Inertia Damping Research Articles

Influence of spatially varying ground motions on the seismic responses of adjacent bridges coupled by a tuned inerter damper

Recently, the authors explored the effectiveness of using an inerter-based device to mitigate pounding induced damage between two adjacent bridge structures, and the advantages of this system were illustrated by comparing its performances with the conventional viscous dampers. However, the seismic excitations at the supports of the adjacent bridge structures were assumed to be the same in that study, i.e. only uniform ground motion was considered. In reality, ground motions at different locations of a structure are inevitably different, and spatially varying ground motions (SVGMs) can influence the structural seismic responses significantly. Extensive research works have been carried out to investigate the influence of SVGMs on the seismic responses of engineering structures. However, no open literature reported the results when an inerter-based device is involved. In this study, the motion equations of two adjacent bridges coupled by a tuned inerter damper (TID) are firstly derived, and the seismic responses of the adjacent bridges with and without control are calculated. In particular, the parameters that significantly influence SVGMs, i.e. wave passage effect and coherency loss effect, are discussed.

Force Optimization and Damping Performance of a Novel Ferrofluid Inertial Damper Based on the Levitation Principle of Ferrofluids

Force Optimization and Damping Performance of a Novel Ferrofluid Inertial Damper Based on the Levitation Principle of Ferrofluids

Tuning methods for tuned inerter dampers coupled to nonlinear primary systems

Tuning methods for tuned inerter dampers coupled to nonlinear primary systems

Seismic response control of base-isolated structures with fluid inerter damper

Seismic response control of base-isolated structures with fluid inerter damper

Geometrically nonlinearity analysis and performance evaluation of tuned inerter dampers for multidirectional seismic isolation

Tuned inerter dampers (TIDs) have been widely studied for vibration control and seismic isolation. It is traditionally mounted in the direction of motion of the primary structures and mitigate only the vibration in the direction of mounted. In this study, a configuration of geometrically nonlinear TID (GNTID) is investigated for multidirectional seismic isolation of structures. The GNTID is set up in perpendicular to the motion of a primary structure, and generates a force which is nonlinear with respect to the motion of the structure. The dynamic response of a SDOF system with GNTID under harmonic excitation is obtained via the method of incremental harmonic balance, followed by a stability analysis to establish the unstable diagram of excitation amplitude and frequency. The optimal parameters of GNTID are derived by minimizing the absolute displacement transmissibility. By applying a sequence of curve fitting scheme, design formula for optimal tuning parameters of the GNTID are formulated which are expressed as functions of structural damping ratio, inertance-mass ratio for various excitation amplitude. Finally, two examples are given to demonstrate the vibration isolation performance of GNTID. The maximum transmissibility of the GNTID system is smaller compared with uncontrolled system, and it has wider vibration isolation frequency band. In addition, the application of GNTID in the base-isolated structure can significantly reduce the peak value of seismic response and realize multidirectional vibration isolation.

Global Simultaneous Optimization of Oil, Hysteretic and Inertial Dampers Using Real-Valued Genetic Algorithm and Local Search

A method for global simultaneous optimization of oil, hysteretic and inertial dampers is proposed for building structures using a real-valued genetic algorithm and local search. Oil dampers has the property that they can reduce both displacement and acceleration without significant change of natural frequencies and hysteretic dampers possess the characteristic that they can absorb energy efficiently and reduce displacement effectively in compensation for the increase of acceleration. On the other hand, inertial dampers can change (prolong) the natural periods with negative stiffness and reduce the effective input and the maximum acceleration in compensation for the increase of deformation. By using the proposed simultaneous optimization method, structural designers can select the best choice of these three dampers from the viewpoints of cost and performance indices (displacement, acceleration). For attaining the global optimal solution which cannot be attained by the conventional sensitivity-based approach, a method including a real-valued genetic algorithm and local search is devised. In the first stage, a real-valued genetic algorithm is used for searching an approximate global optimal solution. Then a local search procedure is activated for enhancing the optimal character of the solutions by reducing the total quantity of three types of dampers. It is demonstrated that a better design from the viewpoint of global optimality can be obtained by the proposed method and the preference of damper selection strongly depends on the design target (displacement, acceleration). Finally, a multi-objective optimization for the minimum deformation and acceleration is investigated.

