Passive Tuned Mass Damper Research Articles

Real-time hybrid testing validation of a stiffness-controllable mass damper for reducing vibrations in nonlinear structures

The design of passive tuned mass dampers (TMDs) and the evaluation of their vibration control performance typically rest on the assumption that the primary structure is a linear system. The optimized TMD is then tuned to the natural frequency of the primary structure, enabling the transfer of vibrational energy from the structure to the TMD and its absorption through the damping mechanism of the TMD, thereby reducing vibrations in the primary structure. However, if the structure exhibits nonlinear behavior during an earthquake, causing the natural frequency of the primary structure to vary, the passive TMD may experience a detuning effect, leading to significant degradation in its control performance. To address this challenge, this paper introduces a novel mass damper with controllable stiffness (MDCS) that dynamically adjusts its stiffness to adapt to changes in structural frequency due to nonlinear responses. This feature enables the MDCS to maintain optimal performance under nonlinear conditions. First, a mathematical model of a nonlinear structure with an MDCS was established, and a least input energy method (LIEM) control law suitable for nonlinear structures was developed to minimize the total energy of the nonlinear structure and the MDCS. This study verified the theoretical model and the LIEM control algorithm by conducting real-time hybrid testing (RTHT) using a physical lever-type MDCS mechanism in combination with a nonlinear numerical (substructure) model. The RTHT results demonstrated that the MDCS provides superior vibration reduction and reduced stroke in nonlinear structures compared to passive TMDs, marking a significant advancement in vibration control for seismic applications.

Vibrations Control of a SODF Structure Using TMD and MR Damper with Fuzzy Logic Algorithm Based on Velocity

In this study, the effects of using a passive tuned mass damper (TMD) with optimal parameters and a semi-active magnetorheological damper (MR damper) have been evaluated separately and simultaneously to control seismic vibrations of a linear single degree of freedom system, which was a simple "mass-spring-damper" model. OpenSEES software was used to model the single degree of freedom system and TMD, and MATLAB software was used to model MR damper. Fuzzy logic algorithm was used by MATLAB to determine the appropriate voltage for MR damper. By solving the dynamic equation of the damper, its force was calculated and this force was applied to the single degree of freedom system by OpenSEES. In the following, incremental dynamic analysis (IDA) has been performed using 7 earthquake records with maximum acceleration of 0.1g to1.0g with incremental step of 0.1g. Earthquakes are applied to four models without dampers, equipped with optimized TMD, equipped with MR damper, and equipped with both TMD and MR damper. The results showed that the simultaneous use of TMD and MR damper had the greatest effect on controlling the vibration of the system and reduced the maximum displacement by 22.36% and the maximum base shear by 21.85% compared to the case without dampers. Also, using only MR damper had a greater effect than using only TMD on reducing the seismic responses of the single degree of freedom system.

Evaluation of wind-induced response of high-rise structure with TMD system by real-time hybrid simulation test with motor-driven shaking table

Due to the difficulty in constructing the small-scaled model of tuned mass damper (TMD) system to meet the requirement of dynamic similarity law, it is hard to evaluate the vibration control effect of passive TMD system on the wind-induced response of high-rise structure by wind tunnel test. The Real-Time Hybrid Simulation (RTHS) test could provide a suitable solution to this problem by increasing the size of the scaled TMD model to overcome the limitation in dynamic similarity law. A RTHS test system with a linear electric motor-driven shaking table was developed by the interface with model interface toolkit in general real time system operating environment. Taking the Guangzhou New TV Tower with a passive TMD system as an example, the Finite Element (FE) model of Guangzhou New TV Tower was selected as the numerical substructure and TMD system was selected as the experimental substructure, the RTHS test was conducted at a sampling frequency of 250 Hz to estimate the wind-induced response of this high-rise structure with a TMD system in various dynamic wind loading cases. To reduce the time delay effect generated by the nonlinear interaction between motion control system and experimental substructure, the adaptive time series (ATS) compensator for time delay compensation was proposed in the RTHS test. The RTHS results were also compared with the numerical simulation results using the FE model of the investigated object. The RTHS test with additional ATS time delay compensator can obtain more accurate experimental results. The effectiveness of the proposed RTHS test system was testified to be powerful test system to evaluate the wind-induced response of high-rise structures with complex passive TMD system.

