Vibration Mitigation Of Structures Research Articles

An Active Nonlinear Controller Emulating a Pendulum-Type Auto-parametric Vibration Absorber

In this paper, a nonlinear active vibration control method, which is suitable for the vibration mitigation of both linear and nonlinear structures, is proposed. The main idea of this method is to make the controller emulate a pendulum-type auto-parametric vibration absorber, with the purpose of counteracting the different types of nonlinearity in structures. In this way, the difficulty in the passive realization of the pendulum-type vibration absorber due to the physical unsuitable parameters can also be well released. The idea of introducing an exosystem in Byrnes–Isidori regulator is borrowed to design the nonlinear controller. The steps to choose the parameters of the controller are introduced. The validity and robustness of the controller for the vibration mitigation of both linear and nonlinear oscillators are investigated by numerical examples of application. The simulation results show that the proposed nonlinear controller can effectively mitigate the vibration not only of linear oscillators, but also of nonlinear oscillators with third-, quintic- and seventh-order nonlinearities. The good robustness of the proposed nonlinear controller is also demonstrated.

A particle inerter system for structural seismic response mitigation

This study introduces a novel particle inerter system (PIS) designed for vibration mitigation of structures. The new system comprises an inerter subsystem, a spring, and a tuned particle element, where the spring is used for tuning the particle element and the inerter subsystem is set for energy absorption and dissipation. The structural performance and the vibration mitigation effect of the PIS are assessed in terms of displacement and acceleration responses. An optimal design method is developed for a PIS under a performance-oriented design framework. Following the criterion of lightweight control, the added mass of the PIS is minimized under the constraints of target displacement and acceleration responses. A parametric analysis is performed and the robustness of the PIS for seismic response mitigation is verified. Design cases are carried out for the illustration of the proposed design method. The results show that the structural displacement and acceleration responses can be reduced significantly with the help of a PIS. Compared with the particle tuned mass damper with the same parameters, both the energy absorption and dissipation effects of the PIS are increased and the relative displacement response of the container in the PIS is reduced by the inerter subsystem. Under the same performance target, the required physical mass of the container and particles in the PIS is minimized and is significantly smaller than that of the conventional particle tuned mass damper.

Experimental study of vibration mitigation of mast arm signal structures with particle-thrust damping based tuned mass damper

Large amplitude vibration of mast arm structures due to wind loads are the primary contributing factor to the reduced fatigue life of signal support structures. To alleviate this problem of wind-induced in-plane vibration of mast arm signal structures, a particle-thrust damping based turned mass damper (PTD-TMD) device is adopted and its damping effect is characterized experimentally. The particle-thrust damping is a passive damping device that does not require electric power and is temperature independent. Based on the calibration test, an equivalent dynamic model of the PTD-TMD device is developed and used for numerical simulation study. The damping effects of this PTD-TMD device on signal support structures was investigated through both numerical analysis and laboratory testing of a 50-ft (15.24 m) mast arm structure including both free vibration and forced vibration tests. The experimental test and numerical study results show that vibration response behavior of mast arm signal support structures can be significantly reduced by installing the PTD-TMD that can increase the critical damping ratio of the mast arm signal structures to 4%. The stress range at the welded connection between the mast arm and traffic pole is also reduced.

Study on a magnetorheological elastomer-base device for offshore platform vibration control

Wave loading is one of the leading factors contributing to fatigue damage of offshore platforms. Vibrations in marine platforms due to nonlinear hydrodynamic forces can reduce platform productivity, endanger safety, and affect serviceability. This article presents numerical evaluation of a magnetorheological elastomer device for wave-induced vibration reduction of offshore platform. Random wave loadings are estimated by wave spectrum analysis and Morison’s equations. By altering field-induced stiffness of magnetorheological elastomers and non-resonance control strategy, the wave-induced vibration of offshore platform is effectively reduced, and the magnetorheological elastomer device presents strong control robustness under various wave loadings. This work indicates that magnetorheological elastomer-base device may open a new insight for vibration mitigation of ocean structures.

