Vibration Mitigation Of Structures Research Articles

Damage-aware structural control based on reinforcement learning

This contribution presents a semi-active control technique intended for mitigation of structural vibrations. The control law is derived in a repeated trial-and-error interaction between the control agent and a simulated environment. The experience-based training approach is used which is the defining feature of the machine learning techniques of reinforcement learning (RL). In particular, a specific modification of the Deep Q Learning (DQN) approach is applied. The involved artificial neural network not only approximates the expected reward of the control (which defines the control action and quantifies its performance), but additionally keeps track of structural damages. This requires a specific architecture, which allows the network to be damage-aware, and a specific training procedure, where the memory pool preserved for the RL stage of experience replay is populated with not only the observations, control actions, and rewards, but also with the momentary status of structural damage. Such an approach explicitly promotes the damage-awareness of the control agent. The proposed technique is tested and verified in a numerical example of a shear-type building model subjected to a seismic excitation. A tuned mass damper (TMD) with a controllable level of viscous damping is used to implement the semi-active actuation, and the optimally tuned classical TMD provides the reference response.

Analysis of Pedestrian Steel Bridge Subjected the Seismic Load And Wind Load Using Damper at Different Span

A Pedestrian steel truss bridge model was created by using structural analysis by software. With the similar loading and support condition the 3D model was analyzed for different span like 20m, 25m,30m the basic emphasis has been given decreases the response of structure member by providing damper at different span I section Girder, steel plate thickness. Steel girder and M40 grade of concrete is used for column section in Etab software. The dynamic loading caused by moving pedestrian and earthquake and wind load, Excessive vibration in footbridges usually occurs when they are subjected to rhythmic dynamic loads caused by human activities like walking and running. In order to mitigate the human induced vibrations in footbridges, an increase in the damping ratio is often suggested as the most economical approach. Tuned mass dampers have been widely used for this purpose, however, their installation and maintenance costs are high. This has encouraged researchers to examine the efficiency of the other types of dampers. Viscoelastic dampers have been successfully employed for vibration mitigation of structures against wind and earthquake loads.

Experimental design and adaptive modulation of piezoelectric cantilever phononic crystals for vibration attenuation in vehicle subframes

To attenuate the vibrations in the vehicle subframe with changing target frequency, a piezoelectric cantilever phononic crystal (PC) and its adaptive modulation strategy are investigated in this paper. First, based on the cantilever-based PC structure, the bandgap characteristics are obtained by vibration transfer calculation and piezoelectric constitutive modeling. The experimental design of the piezoelectric cantilever PC is further conducted based on the parametric analysis results of structural dimensions and the targeted vibration frequency intervals required by the vehicle subframe. The modal experiments indicate that two local resonant bandgaps and one electromagnetic oscillation bandgap appear in the solved frequency interval, and both of them exhibit excellent consistency with the theoretical calculations. Finally, an adaptive bandgap modulation strategy is proposed by controlling the shunting circuit parameters, and the execution results demonstrate that the PCs employed in the vehicle subframe can effectively achieve vibration attenuation from the powertrain systems. Starting from the experimental design and adaptive modulation of cantilever PCs with piezoelectric materials, this research presents a novel framework for the application of acoustic metamaterials in the vibration mitigation of automotive structures.

A hybrid clustering-based type-2 adaptive neuro-fuzzy forecasting model for smart control systems

The practical applicability of smart control systems suffers from the existence of uncertainty in the physical parameters, sensor measurements and external excitations. Effective methods and its ease of implementation are required in the real-time active control strategies. To this end, in this research, we introduce an overlapping clusters and Multilayer Extreme Learning Machine (ML-ELM)-aided interval type-2 Takagi-Sugeno fuzzy inference system for vibration mitigation of smart structures. The combined Fuzzy C-Means (FCM) and imperialist competitive algorithm (ICA) with respect to degree of fuzzy overlap between clusters was utilized for characterizing the upper and lower membership functions forming the antecedent part. Furthermore, indeterminacy was modeled as footprint of uncertainty (FOU) and automatically formed based on statistical characteristics of soft clusters. The consequent parameters were adjusted by hybridization of ML-ELM and overlapping clusters, then the adaptivity was guaranteed. The predictive accuracy and generalization capability of the proposed method were demonstrated over the estimation of active control effort. Finally, to prove the practicability of the implemented framework, it was applied to four high-rise, mid-rise and low-rise benchmark building structures equipped with active mass damper (AMD), active tendon and active bracing system (ABS). The obtained results demonstrated the higher predictive accuracy and generalization ability of the presented data-driven control scheme compared to the other standard technical machine learning strategies. This practical guideline is easy to implement and automates control engineering tasks in real-time applications, solving one of the most challenging aspects of smart control systems.