Optimized design of multiple tuned mass dampers for vibration control of offshore wind turbines

Offshore wind turbines (OWTs) are dynamically sensitive structures to low-frequency wind-wave loadings due to their low damping and high flexibility. This makes them vulnerable to unwanted vibrations in ocean environments. Therefore, there is a need to implement innovative vibration control devices to suppress undesired vibration and ensure their structural safety. A tuned mass damper (TMD) has been a promising solution to control excessive vibrations recently in OWTs due to higher efficiency and low installation cost. However, TMD performance in vibration mitigation of OWTs when placed at a nacelle is still challenging to investigate because the generator torque and pitch control may affect the dynamics of the overall system. In this paper, an optimal multiple TMD system is designed by placing TMDs at optimal locations along the tower, which are defined using the maximum amplitude of the displacements for the first three natural frequencies of the tower. In addition, extensive simulations are carried out with integrated OWT-TMD systems to find the optimal mass ratio values and quantity of the TMDs. The TMD system is also tuned for several scenarios, including operating, parked, and idling conditions under the combined wind-wave loadings. A numerical model of the 5 MW NREL OWT developed in OpenFAST is considered as the baseline in this study. The results show a root mean square (RMS) response reduction of 10.2% and 42% in fore-aft (FA) and side-side (SS) tower displacement with optimally designed multiple TMDs. Moreover, improved mitigation effects on tower base moment of RMS 43.6% and 20.8% are observed in orthogonal directions, respectively. The findings of this paper may have the potential for designing passive TMD systems for vibration reductions in OWT.

Vibration control of a monopile offshore wind turbines under recorded seismic waves

The dynamics and vibration control of offshore wind turbines (OWTs) under wind, wave, and earthquake loads is an important but understudied topic, especially for fully coupled seismic analysis considering pile foundation flexibility of OWTs. In this work, we study the effect of multiple passive tuned mass dampers (MTMD) on a monopile OWT by using the fully coupled seismic analysis method. A combined shutdown procedures and MTMD vibration control strategy is proposed for the OWT. First, a state-of-the-art aeroelastic tool, FAST, is extended with a seismic load calculation module, and the numerically modeled monopile OWT addresses the effect of pile-soil interaction (PSI) by establishing ElasPile module in the updated FAST. Then, the focus is placed on the normal operation and emergency shutdown status of OWTs under the combined earthquakes, wind and wave conditions, and structural and motion responses are analyzed under various combination conditions through time-domain simulations, the dynamic characteristics of the OWT during realistic seismic events are shown. Sequentially, based on the proposed MTMD, the vibration migitation effects are evident for the operation OWT and the OWT with shutdown strategies during the combined loading conditions. The reduction in the extreme responses can be as high as 10.53% and 55.02% for the bending moment at the mudline in different OWT conditions, respectively. Therefore, the combined shutdown procedures and MTMD vibration control strategy of OWT is an effective vibration reduction method. Additionally, it is found that PSI has a significant impact on the dynamic characteristics and vibration control effects of OWT structures under wind, wave, and earthquake loads, and the coupled spring boundary condition on the basis of developed ElasPile module is recommended for seismic control analysis of OWT using the combined shutdown procedures and MTMD vibration control strategy.