Performance of natural rubber and silicone-based magnetorheological elastomers under large-strain combined axial and shear loading

This study presents an experimental investigation on large-strain behavior of natural rubber– and silicone-based magnetorheological elastomers within a larger scope of structural vibration mitigation due to wind, traffic and seismic events. Magnetorheological elastomer samples with different weight percentages of iron particles, additives, and elastomer matrix were fabricated. The microstructures of specimens were examined, and their mechanical properties were investigated by a unique electromagnetic double-lap shear experimental setup capable of applying simultaneous compression and shear loads. The experimental results demonstrated that the isotropic natural rubber–based magnetorheological elastomers exhibit about 30% magnetorheological effect under large strains, while they achieve a higher magnetorheological effect under the combined axial and shear loading. The magnetorheological effect was 92% and 33% for 10% and 100% shear strains when 100 psi axial stress was applied. A natural rubber–based magnetorheological elastomer was further investigated applying dynamic cyclic load with and without compression load for different strains, frequencies, and magnetic field intensities. It was observed that for higher frequency, magnetorheological effect was reduced. Magnetorheological effects were 73% and 29% for 0.1 and 10 Hz frequencies, respectively, under 100 psi axial stress at 150% shear strain. The result of this study suggests that isotropic natural rubber–based magnetorheological elastomers may be suitable for high-demand-force applications, and in particular, in civil structures.

Thermally tunable band gaps in architected metamaterial structures

The combined characteristics of periodic and locally resonant features in metamaterial structures, or meta-structures, give rise to unique wave propagation characteristics such as relatively low and wide band gaps. These meta-structures have a fixed geometry and thus a fixed behavior, however applications that require structural vibration mitigation such as spacecraft and automotive components have variable vibration mitigation requirements over a range of operation and external conditions. In this paper, we propose a method to thermally tune the band gaps of composite meta-structures, which combine a periodic lattice and locally-resonant inclusions, through changes in temperature of the structure. The concept primarily takes advantage of the different moduli of the two materials in the meta-structure that have drastically different temperature dependences, to preferentially tune the modulus of the lattice material compared to the resonant inclusion. We introduce an additional concept, termed thermal partitioning, to partially or fully open and close band gaps by locally controlling the temperature within the meta-structure. We demonstrate these results numerically with finite element simulations.

Semi-active phase control of tuned mass dampers for translational and torsional vibration mitigation of structures

The present study aims at demonstrating the feasibility of semi-active phase control of tuned mass dampers (TMDs) implemented in structures for simultaneous reduction in translational and torsional vibration. The semi-active phase control, which employs a semi-active friction device, applies the friction force at certain situations to adjust the TMD phase back to the 90° phase lag. Thus, the phase control tuned mass dampers (PC-TMDs) can develop the best power flow to reduce the structural vibration. In this paper, a complete phase control algorithm is proposed by considering a full range of phase differences. The proposed PC-TMDs not only improve the control performance but also prevent the TMD power from flowing back to the main structure. Furthermore, conventional suspension-type TMDs have only one tuning frequency and exhibit a potential off-tuning issue, lacking an ability to simultaneously suppress the structural translational and torsional vibration. The feasibility of application of the PC-TMDs is verified through various numerical simulations, and a practical mechanism for the PC-TMDs is introduced. The simulation results reveal the robustness of the PC-TMDs, particularly when the PC-TMDs are de-tuned to the structure. Therefore, the PC-TMDs outperform the conventional TMDs in terms of suppressing the structural responses in all the translational and torsional directions.

Experimental study on a new damping device for mitigation of structural vibrations under harmonic excitation

This manuscript introduces a new damping device which is composed of a water tank and a pendulum. The new damping device can be tuned to multiple frequencies. In addition, it has a higher energy dissipation capacity when compared with the conventional Tuned Liquid Dampers (TLDs). In order to evaluate the efficiency of this new damping device a series of free vibration and forced vibration tests were conducted on a scaled down single-story one-bay steel frame. Two different configurations were studied for the mass of the pendulum that included a completely and a partially submerged mass. It was observed that the completely submerged configuration led to 44% higher damping ratio when compared with the conventional TLD. In addition, the completely submerged configuration reduced the peak displacement response of the structure 1.6 times more than the conventional TLD. The peak acceleration response of the structure equipped with the new damping device was reduced twice more than the conventional TLD. It was also found that, when the excitation frequency is lower than the resonance frequency, the conventional TLD performs better than the partially submerged configuration of the new damping device.