Parameters optimization and performance evaluation for the novel tuned inertial damper

This paper presents a double-flywheels architecture for a novel tuned inertial damper with grounded stiffness device acts as a passive vibration absorber. An undamped primary structure model with a single degree of freedom controlled by the proposed tuned inertial damper is developed and used to derive the equations of motion of the coupled system. The optimum frequency ratio and the optimum damping ratio are found based on the fixed points theory under harmonic force-excited primary structure. Then, the optimum grounded stiffness ratio is deduced. According to the change on the system parameters, there are three cases for the optimum grounded stiffness ratio, i.e., negative, zero and positive. It is found that from these three cases, the proposed tuned inertial damper with positive grounded stiffness device has the best control performance. When compared with some existing dynamic vibration absorbers, the proposed model in this paper in three cases presented the best control performance, featured by the broadest suppression bandwidth and the minimal vibration amplitude of vibration reduction effect under harmonic and random excitation.

FxLMS Algorithm for Active Vibration Control of Structure By Using Inertial Damper with Displacement Constraint

Engine is the main source of vibration that generates unwanted noise and vibration of vehicle chassis. Especially, in submarine applications, radiation of noise signatures can be detected at some distance away from the submarine using a sonar array. Thus quiet operation is crucial for submarine’s survivability. This study addresses reduction of the force transmissibility originating from engines and transmitted to hull through engine mounts. An inertial damper, as an actuator of hybrid mount system, is addressed to reduce even further the level of vibration. Narrow band FxLMS algorithms are broadly used to cancel the vibration of engine mount because of its excellent performance of canceling narrow band noise. However, in real active dampers, the maximum displacement of damper mass is kinematically restricted. When the control input signal from the FxLMS algorithm exceeds this limitation, the damper mass will collide with the mechanical stops and results in many problems. Originated from these, a modified narrow band FxLMS algorithm based on the equalizer technique with the maximum allowable displacement of active damper mass is proposed in this study. Some simulation results showed that the propose algorithm is effective to suppress vibration of engine mount while ensuring given displacement constraint.

Design and Investigation of a Nonlinear Damper Based on Energy Dissipation through Shock and Dry Friction to Suppress Critical Self-Excited Vibrations in Drilling Systems

In this paper, a passive damper based on energy dissipation through shock and dry friction (shock-friction damper) is investigated regarding its design and effectiveness for damping self-excited torsional vibrations similar to those occurring in deep drilling. The results are compared to the results of conventional friction dampers. The effectiveness of the damper for different operational drilling parameters that change during the drilling process, such as the weight on the bit and the rotary speed of the bit, is analyzed. Two linear reduced order models of a drill string that are based on a complex finite element model are set up. One is reduced using the component mode synthesis and one is reduced to the identified critical mode. A lumped mass represents the inertia of a forcedly connected nonlinear damper. A combined reduced order model of the complex system and the inertia damper is introduced to investigate its dynamic motion and stability. Particular focus is on the energy flow within the dynamic system and on the change of the dissipation energy in the contact. A semi-analytical solution is derived using the harmonic balance method that is used to investigate the damping effect for various designs and operational parameters. Herein, the modal properties as well as parameters of the damper are examined regarding the damping effect and the stability of the system. Finally, the capability of the mechanism to suppress the self-excitation due to the bit–rock interaction in a drilling system is discussed, and recommendations are made with respect to the design parameters and placement of the damper.

Transition state dynamics of a driven magnetic free layer

Magnetization switching in ferromagnetic structures is an important process for technical applications such as data storage in spintronics, and therefore the determination of the corresponding switching rates becomes essential. We investigate a free-layer system in an oscillating external magnetic field resulting in an additional torque on the spin. The magnetization dynamics including inertial damping can be described by the phenomenological Gilbert equation. The magnetization switching between the two stable orientations on the sphere then requires the crossing of a potential region characterized by a moving rank-1 saddle. We adopt and apply recent extensions of transition state theory for driven systems to compute both the time-dependent and average switching rates of the activated spin system in the saddle region.