Optimization of tuned mass dampers for multiple mode vortex-induced vibration mitigation in flexible structures: An application to multi-span continuous bridge

Tuned mass dampers (TMDs) have proven effective in suppressing structural vibration. In existing research on vortex-induced vibration (VIV) control of flexible structures, only one mode is commonly considered at the time, and only basic aerodynamic force models, which can struggle to model amplitude-dependent damping, are considered. However, flexible structures, such as multi-span bridges, exhibit multiple modes with closely spaced frequencies. Neglecting secondary modes may introduce calculation inaccuracies, as these modes can impose additional stiffness, thereby influencing the performance of TMD. This paper presents a framework to optimize the performance of multiple TMDs in the context of multi-mode VIV control for a flexible structure. A multi-span bridge is used as a case study, and the secondary modes and nonlinear aerodynamic effects are considered. The governing equations for the force-structure-MTMDs system are derived in modal coordinates using a polynomial model to model the aerodynamic force. A novel method to calculate the contribution of each mode to determine the minimum number of secondary modes to be considered is proposed. The optimal parameters of MTMDs are obtained using a global optimization method and compared with mode-by-mode design results. Robustness analysis is conducted to verify the effectiveness of the optimization framework. The results show that the polynomial model accurately predicts the amplitude after TMD installation. Secondary modes significantly affect the optimal parameters of TMDs, and the optimized results exhibit better control performance than the mode-by-mode design results.

Structural vibration mitigation via an inertial amplification mechanism based absorber

This paper proposes a novel passive vibration control system, namely the Inertial Amplification Mechanism-based Absorber (IAM-A), to mitigate unwanted structural vibrations. With the help of the H2 and H∞ optimization methods, closed-form formulas for the design parameters of the proposed IAM-A are obtained. Parametric studies are conducted to evaluate the influence of the design parameters on the vibration mitigation performance of the proposed IAM-A. Finally, numerical simulations are performed to validate the efficiency of the IAM-A. For comparison, time history analyses of a structure with IAM-A, with TMD, and without control under earthquake ground motions are performed. Numerical results confirm that dynamic responses of the primary structure are suppressed when the TMD is introduced. But, the relative displacement responses between the primary structure and the absorber are relatively large. The proposed IAM-A outperforms the TMD. With respect to those of the TMD, dynamic responses of the primary structure with the proposed IAM-A are further suppressed. More importantly, the large relative displacement response of the absorber is reduced by more than half.

Multiple-input multiple-output active vibration control of a composite sandwich beam by fractional order positive position feedback

Positive Position Feedback (PPF) is an active vibration control algorithm widely employed for the vibration mitigation of thin-walled structures equipped with active flexural patches. Fractional order PPF (FOPPF) is a recent development of PPF that has been shown to achieve substantially better spillover characteristics, thanks to the inclusion of fractional calculus. However, so far, FOPPF literature has focused almost exclusively on single-input–single-output (SISO) applications, with little consideration of multiple-input-multiple-output (MIMO) capabilities and no experimental work on the subject. To fill this gap, a MIMO FOPPF control architecture was tested numerically and experimentally on a cantilever composite sandwich beam of rectangular section. The feedback algorithm involved two piezoelectric actuators and two piezoelectric sensors in a collocated configuration for the control of the lowest four resonances of the beam, excited by a random external excitation. The participation matrices, necessary for the simulation of the response of the electromechanical system, were obtained with a recently developed experimental method. The fractional orders of derivation, together with other controller parameters such as gain, resonant frequency and damping ratio, were chosen according to an optimization algorithm aimed at the vibration amplitude reduction of the first four resonances of the controlled system. As a result, the performance of the vibration control resulted superior to the equivalent PPF with integer exponents, both in simulations and experiments.