A GBMO-based PI λ D μ controller for vibration mitigation of seismic-excited structures

The advantages of fractional-order proportional–integral–derivative (FOPID) controllers in terms of flexibility, robustness against model uncertainties and good disturbance rejection, are good motivations to use them for vibration mitigation of seismic-excited structures. The application of the FOPID controller for adjusting the control force of an active tuned mass damper (ATMD) for seismic control a building is studied in this paper. Gases Brownian motion optimization (GBMO) algorithm is employed for optimal tuning of parameters of the FOPID and PID controllers. Evaluation of the frequency responses of the structure for uncontrolled and controlled cases shows that PID and FOPID controllers are very effective for the seismic control of structures. For further investigation, the performance of the FOPID controller in the reduction of seismic responses of the building in four well-known earthquake excitations is compared with those provided by the PID, linear–quadratic regulator (LQR) and fuzzy logic control (FLC). Simulation results show that the PID and LQR controllers provide the same performance in reducing the maximum top floor displacement of the structure. Moreover, the FLC and FOPID controllers demonstrate a superior performance in seismic control of the structure. The FLC is able to reduce the maximum displacements of all stories for all studied earthquakes. However, the proposed FOPID controller is able to provide a better performance in comparison with the FLC. In average, the FOPID controller mitigates the seismic responses of the structure as much as 29%, 27% and 15% better than the LQR, PID controller and FLC.

Parameter identification of modified Bouc–Wen model and analysis of size effect of magnetorheological dampers

Magnetorheological damper is one of the most promising smart devices for vibration mitigation of structures subjected to dynamic loads. In order to fulfill the value of magnetorheological damping control, a feasible mechanical model of magnetorheological dampers with simplicity and sufficient accuracy is usually required in practice. It comes up, however, with a challenging issue for the modeling of large-size magnetorheological dampers due to physical constraints on the performance test. The large-size magnetorheological damper is typically modeled in up-scaling parameters associated with models of the small-size magnetorheological damper. This treatment remains open since a size effect hinges upon the intrinsic non-linearity inherent in the device. In this article, a dynamic test of a small-size magnetorheological damper is performed first. The relevance of damper force with the input current and excitation frequency is well revealed. The modified Bouc–Wen model is employed to logically represent the dynamic behaviors of magnetorheological dampers. Identification of model parameters in typical loading cases is then proceeded, of which the functional relationship against input current is established. The size effect of magnetorheological dampers is further addressed through investigating the functional relationship relevant to maximum outputs of 200, 10, and 5 kN. It is indicated that the small-size magnetorheological damper needs more number of control parameters than the large-size magnetorheological damper. Moreover, a linear current relevance of model parameters appears in the small-size magnetorheological damper, while a quadratic current relevance of model parameters appears in the large-size magnetorheological damper. Size effect of magnetorheological dampers arises to be well-marked in the range of low current and becomes unapparent in the range of high current. Besides, the validation of modified Bouc–Wen model is carried out that reveals the applicability of the model with case-optimized parameters.

Modeling, Design Optimization, and Verifications of Permanent Magnet Linear Actuators for Structural Vibration Mitigation Applications

Structural vibrations in modern buildings have been increasing concerns. If not properly controlled, they would give rise to serviceability problems and disturbances to occupants. The permanent magnet (PM) linear actuator-based active vibration mitigation strategy exhibits excellent dynamic performances on elimination of vibrations with complex modes, and has great potential. This paper describes modeling, design optimization, and numerical and experimental verifications of a PM linear actuator for structural vibration mitigation applications. Analytical expressions for prediction of the actuator performance are derived, and the linear actuator is then designed in optimization within a specific set of volumetric and thermal constraints in order to maximize the product of efficiency and power factor. It is shown that the proposed analytical model has provided a computationally efficient tool for design optimization, and the Halbach ratio and actuator width have significant impacts on the performance of the PM linear actuator. The results are validated by finite-element computations, and further verified by experimental measurements on a prototype actuator.

Probabilistic analysis of wind-induced vibration mitigation of structures by fluid viscous dampers

The high-rise buildings usually suffer from excessively large wind-induced vibrations, and thus vibration control systems might be necessary. Fluid viscous dampers (FVDs) with nonlinear power law against velocity are widely employed. With the transition of design method from traditional frequency domain approaches to more refined direct time domain approaches, the difficulty of time integration of these systems occurs sometimes. In the present paper, firstly the underlying reason of the difficulty is revealed by identifying that the equations of motion of high-rise buildings installed with FVDs are sometimes stiff differential equations. Thus, an approach effective for stiff differential systems, i.e., the backward difference formula (BDF), is then introduced, and verified to be effective for the equation of motion of wind-induced vibration controlled systems. Comparative studies are performed among some methods, including the Newmark method, KR-alpha method, energy-based linearization method and the statistical linearization method. Based on the above results, a 20-story steel frame structure is taken as a practical example. Particularly, the randomness of structural parameters and of wind loading input is emphasized. The extreme values of the responses are examined, showing the effectiveness of the proposed approach, and also necessitating the refined probabilistic analysis in the design of wind-induced vibration mitigation systems.