Design of an Overhead Water Tank as a Passive Tuned Damper Using an Innovative Support System Adaptive to Liquid Depth Fluctuation in the Tank

Difficulty in maintaining tuning due to water depth fluctuation makes overhead water tanks (OWTs) ineffective as tuned liquid or mass dampers. Recently, a semi-active damper involving OWT, that varies the stiffness of the tank-supporting columns with liquid depth variation to maintain the impulsive frequency of the tank constant at a value required for tuning, has been proposed. In this paper, the concept is extended to develop a passive tuned damper involving the OWT (PTD-OWT), which is more reliable, cost-effective, and has a simpler configuration than its semi-active counterpart but achieves the same objective as the latter. For the PTD-OWT, a novel mechanism involving a spring-supported platform, a rigid frame, and tank-supporting columns is developed. The working principle and mathematical model of the PTD-OWT are presented followed by an illustrative design example considering the host building undergoing base excitation. The results revealed that the PTD-OWT remains tuned and thereby performs consistently despite wide variations in water depth in the tank. Significant reductions have been achieved by the PTD-OWT in peak and root-mean-square displacement and acceleration responses of the structure for a variation in liquid depth between 100% full tank to empty tank condition, with the maximum fall in control achieved as only 6.8%. A comparison of PTD-OWT is made with the case when the tank is designed as a conventional passive tuned mass damper (TMD) without the provision for maintaining tuning. The conventional mass damper suffers significant performance degradation as liquid depth fluctuates in the tank.

Semi-Active Groundhook Control of Offshore Tension Leg Platforms Using Tuned Mass Damper With Optimized Parameters and Magneto-Rheological Damper Under Multiple Hazards

Abstract The purpose of the current study is to recommend an offshore tension leg platform (TLP) semi-active control system to lessen vibrations caused by various risks, such as the wind load and regular and irregular waves. State-of-the-art indicates that there has not been much study on semi-active management of offshore TLPs exposed to numerous hazards while taking into account system nonlinearities and employing a control method that is resilient to uncertainty. An augmented velocity–displacement-based groundhook (AVDB-GH) semi-active control scheme using magneto-rheological (MR) dampers, which is an improvement over the displacement-based groundhook (DB-GH) control algorithm, is proposed. The proposed controller uses a semi-active tuned mass damper (SATMD) consisting of a passive tuned mass damper (TMD) and two semi-active MR dampers as the control devices. Constrained nonlinear optimization is used to determine the SATMD's optimized parameters in order to produce the best control performance. A significant reduction in surge response of TLP is observed both in the time domain and the frequency domain. Compared to the SATMD using the usual DB-GH algorithm, the suggested control strategy more successfully decreases the key response variables—deck displacement, power spectral density, and acceleration. The effectiveness of the controller is better for regular waves than for irregular waves and wind forces. Because the performance of the controller is unaffected by changes in the mass and stiffness of the TLP, the controller can be regarded as robust.

A Multi Tuning-Frequency Passive/On-demand Active Pendulum Tuned Mass Damper

The use of tuned mass dampers (TMDs) in high-rise buildings, towers, and other tall structures for mitigating wind-induced vibration has resulted in significant improvements in serviceability of such structures. In applications where more than one mode of vibration with distinctly different natural frequencies are in need of damping, multiple passive TMDs each tuned to one of the natural frequencies are needed. In many such applications, the excessive cost, weight, and space requirement of multiple passive TMDs are not acceptable. This paper presents a novel passive pendulum tuned mass damper (PTMD) which on-demand can switch to an active PTMD. In its default passive state, the proposed device is tuned to the first mode of the structure and acts as a traditional passive PTMD. In its active state, while staying tuned to the first mode passively, the PTMD simultaneously tunes itself to multiple higher order modes adding tuned damping and providing a multi-directional vibration control.

Vibration control of offshore wind turbines with a novel energy-adaptive self-powered active mass damper