Evolutionary Computation-Based Active Mass Damper Implementation for Vibration Mitigation in Slender Structures Using a Low-Cost Processor

This work is devoted to design, implement and validate an active mass damper (AMD) for vibration mitigation in slender structures. The control law, defined by means of genetic algorithm optimization, is deployed on a low-cost processor (NI myRIO-1900), and experimentally validated on a 13.5-m lively timber footbridge. As is known, problems arising from human-induced vibrations in slender, lightweight and low-damped structures usually require the installation of mechanical devices, such as an AMD, in order to be mitigated. This kind of device tends to reduce the movement of the structure, which can be potentially large when it is subjected to dynamic loads whose main components match its natural frequencies. In those conditions, the AMD is sought to improve the comfort and fulfil the serviceability conditions for the pedestrian use according to some design guides. After the dynamic identification of the actuator, the procedure consisted of the experimental characterization and identification of the modal properties of the structure (natural frequencies and damping ratios). Once the equivalent state space system of the structure is obtained, the design of the control law is developed, based on state feedback, which was deployed in the low-cost controller. Finally, experimental adjustments (filters, gains, etc.) were implemented and the validation test was carried out. The system performance has been evaluated using different metrics, both in the frequency and time domain, and under different loads scenarios, including pedestrian transits to demonstrate the feasibility, robustness and good performance of the proposed system. The strengths of the presented work reside in: (1) the use of genetic evolutionary algorithms to optimize both the state estimator gain and the feedback gain that commands the actuator, whose performance is further tested and analyzed using different fitness functions related to both time and frequency domains and (2) the implementation of the active control system in a low-cost processor, which represents a significant advantage when it comes to implement this system in a real structure.

Viscoelastic damper for vibration mitigation of footbridges

Footbridges are among long-span light-weight structures that because of their low damping ratio are susceptible to vibration. Excessive vibration in footbridges usually occurs when they are subjected to rhythmic dynamic loads caused by human activities like walking and running. In order to mitigate the human induced vibrations in footbridges, an increase in the damping ratio is often suggested as the most economical approach. Tuned mass dampers have been widely used for this purpose, however, their installation and maintenance costs are high. This has encouraged researchers to examine the efficiency of the other types of dampers. Viscoelastic dampers have been successfully employed for vibration mitigation of structures against wind and earthquake loads. However, their efficiency for reducing human induced vibration in footbridges has not been addressed. In this study, a real footbridge with a free span of 22.5 m and a width of 2.3 m was selected for numerical investigations. SAP2000 program was used to establish the finite element (FE) model of the footbridge. The established FE model was validated by comparing its natural frequencies with those measured on the field. FE model results indicated that the acceleration response of the footbridge exceeded the code specified limit. Therefore, a viscoelastic damper was designed and installed under the footbridge in order to reduce the acceleration response below the allowable level. Installation of the viscoelastic damper significantly decreased the vibrations. It was concluded that viscoelastic dampers were an economical and efficient solution for vibration problems in footbridges.

Viscoelastic damping design – A novel approach for shape optimization of Constrained Layer Damping treatments at different ambient temperatures

Passive damping plays an important role in the vibration mitigation of aeronautic structures. In contrast to active systems, passive damping systems do not require any energy supply. Thus, their readiness is independent, which reduces the failure probability compared to active systems. Constrained Layer Damping (CLD) has become an established treatment for damping bending vibrations. Unlike other passive systems such as shock-mounts, CLD can be compactly integrated into an existing structure as an add-on solution. However, the design scope is limited by mass constraints and the optimal design for maximum damping must be found by optimization. For this purpose, a novel optimization approach is presented. The layer widths of the core and face layers of a CLD structure are treated as design parameters. Compared to the strategy of placing CLD patches on vibration antinodes, the proposed approach provides up to 52 % higher damping. The optimal design of a generic beam structure is determined considering different modes, viscoelastic material stiffnesses and ambient temperatures. Furthermore, the simulated damping is experimentally verified for a shape-optimized beam. The analyses show that the optimal design depends significantly on the viscoelastic material stiffness and is therefore temperature dependent. As a consequence, a generalized design guideline for CLD treatments cannot be derived.