Performances of Various Base Isolation Systems in Mitigation of Structural Vibration Due to Underground Blast Induced Ground Motion

A comparative study is carried out on the performance of various elastomeric and frictional base isolation (BI) systems in the vibration mitigation of structures subjected to underground blast induced ground motion (BIGM). The parametric sensitivities of the base isolated structures to variations in the design parameters of the isolators are examined for different intensities of blast input. Results indicate that substantial reductions in both the acceleration and displacement responses of the structure can be achieved by the different base isolators. Generally, the Electricite de France (EDF) base isolator produces higher peak response reductions. However, peak bearing displacements are also largest here. The pure friction (P-F), resilient-friction base isolator (R-FBI) and friction pendulum (FP) systems produce lower values of response reductions but peak bearing displacements as well as residual displacements of isolators are also low. The New Zealand (N-Z) system provides good response reductions with a low to moderate value of peak bearing displacement. The present study indicates how a proper selection of the type of BI system with suitable design parameters can mitigate structural vibration due to different intensities of BIGM and restrict the unwanted characteristics of large isolator displacement and its permanent deformation.

Fractional order PID control design for semi-active control of smart base-isolated structures: A multi-objective cuckoo search approach

Fractional order PID (FOPID) controllers are introduced as a general form of classical PID controllers using fractional calculus. As this controller provides good disturbance rejection and is robust against plant uncertainties it is appropriate for the vibration mitigation in structures. In this paper, an FOPID controller is designed to adjust the contact force of piezoelectric friction dampers for semi-active control of base-isolated structures during far-field and near-field earthquake excitations. A multi-objective cuckoo search algorithm is employed to tune the controller parameters. Considering the resulting Pareto optimal front, the best input for the FOPID controller is selected. For seven pairs of earthquakes and nine performance indices, the performance of the proposed controller is compared with those provided by several well-known control techniques. According to the simulation results, the proposed controller performs better than other controllers in terms of simultaneous reduction of the maximum base displacement and story acceleration for various types of earthquakes. Also, it provides acceptable responses in terms of inter-story drifts, root mean square of base displacements and floor acceleration. In addition, the evaluation of robustness for a stiffness uncertainty of ±10% indicates that the proposed controller gives a robust performance against such modeling errors.

Preliminary results and simulation of an active pendulum system for a three floor building

The mitigation of vibrations caused by seismic events has been a long term interest of structural control engineers in their effort to ensure the protection of both civil structures and human occupants. Several control strategies have been used as active vibration suppression methods, especially optimal control strategies such as the linear quadratic regulator. In this paper, a fractional order linear quadratic regulator is designed to cope with the disturbances that may occur in civil structures in the event of an earthquake. The case study consists in a three floor structure equipped with sensors and an active pendulum system to suppress unwanted vibrations. The simulation results show that the proposed controller can effectively achieve the mitigation of structural vibrations.

Hybrid Semi-Active Mass Dampers in Structures; Assessing and Optimising Their Damping Capacity

The paper discusses the “software”-optimisation of a novel, energy-, cost- efficient hybrid semi-active tuned mass damper configuration applicable to earthquake and wind structural vibration mitigation. Namely, an arrangement of both active and semiactive vibration control components coupled with a range of practical-to-use control algorithms are assessed towards an optimal and fail-safe holistic solution. For brevity, the testbed is the simplest sway single-degree-of-freedom structure under harmonic loading. The analysis for the hybrid vibration mitigation device builds on top of previous findings on the effects of control constraints, such as the stroke and force saturation limits, on the effective structural damping performance. The outcome produced is a hyperstable control solution that while waiving the cumbersome requirement for full-state feedback enables superior performance both in terms of response and energy demand. Essentially such an option satisfies both strict serviceability and sustainability requirements that are often found to govern modern structural applications, yielding a practical, reliable option with broad applicability and efficiency.

MR Damper Controlled Vibration Absorber for Enhanced Mitigation of Harmonic Vibrations