Generalized optimal design of multiple tuned inerter dampers for control of MDOF structures under stochastic seismic excitation

Generalized optimal design of multiple tuned inerter dampers for control of MDOF structures under stochastic seismic excitation

Seismic response control of adjacent buildings using optimal backward-shared tuned mass damper inerter and optimal backward-shared tuned inerter damper

Seismic response control of adjacent buildings using optimal backward-shared tuned mass damper inerter and optimal backward-shared tuned inerter damper

Multiple tuned inerter-based dampers for seismic response mitigation of continuous girder bridges

Tuned inerter-based dampers (TIBDs), such as the tuned viscous mass damper (TVMD) and tuned inerter damper (TID), have demonstrated better control performance compared with traditional dampers. To enhance the seismic performance of continuous girder bridges, multiple TIBDs are employed to protect the long-span high-speed railway (HSR) continuous girder bridges under the seismic excitation. The governing equations of the motion of the bridge with TIBDs are reformulated in state-space. Based on the H2 control strategy, the frequency ratio and damping ratio of TIBDs to tune multiple modes of bridges are optimized. The control performance of TIBDs with optimal parameters is evaluated and compared with that of the viscous dampers (VDs) in terms of mitigating the peak response and root mean square (RMS) response of the bridge. Meanwhile, through analyzing the power spectral density and dissipated energy of different dampers, the mitigation principle of TIBDs is explored. Results show that TIBDs with optimal parameters can effectively improve seismic performance of the long-span HSR continuous girder bridge. Nevertheless, VDs shows better effectiveness of vibration mitigation on some seismic responses at large inertance ratio in the transverse direction. In addition, the control efficiency of seismic mitigation is reduced for optimal TIBD compared with that for VD with the increase of inertance ratio. Note that the non-linear behavior of the ballasted track system for used HSR bridge model is not considered in the study. Therefore, the proposed analysis method and results obtained in this study can provide references for seismic response control in the linear continuous girder bridges using multiple TIBDs.

Experimental study on active tuned inerter-dampers: Application to active damping using force feedback

In this paper, a modified active tuned inerter damper concept which is more suitable for practical applications is proposed. The proposed device is composed of a pair of collocated reactive actuator and force sensor. A second-order low-pass filter and a proportional term are combined to form the controller. The equivalent mechanical model of the controller's components is derived in order to better interpret the coupled system. The second-order low-pass filter is mechanically equivalent to a pure mechanical network which comprises an inerter, a spring and a damper connected in parallel. The proportional term mechanically represents a spring which is connected in series with the inherent actuator spring. Simple regressions are derived based on the ℍ∞ optimisation criterion wherein the optimal feedback gains are calculated to minimise the maximal response of the driving-point receptance of the system. The numerical study is also experimentally validated. The obtained results are found to correspond well with the theoretical developments.

Inerter dampers with linear hysteretic damping for cable vibration control

Long stay cables in cable-stayed bridges have low and close-spaced modal frequencies and are subjected to multimode vibrations, e.g., rain–wind vibrations and vortex-induced vibrations. Many types of dampers used in practice for cable vibration control can be described using a linear hysteretic damping model, e.g., high-damping rubber dampers and viscous-shear dampers. Such dampers are able to provide frequency-independent damping effects while the maximal achievable damping is limited due to their intrinsic stiffness effect. Therefore, this study investigates dampers with linear hysteretic damping enhanced by inerters for cable vibration control. A general inerter damper, consisting of a spring with complex stiffness and an inerter in parallel which is then connected to another inerter in series, is attached to a cable for dynamic analyses. Complex modal analysis is performed to appreciate cable damping. The optimal damping effect is discussed with reference to dynamic properties of the damper with respect to frequency, with comparison to the system of a cable with an inerter damper with viscous damping. It is found that two inerters, respectively in parallel and in series with a damper of linear hysteretic damping, can achieve a large improvement on multimode damping of a cable. The inertance of the inerter in series with the damper needs to be large for optimal performance while a small inertance of the other inerter is preferable. Furthermore, a case study based on a cable attached with a viscous-shear damper on the Sutong Bridge is conducted to show the feasibility of the inerter dampers.

Wave flume tests of a semi-submersible platform controlled by a novel rotational inertia damper

Semi-submersible platforms (SSPs) may subject to excessive wave-induced vibrations, which should be effectively suppressed. In the past decades, some vibration control methods have been proposed and developed, such as the fixed heave plate (FHP) and tuned heave plate (THP). Recently, the authors proposed using inerter-based control device, i.e. rotational inertia dampers (RIDs), to control the vibrations of SSPs, and the control effectiveness has been demonstrated through analytical studies. To further investigate the feasibility and effectiveness of the proposed method, wave flume tests are conducted and reported in the present study. In particular, a 1:70 scaled SSP model was manufactured, and the vibration characteristics of the platform were determined firstly through free vibration tests. After that, the bare and RID equipped SSPs were tested under the regular and irregular waves. For comparison, the SSP equipped with the commonly used FHP was also tested. The experimental results demonstrate that both the RID and FHP systems are effective in reducing the heave motion of SSP. However, compared to the FHP, the RID system showed a much better control performance with a very small physical mass. The wave flume tests demonstrated the superior vibration control performances of RID on SSP.