Surface wave suppression in granular media using a partially embedded meta-barrier

Existing studies on meta-barrier designs for suppressing surface modes in inhomogeneous granular media are limited to meta-barriers comprising vertical or horizontal oscillators. However, a clear understanding of the surface mode hybridizations with the local resonances of the resonators is lacking and could help realize more realistic meta-barrier designs for surface wave control in granular media. In this work, we propose a meta-barrier comprising partially embedded rod-like resonators to study the hybridization of the fundamental surface modes: PSV1 and PSV2, with the longitudinal and flexural resonances of the resonators that enable surface mode suppression. The hybridized dispersion curves and frequency-domain finite element simulations with the meta-barrier demonstrate preferential hybridization of the PSV1 mode with the longitudinal resonance of the resonators, enabling PSV1 mode suppression above the hybridized longitudinal-resonance mode cut-off frequency. Unlike the PSV1 mode, PSV2 hybridizes with both longitudinal and flexural resonances, making it challenging to suppress the mode. However, we observe that enhancing the filling fraction of the meta-barrier promotes PSV2 mode suppression as the flexural-resonance hybridized modes are localized under the meta-barrier. The time-domain finite element simulation using a broadband excitation source further numerically validates the meta-barrier design for applications in vibration mitigation and seismic isolation of structures.

Mitigation of Structural Vibrations Due to Pulse-Type-Near-Fault Earthquake by the Compliant Liquid Column Damper

Pulse-type-near-fault (P-N) earthquake ground excitations can inflict serious damage to structures in built-up areas situated close to seismic faults. The high frequency content, high velocity pulses of long period, and fling effects cause P-N motions to impose large demands on both stiff and flexible structures. Among various passive control devices, the liquid column damper (LCD) is economical and its effectiveness is well-established for flexible structures under far-field earthquake ground motions. In this paper, the compliant form of the LCD (CLCD), which was specially developed to overcome the nonapplicability of the conventional LCD to stiff structures, is investigated for the vibration control of both stiff and flexible structures subjected to P-N ground motions. The study is carried out both in the frequency and in the time domain. Results indicate that the CLCD is successful in mitigating structural response to P-N ground motions. Some of the trends of response reduction with damper parameters are found to be different from those earlier reported for far-field earthquakes. Interestingly, in the case of flexible structures, while the CLCD is found to be fairly effective, the conventional LCD is rendered practically ineffective.

Analytical Research on the Mitigation of Structure-Borne Vibrations from Subways Using Locally Resonant Periodic Foundations

Filtering properties of locally resonant periodic foundations (LRPFs) have inspired an innovative direction towards the mitigation of structural vibrations. To mitigate the structure-borne vibrations from subways, this study proposes an LRPF equipped with a negative stiffness device connecting the resonator and primary structure. The proposed LRPF can exhibit a quasi-static band gap covering the ultra-low frequency range. These frequency components have the properties of strong diffraction and low attenuation and contribute the most to the incident wave fields impinging on nearby buildings. By formulating the interaction problem between the tunnel-ground and LRPF-superstructure systems, the mitigation performance of the proposed LRPF is evaluated considering the effects of soil compliance and superstructure. The performance depends on the dynamic properties of the ground, foundation, and superstructure as well as their coupling. Transmission analyses indicate that the superstructure responses can be effectively attenuated in the quasi-static band gap by adjusting the negative stiffness. Considering the coupling of the flexible ground, the peak responses of the LRPF-superstructure system occur not only at its eigenfrequencies but also at coupled resonance frequencies due to the contribution of the soil compliance. This study provides an analytical tool for mitigating the structure-borne vibrations from subways with the LRPF.

