 1, for forcing pedestrian diversion separation, and Layout 2, for generating a bottle neck effect, and Layout 3, a nonlinear layout mode of obstacles, which is a combination of Layouts 1 and 2. The results show that the performance of the proposed hybrid mitigation method is more effective than the single mitigation method. In addition, the results show that the number and layout of obstacles determine the mitigation efficiency. It was also found that the vibration mitigation rate of the hybrid method with Layout 3 increases with the crowd density and tends to be stable when the crowd density exceeds 0.92 ped./m2. In addition, the mixed layout scheme may have more advantages in controlling crowd motion under high crowd density, while the linear layout schemes have certain competitiveness under low crowd density.

Shaking table test and numerical simulation of eddy-current tuned mass damper for structural seismic control considering soil-structure interaction

This paper firstly investigates the vibration control performance of eddy current tuned mass damper (ECTMD) on structure considering soil-structure interaction (SSI) subjected to seismic loads, and shaking table tests of a six-story steel frame model equipped with ECTMD in SSI system are conducted. By comparison with the undamped TMD, the effectiveness of eddy current damping is also studied. The experimental results in the seismic cases clearly reveal that ECTMD mitigates the maximum displacement response both in rigid base and SSI situations, but it may amplify the peak floor acceleration considering SSI effects. On the whole, SSI decreases the mitigation effects of ECTMD on the structural maximum response, and eddy current damping can improve TMD’s control performance, especially in SSI system. Furthermore, a three-dimensional finite element model on the shaking table tests is established. The numerical model utilizes two different analysis procedures - equivalent linear method and bounding surface plasticity model, to simulate the nonlinear behavior of soil, and the concept of an equivalent eddy current damping is used to simulate ECTMD. A comparison of experimental and simulated results shows that the proposed model can accurately estimate the dynamic response of structure equipped with ECTMD in SSI system under earthquake excitations.

Wind Tunnel Study on Bidirectional Vibration Control of Lattice Towers with Omnidirectional Cantilever-Type Eddy Current TMD

An omnidirectional cantilever-type eddy current tuned mass damper (ECTMD) for lattice towers is introduced to suppress bidirectional vibration of lattice towers, in a form of a cantilever beam with a tip magnet mass. The damping of the ECTMD can be easily changed by tuning the amount of the current. A typhoon-fashion wind environment is simulated for the wind tunnel test. Test results show that there exists an optimal damping of the ECTMD along with an optimal frequency ratio. The scaled aeroelastic model is tested under various wind conditions, and a good effectiveness of ECTMD is observed. The wind directions, perpendicular and parallel to the cross-arm, are the most critical for the design of ECTMD, as the vibration mitigation in either of these two cases is relatively weaker. Finally, a simplified model is established for theoretical analysis in the frequency domain, whereby the variance responses of the tower with and without ECTMD are computed. The numerical results agree well with the experimental results, which corroborates the feasibility of using the proposed omnidirectional cantilever-type ECTMD in suppressing the vibrations of the tower in both along-wind and across-wind directions.

Influence of soil‐structure interaction on performance of a super tall building using a new eddy‐current tuned mass damper

SummaryTuned mass dampers (TMDs) can be used as vibration control devices to improve the vibration performance of high‐rise buildings. The Shanghai Tower (SHT) is a 632‐m high landmark building in China, featuring a new eddy‐current TMD. Special protective mechanisms have been adopted to prevent excessively large amplitude of the TMD under extreme wind or earthquake loading scenarios. This paper presents a methodology for simulating behavior of the new eddy‐current TMD that features displacement‐dependent damping behavior. The TMD model was built into the SHT finite element model to perform frequency analysis and detailed response analyses under wind and earthquake loads. Furthermore, soil‐structure interaction (SSI) effects on wind and seismic load responses of the SHT model were investigated, as SSI has a significant impact on the vibration performance of high‐rise buildings. It was found that SSI has more significant effects on acceleration response for wind loads with a short return period than for wind loads with a long return period. Some of the acceleration responses with SSI effects exceed design limits of human comfort for wind loads with shorter return periods. As to the seismic analyses, it was found that SSI slightly reduces the displacement amplitude, the damping force, and the impact force of the TMD.