This paper describes a semi-active vibration absorber (SVA) concept based on a real-time controlled magnetorheological damper (MR-SVA) for the enhanced mitigation of structural vibrations due to harmonic disturbing forces. The force of the MR damper is controlled in real-time to generate the frequency and damping controls according to the behaviour of the undamped vibration absorber for the actual frequency of vibration. As stiffness and damping emulations in semi-active actuators are coupled quantities the control is formulated to prioritize the frequency control by the controlled stiffness. The control algorithm is augmented by a stiffness correction method ensuring precise frequency control when the desired control force is constrained by the semi-active restriction and residual force of the MR damper. The force tracking task is solved by a model-based feed forward with feedback correction. The MR-SVA is numerically and experimentally validated for the primary structure with nominal eigenfrequency and when de-tuning of −10%, −5%, +5% and +10% is present. Both validations demonstrate that the MR-SVA improves the vibration reduction in the primary structure by up to 55% compared to the passive tuned mass damper (TMD). Furthermore, it is shown that the MR-SVA with only 80% of tuned mass leads to approximately the same enhanced performance while the associated increased relative motion amplitude of the tuned mass is more than compensated be the reduced dimensions of the mass. Therefore, the MR-SVA is an appropriate solution for the mitigation of tall buildings where the pendulum mass can be up to several thousands of metric tonnes and space for the pendulum damper is limited.

Mitigation of chatter instabilities in milling using an active fixture with a novel control strategy

Chatter vibrations in machining have collected the interest of several research activities in the last decades, mainly due to its detrimental effect on productivity and surface quality. Several approaches and techniques have been developed to mitigate the effect of these unstable vibrations, but the required expertise and setup time usually prevent the widespread industrial application. Retrofittable intelligent active fixtures, capable of monitoring the process in real-time and exert adequate counter-excitations, could allow to overcome some of these limitations. Nevertheless, the use of these devices was always limited to the mitigation of structural chatter vibrations, which are the ones generally fitting in the device bandwidth. This paper deals with the development of an active fixture using an alternative control strategy that exploits low-frequency excitations, with the purpose of mitigating the chatter vibrations at frequencies exceeding the device bandwidth. The paper covers the main aspects of the fixture design and mainly focuses on the theoretical and practical aspects of the followed approach for the control. An experimental tests campaign is finally discussed to show that the proposed approach is actually effective in mitigating chatter vibrations.

Vibration Mitigation of Structures through TLCD with Embedded Baffles

In order to have an efficient Tuned Liquid Column Damper (TLCD) to mitigate vibrational energy of structures its damping level should be properly adjusted. This study proposes a new method of damping control of the TLCD by installing one-directional baffles. Compared to other existing methods, the proposed technique is simpler in design, easier in installation and maintenance, more practical to be used in real scale TLCDs, and has high potential to be used as an active control damping system. In this study, the dynamic characteristics of modified TLCD with different types of baffles were obtained by investigating their effect on the characteristics of Structure-TLCD system (S-TLCD), and structural responses of the S-TLCD under harmonic excitation. The effects of baffles were checked in three places with five different blockage ratios. TLCD equipped with baffles located horizontally at the external side of columns’ entrance, which is called Horizontal Side Baffle (HSB) with 60 % blockage ratio (T + HSB60) showed the best performance among different types of studied baffles; it increased the damping of the structure from 1.2 to 8 % and reduced the maximum acceleration response by 77 %. However, the TLCD without baffles increased the damping to 1.8 % and reduced the maximum acceleration response by 59 %. Installation of HSB60 increased the head loss coefficient of conventional TLCD 4.8 times, while it had an insignificant effect on natural frequency.

Optimal inverse magnetorheological damper modeling using shuffled frog-leaping algorithm–based adaptive neuro-fuzzy inference system approach

Magnetorheological dampers have become prominent semi-active control devices for vibration mitigation of structures which are subjected to severe loads. However, the damping force cannot be controlled directly due to the inherent nonlinear characteristics of the magnetorheological dampers. Therefore, for fully exploiting the capabilities of the magnetorheological dampers, one of the challenging aspects is to develop an accurate inverse model which can appropriately predict the input voltage to control the damping force. In this article, a hybrid modeling strategy combining shuffled frog-leaping algorithm and adaptive-network-based fuzzy inference system is proposed to model the inverse dynamic characteristics of the magnetorheological dampers for improving the modeling accuracy. The shuffled frog-leaping algorithm is employed to optimize the premise parameters of the adaptive-network-based fuzzy inference system while the consequent parameters are tuned by a least square estimation method, here known as shuffled frog-leaping algorithm-based adaptive-network-based fuzzy inference system approach. To evaluate the effectiveness of the proposed approach, the inverse modeling results based on the shuffled frog-leaping algorithm-based adaptive-network-based fuzzy inference system approach are compared with those based on the adaptive-network-based fuzzy inference system and genetic algorithm–based adaptive-network-based fuzzy inference system approaches. Analysis of variance test is carried out to statistically compare the performance of the proposed methods and the results demonstrate that the shuffled frog-leaping algorithm-based adaptive-network-based fuzzy inference system strategy outperforms the other two methods in terms of modeling (training) accuracy and checking accuracy.