Development and design of a deep tank damper with submerged suspended plate

An appendage, in the form of a submerged suspended plate (SSP) in a liquid-containing deep tank, is proposed for converting functional liquid storage tanks into passive tank dampers for structural vibration mitigation. The oscillating frequency of the SSP is designed to be tuned to the structural frequency so that the tank damper is independent of detuning effects that could be caused by liquid level fluctuations. Further, the impulsive, rather than the sloshing, liquid mass is utilized here. This alleviates the disadvantage of low energy dissipation associated with the relatively smaller proportion of sloshing liquid mass of a deep tank. The theoretical model and working mechanism of the deep tank damper with submerged suspended plate (DTD-SSP) are developed and the expression for the tuning frequency derived. A time-domain formulation for the structure-DTD-SSP system is presented and the design and effectiveness of the DTD-SSP for an example structure under base excitation examined. Further, the performance sensitivity to tuning ratio and comparison with the traditional tuned mass damper (TMD) are presented. Results indicate that with the proposed design, liquid storage tanks installed for other functional requirements can be converted into DTD-SSPs that can achieve significant response reductions comparable with that of TMDs.

Spring-controlled modified tuned liquid column ball damper for vibration mitigation of structures

Passive-tuned mass and liquid dampers are a popular choice among structural vibration control systems for being reliable, economical, and easy to implement. Therefore, meticulous and rigorous efforts have been devoted by researchers to develop various configurations of these systems for the enhancement of vibration mitigation efficiency, architectural flexibility, and versatility of application. However, experimental validation of these configurations has always been a challenging task for researchers. In this paper, an experimental validation has been conducted for the fused versions of tuned mass and liquid column damper known as tuned liquid column ball spring sliding damper (TLCBSSD) and tuned liquid column ball spring rolling damper (TLCBSRD). In these modified versions the ball inside the horizontal section of the damper has been attached with a spring. A series of shake table tests have been performed on 4 story frame structure under harmonic and seismic excitations to evaluate the vibration control performance of proposed dampers. The damper was placed on the top story of each experimental setup. A detailed discussion and analysis have been done based on the RMS acceleration, displacement, and inter-story drift of each story subjected to harmonic and seismic loadings for all test cases. Both proposed systems reduced the RMS response of the structure at resonant and seismic excitations. The vibration response has been significantly reduced for both systems, compared to reference TLCBD, at harmonic loadings including frequencies 0.65 Hz, 1.17 Hz, 1.30 Hz, 1.43 Hz, and 1.95 Hz, especially at resonant loading. Moreover, a detailed comparison between the normalized frequency responses from experimental and numerical studies has been presented. Overall, the proposed fused versions of tuned mass and liquid column ball systems have outperformed the reference TLCBD.

Adaptive sliding-mode control for improved vibration mitigation in civil engineering structures

Abstract. Seismic vibration control using a magneto-rheological damper is a technique that interests several researchers around the world. This technique offers suitable structural building protection, ensuring human safety against earthquake excitation damages. The robustness of these devices depended in many cases on the designed law of control. Over the years, research focused on the development and modelling of various controllers to enhance the structural vibration elimination of buildings. The emphasis of this paper is on the evaluation of semi-active control robustness to reduce the displacements of a three-storey tested structure. The semi-active control device is a magneto-rheological fluid damper installed on the ground floor of the earthquake's excited structure and is controlled by an adaptive non-linear controller coupled to a clipped optimal algorithm to drive the current. The proposed controller is a sliding-mode controller reinforced by an adaptive technique to perform the control gain choice and overcome the chattering problem. The present law of adaptation is a switching conditional law between two laws offering the required gain depending on the system state. The numerical simulation results prove the effectiveness of the proposed semi-active control strategy in attenuating the displacements of the tested structure.

Mitigation of Structural Vibrations of MDOF Oscillators by Modal Coupling Due to Hysteretic Dampers

In civil engineering, structural elements characterized by hysteresis are often encountered, such as materials with limited elastic fields, microsliding friction and elastomeric absorbers. Hysteretic nonlinearities produce a wide variety of dynamical phenomena, such as significant modal coupling, bifurcations and superabundant modes. This paper investigates nonlinear modal interactions in the dynamic response of a two-degree-of-freedom system (2DOF) with hysteretic elements. These phenomena are notably important in internal resonance conditions, where modal interactions produce strong modifications in the response with possible beneficial effects. In specific conditions, the transfer of energy between the two modes leads to a notable reduction in the maximum response amplitude; the exploitation of this feature to achieve vibration mitigation of the forced response is the main goal of the paper. Two configurations are investigated: the hysteretic element at the top (vibration damper) and the hysteretic element at the base (isolator). In both cases, several internal resonance conditions occur since, by increasing the excitation intensity, the frequencies of the hysteretic system change, as well as their ratio. Qualitative similar results are obtained, characterized by a transfer of energy between the two modes. For both configurations, the usefulness of exploiting these nonlinear phenomena in vibration mitigation has been shown.