Experimental and analytical study on vibration control effects of eddy-current tuned mass dampers under seismic excitations

Eddy-current tuned mass dampers (EC-TMDs) are non-contacting passive control devices and are developed on the basis of conventional tuned mass dampers. They comprise a solid mass, a stiffness element, and a damping element, wherein the damping mechanism originates from eddy currents. By relative motion between a non-magnetic conductive metal and a permanent magnet in a dynamic system, a time-varying magnetic field is induced in the conductor, thereby generating eddy currents. The eddy currents induce a magnetic field with opposite polarity, causing repulsive forces, i.e., damping forces. This technology can overcome the drawbacks of conventional tuned mass dampers, such as limited service life, deterioration of mechanical properties, and undesired additional stiffness. The experimental and analytical study of this system installed on a multi-degree-of-freedom structure is presented in this paper. A series of shaking table tests were conducted on a five-story steel-frame model with/without an EC-TMD to evaluate the effectiveness and performance of the EC-TMD in suppressing the vibration of the model under seismic excitations. The experimental results show that the EC-TMD can effectively reduce the displacement response, acceleration response, interstory drift ratio, and maximum strain of the columns under different earthquake excitations. Moreover, an analytical method was proposed on the basis of electromagnetic and structural dynamic theories. A comparison between the test and simulation results shows that the simulation method can be used to estimate the response of structures with an EC-TMD under earthquake excitations with acceptable accuracy.

Study on Adaptive-Passive and Semi-Active Eddy Current Tuned Mass Damper with Variable Damping

Tuned mass damper (TMD) is a widely used vibration control device, consisting of a mass, some springs and damping elements. Viscous damper is mostly used as a damping element; however, it has many unsustainable problems, e.g., poor durability, sensitive to the change of temperature, difficult to adjust the damping, oil leakage etc. In this paper, a new sustainable adaptive-passive eddy current tuned mass damper (ECTMD) with variable damping, which is very easy to be further upgraded to a semi-active one, is proposed. Four important parameters, e.g., adsorption position of permanent magnets, thickness of the conductive plate, thickness of the extra steel plate and the air gap between permanent magnets and the conductive plate are investigated by a parametric study. Two new evaluation indexes are put forward to indicate the damping mechanism of the proposed device. The relationship between effective damping coefficient and air gap is fitted through a quadratic function. Then, the corresponding design method of the proposed adaptive–passive ECTMD is presented. At last, the previous adaptive–passive ECTMD is upgraded to a semi-active one, which can adjust its eddy current damping through adjusting its air gap in real-time, based on the linear-quadratic-Gaussian algorithm. The effectiveness of semi-active ECTMD is evaluated through harmonic excitations and human-induced excitations. The results show that the semi-active ECTMD with variable damping has a better vibration control effect than the optimized passive one.

Experimental Study on Vibration Control of a Submerged Pipeline Model by Eddy Current Tuned Mass Damper

Undesirable vibrations occurring in undersea pipeline structures due to ocean currents may shorten the lifecycle of pipeline structures and even lead to their failure. Therefore, it is desirable to find a feasible and effective device to suppress the subsea vibration. Eddy current tuned mass damper (ECTMD), which employs the damping force generated by the relative movement of a non-magnetic conductive metal (such as copper or aluminum) through a magnetic field, is demonstrated to be an efficient way in structural vibration control. However, the feasibility and effectiveness of ECTMD in a seawater environment has not been reported on before. In this paper, an experiment is conducted to validate the feasibility of an eddy current damper in a seawater environment. A submerged pipeline is used as the controlled structure to experimentally study the effectiveness of ECTMD. The dynamic properties of the submerged pipeline are obtained from dynamic tests and the finite element method (FEM). The optimum design of TMD with a linear spring-damper element for a damped primary structure is carried out through numerical optimization procedures and is used to determine the optimal frequency tuning ratio and damping ratio of ECTMD. In addition, the performance of ECTMD to control the submerged pipeline model is respectively studied in free vibration case and forced vibration case. The results show that the damping provided by eddy current in a seawater environment is only slightly varied compared to that in an air environment. With the optimal ECTMD control, vibration response of the submerged pipeline is significantly decreased.

Experimental Study on Robustness of an Eddy Current-Tuned Mass Damper

In this paper, an eddy current tuned mass damper (ECTMD) is utilized to control the vibration of a cantilever beam. The robustness of the ECTMD against frequency detuning is experimentally studied in cases of both free vibration and forced vibration. The natural frequency of the cantilever beam can be adjusted by changing the location of a lumped mass. For purposes of comparison with the ECTMD, the robustness of a tuned mass damper (TMD) is also studied. The experimental results in the free vibration case indicate that the ECTMD works well both in tuned and detuned situations, and the equivalent damping ratio of the cantilever beam equipped with the ECTMD is 2.08~5.91 times that of the TMD. However, the TMD only suppresses the free vibration effectively in the tuned situation. With forced vibration, the experimental results also demonstrate the robustness of the ECTMD in vibration suppression in detuned cases. On the other hand, the cantilever beam with TMD experiences 1.63~2.99 times the peak vibration of that of the ECTMD control.