Prototype Test and Numerical Analysis of a Shallow Cable with Novel Viscous Inertial Damper

As an essential component of offshore bridges, stay cables are prone to vibrations due to their low inherent damping characteristics. Various dampers have been used for cable vibration control; however, the experimental research and theoretical study of inertial dampers on real cables have not been conducted sufficiently. This study aims to investigate the damping performance of a novel viscous inertial damper (VID) and focuses on the frequency-dependent and displacement amplification phenomena of a cable-damper system. Tests were first conducted to verify the energy consumption capacity of a prototype damper. A shallow cable-VID system was established. Theoretically, complex-valued modes were analyzed to determine the influence of the inertial and viscous coefficients on the cable’s frequency and mode damping ratio. The test results and numerical analysis show that the VID has a good damping effect on the shallow cable. Considering multiple adjacent cable modes, the inertial and viscous coefficients can be optimized. After optimizing, the VID can simultaneously maximize both adjacent symmetric and antisymmetric modes’ damping ratios. The two frequencies are almost the same. The displacement amplification of the VID shows that a VID can overcome the shortcomings of displacement loss caused by traditional oil dampers. The implications of these findings of the VID on shallow cable are discussed, which will guide future research and applications of the VID or other inerter dampers.

A new approach to inertial damper design to control base displacement in isolated buildings

A novel design procedure for tuned mass dampers in isolated structures is presented. The proposed optimization method is specifically developed to control base displacements or to solve the large isolator displacement problem in this type of structures under earthquakes. Therefore, it is based on a displacement transmissibility function, T, a particular case of the general transmissibility concept, which comes from Vibration Isolation. Three contributions are: 1) application of new seismic displacement narrowbandness, 2) simpler relative transmissibility function, and 3) compound design of isolation plus tuned mass damper. A standard isolated model is used to show that the base displacement can be controlled at levels in the proximity of the ground motion (T ≈ 1), which results in a positive comparison with previous isolation plus tuned mass damper solutions; this is one of the main conclusions and it is based on novelty 3 above; in fact, other solutions in the literature compare their attained displacements with respect to the structure without tuned mass damper. Comparison with isolated results is not, therefore, possible herein, but it is not desirable either; actually, what is possible is a positive and more demanding comparison, which is with respect to the very seismic ground displacement itself. The large isolator displacement problem can be solved or attenuated by properly designing a tuned mass damper subsystem jointly with the isolation one.

Optimal design of dual isolated structure with supplemental tuned inerter damper based on performance requirements

This paper investigated the use of tuned inerter damper (TID) to enhance the seismic performance of dual isolated structure (DIS). An optimization design strategy was developed based on the performance requirements and expressed as a constrained multi-objective optimization design problem, where by the displacement response ratios of isolation layers were adopted as the constraints, and the acceleration response ratio of the superstructure was selected as the objective function. Meanwhile, the time history analysis was conducted to verify the effectiveness of the optimization strategy. The results indicated that the proposed dual isolated structure could effectively decrease the displacement of the superstructure relative to the ground; furthermore, it reduces the isolation layers' deformations compared with the DIS and the base isolated structure (BIS).

Vibration control of beam-model using tuned inerter enhanced TMD

Two vibration control devices using the tuned inerter enhanced TMD are introduced to suppress the vibration of Euler–Bernoulli beam-model in this paper. The two tuned inerter enhanced TMD systems are improved on the basis of the classical TMD system by replacing its damper element with the newly developed tuned viscous mass damper (TVMD) and tuned inerter damper (TID), respectively. The equations of motion and frequency response function of the beam-model subjected to harmonic excitation are derived by the theory of Euler–Bernoulli beam-model. Moreover, the H∞ optimization technique and the extended fixed-points theory are employed to obtain the optimal parameters and closed-form solutions of TVMD and TID enhanced TMD systems, and the control performance of two enhanced systems is analyzed compared with the TMD system. The results reveal that TVMD and TID enhanced TMD systems have stronger robustness and wider control range for the resonance response. Furthermore, the enhanced systems have higher control effectiveness at a small mass ratio compared with the TMD system. Finally, the effectiveness of the enhanced systems is verified by a numerical study considering the harmonic and band-limited white noise excitations.