Experimental Dynamic Response of a Multi-Story Frame Structure Equipped with Non-Conventional TMD Implemented via Inter-Story Isolation

A shaking table experiment conducted on a multi-degrees-of-freedom frame structure equipped with a non-conventional tuned mass damper (TMD) is presented. The non-conventional TMD is characterized by a high mass ratio, without adding further structural masses, and is realized via inter-story isolation. The structure top story mass of a four-story steel frame structure is isolated and converted into tuned mass, connecting to the substructure with two high damping rubber bearings placed in series. Aspects related to the dynamic structural response as well as the seismic effectiveness assessment of a non-conventional TMD are addressed. Three structural configurations are tested: the reference four-story structure, the three-story intermediate structure, and the three-story structure equipped with a non-conventional TMD. The input motion conditions considered are: white noise, sine sweep, and natural earthquakes. Through experiments, structural identification is carried out and different dynamic behaviors emerge for the configurations tested. The nonlinear effects provoked on the structure by the adopted isolators are investigated, showing high dissipative capabilities in a wide range of amplitudes of the excitation. It is demonstrated that a non-conventional TMD is a smart control strategy useful for enhancing structural vibration mitigation.

Triboelectric nanogenerator metamaterials for joint structural vibration mitigation and self-powered structure monitoring

A metamaterial-inspired triboelectric nanogenerator (META-TENG) is proposed in this work to simultaneously realize vibration suppression and energy harvesting. The compact META-TENG can generate low frequency local resonant phenomenon and significantly reduce the incident vibration at the low-frequency band. A planar spring is created, which guarantees low-frequency resonance and a sufficient triboelectric contact surface within a small-scale device. The bandgap property of the proposed metamaterial is then calculated using the finite element method and corresponds well with the experimental measurement results. To fabricate the TENG, fluorinated ethylene propylene (FEP) film and Ecoflex are employed as the negative and positive triboelectric materials, respectively. It is found that the introduction of multi-walled carbon nanotubes (MWCNTs) into Ecoflex is favorable for enhancing the META-TENG’s output performance, increasing the output voltage by almost three times. The charge density of the TENG can reach up to 453.1μC/m2under 5 N sinuous excitation. The periodic META-TENG configuration also exhibits satisfying vibration suppression performance, where the vibration amplitude of an aluminum plate integrating four META-TENGs is minimized by up to 87 %. The harvested energy from the META-TENG array enables an accelerometer and Bluetooth module to work in wireless mode, making the whole system achieve self-powered vibration monitoring.

Numerical Simulation and Torsional Vibration Mitigation of Spatial Eccentric Structures with Multiple Magnetorheological Dampers

Eccentric structures will have torsional vibrations subjected to earthquakes, which can accelerate the damage of structures, and even become the main cause of building collapse. Semi-active control systems equipped with multiple magnetorheological (MR) dampers have been widely applied in structural vibration control. In this study, numerical models of spatial eccentric structures with multiple MR dampers were established, and time history analysis was conducted to mitigate torsional vibrations of eccentric structures. Firstly, a full-scale spatial eccentric structure model with both plan asymmetry and vertical irregularity was established in OpenSEES, and the accuracy of the structure model was verified by comparisons with model results from SAP2000. Then, the mathematical model of MR dampers was introduced to the structure model using the ‘Truss’ element and self-defined material in OpenSEES, and damping forces obtained from the MR damper model were compared with experimental data. Finally, modal analysis and nonlinear time history analysis of the eccentric structure model equipped with multiple MR dampers subjected to different seismic excitations were performed. Comparisons between the seismic responses of the uncontrolled structure and the structure with multiple MR dampers were carried out to demonstrate the effectiveness of the MR control system. Numerical results show that the control system with multiple MR dampers can significantly attenuate the torsional vibrations of eccentric structures, and thus possess significant engineering application prospects.