Invited Review: Recent developments in vibration control of building and bridge structures

This paper presents a state-of-the-art review of recent articles published on active, passive, semi-active and hybrid vibration control systems for structures under dynamic loadings primarily since 2013. Active control systems include active mass dampers, active tuned mass dampers, distributed mass dampers, and active tendon control. Passive systems include tuned mass dampers (TMD), particle TMD, tuned liquid particle damper, tuned liquid column damper (TLCD), eddy-current TMD, tuned mass generator, tuned-inerter dampers, magnetic negative stiffness device, resetting passive stiffness damper, re-entering shape memory alloy damper, viscous wall dampers, viscoelastic dampers, and friction dampers. Semi-active systems include tuned liquid damper with floating roof, resettable variable stiffness TMD, variable friction dampers, semi-active TMD, magnetorheological dampers, leverage-type stiffness controllable mass damper, semi-active friction tendon. Hybrid systems include shape memory alloys-liquid column damper, shape memory alloy-based damper, and TMD-high damping rubber.

Improving performance of a super tall building using a new eddy-current tuned mass damper

Two kinds of methods have been primarily used to improve the vibration performance of high-rise buildings. One approach is to enhance the structural lateral stiffness, which may increase the component size and inefficiently use material. The other approach is to employ vibration control devices, such as tuned mass dampers (TMDs), tuned liquid dampers (TLD) and other supplemental damping devices. This latter approach has proved to be quite economical and efficient, and as such, increasingly used in practice. The Shanghai Center Tower (SHC) is a super high-rise landmark building in China, with a height of 632 m. In order to mitigate its vibration during wind storms, a new eddy-current TMD was installed at the 125th floor. Special protective mechanisms were incorporated to prevent excessively large amplitude motion of the TMD under extreme wind or earthquake scenarios. Results of reduced-scale laboratory tests and field tests are presented in this paper to characterize the dynamic properties of the damping device and validate the fidelity of the numerical results. Results of structural analyses indicate that for SHC the eddy-current TMD was able to reduce wind-induced structural acceleration by 45%–60% and earthquake-induced structural displacement by 5%–15%. The installation of the TMD was completed in December 2014, and the performance observed to date is judged to be good. Copyright © 2016 John Wiley & Sons, Ltd.

Control of Human-Induced Vibrations of a Curved Cable-Stayed Bridge: Design, Implementation, and Field Validation

AbstractThis article describes the research work relating to the assessment and control of human-induced vibration of an unusual curved cable-stayed bridge with separate road and pedestrian decks. Dynamic simulations of human-induced vibration were performed with a mode-by-mode approach, and the results showed that a total of eight lateral and vertical modes of the bridge may suffer from excessive vibrations at the design crowd density. A hybrid control scheme was developed for control of human-induced vibration, which consists of steel braces fitted between the road bridge deck and the pedestrian deck to improve structural stiffness and eddy current tuned mass dampers to enhance damping ratios of lively modes. The modal properties of the bridge with steel braces were experimentally obtained by dynamic tests and used for parameter tuning of mass dampers. The performance of the hybrid control strategy was evaluated by group tests of up to 400 pedestrians. It is shown that the critical number of pedestrians...

Study on TMD Measure to Suppress Wind-Induced Vibration of Power Transmission Steel Tower

Wind-induced vibration can affect the safety of power transmission tower. Vibration suppression of the high-rise tower is of concern in engineering. Vibration of the tower is mostly the first-order bending modal and this vibration can be suppressed by the tuned mass damper (TMD). This paper developed a TMD vibration damping device using eddy current damper constituted by magnetic steel installed in the vibration mass and fixed copper plate. It is characterized by simple structure and easy installation, and is suitable for wind-induced damage prevention of transmission tower. Focusing on a quadruple-circuit on the same steel tube tower, a vibration reduction test on a real-scale tower conducted. The result shows that the damping ratio of the tower after installed with the TMD device will increase about 3%. The actual test result verifies the effectiveness of the eddy current TMD device.