Slender and flexible offshore wind turbines (OWTs) are vulnerable to external dynamic excitations, and passive tuned mass dampers (TMDs) have been widely used to control excessive vibrations of OWTs under harsh marine environments (e.g., strong winds and irregular sea waves). However, TMDs are only effective in the vicinity of the controlled frequency, i.e., in a narrow frequency band. Compared to passive TMDs, active control methods are normally considered to possess better control performances but at the cost of a large amount of external energy input. To this end, the present study proposes a novel energy-adaptive self-powered active mass damper (SPAMD) to mitigate the responses of OWT towers. The proposed control device can harvest energies from OWTs and then use them as the power to drive an active mass damper for structural vibration control. Specifically, a representative OWT is selected as a prototype structure and its tower is modeled as a multi-degree-of-freedom system by simplifying the rotor-nacelle assembly as a lumped mass and moment of inertia. The dynamic characteristics (mainly natural frequency and mode shape) of the tower obtained by the developed model are validated against a finite element model. Subsequently, the system configuration and working mechanism of SPAMD are introduced and SPAMD is incorporated into the developed model to simultaneously harvest energy and mitigate the fore-aft responses of the tower under wind and sea wave loads. The control effectiveness of SPAMD is further compared to the traditional TMD. Results show that SPAMD has a superior effect over TMD in controlling OWT responses.

A Virtual Mechanical System control law for energy transfer towards a single actuation point in [formula omitted] DOF buildings

Mitigating vibrations in engineering structures is of key interest, as they can lead to failure and/or discomfort. However, in some cases it is not feasible to actuate all the structure’s degrees of freedom, which makes vibration mitigation difficult. In this work, we investigate the addition of a single one-degree-of-freedom virtual mechanical system (VMS), as an active controller, to attract and mitigate the energy from an impulse load on the structure. To challenge the controller, an actuation point is chosen furthest away from the impact location. As it is implemented virtually, the coupling between the structure and VMS can be chosen freely. It is found that a skew-symmetric coupling generates a gyroscopic force that enables control over the structure’s mode shapes. Using this, the controller is tuned to achieve a beating phenomenon that attracts the vibration energy to the actuation location. A nonlinear damper, based on the slope of the envelope of the virtual velocity state, avoids reflection of energy to the structure and dissipates this unwanted energy. Furthermore, the virtual damper’s robustness to timing errors is investigated: damping too soon means an incomplete energy transfer to the VMS, damping too late leads to return of energy to the building. The tuning strategy of the VMS is applied to a 4 DOF and 60 DOF building benchmark. For comparison, a tuned mass damper (TMD) and a nonlinear energy sink (NES) are tuned as well. The VMS succeeds in decreasing the settling time significantly in both cases, while the performance of the passive TMD and NES is rather limited for this specific configuration.

Integrated design and real-world application of a tuned mass damper (TMD) with displacement constraints for large offshore monopile wind turbines

Passive tuned mass dampers (TMDs) have been increasingly investigated for vibration control of wind turbines. However, TMD designs based on individual or a few operating conditions may result in insufficient consideration of the TMD's impact on wind turbines. For instance, the influence of end-stop collision forces on the main structural damage may be significantly underestimated, thereby affecting the overall lifecycle evaluation. In this study, focusing on large offshore fixed-bottom monopile wind turbines, we propose an integrated TMD design methodology taking the damper displacement constraints into full account. A comprehensive optimization of the passive omnidirectional pendulum-type TMD is conducted considering large number of operating conditions in the offshore environment. Next, a real-world application of the optimally designed TMD is performed for a 6450 kW monopile offshore wind on the Yellow Sea, China. We develop an on-site testing methodology and evaluation criteria for assessing the effectiveness of the TMD offshore. The results of resonance, emergency stop, operatingand reliability test conditions demonstrate the following: under the optimized TMD design taking into account all operating conditions, the TMD with a mass ratio of 1.56% can offer added damping in the fore-aft and side-side directions of the turbine, and provides the desired damping ratio of 1%; within a 4% frequency range around the design frequency, the TMD achieves effective vibration control; at rated power, the TMD achieves a reduction of more than 50% in the amplitude of the tower base side-side bending moment (Mx). The integrated TMD design with displacement constraints allows for the optimal TMD design across all operating conditions, thereby achieving superior overall vibration control and reduction in fatigue loads. The successful real-world application of the TMD based on integrated design methodology is of high value to the research community.

Investigation of optimum tuned mass damper parameter according to stroke capacity

During major earthquakes, civil structures may collapse due to vibration that has a frequency close to the frequency content of the structure. Because of this, control systems have also been proposed for building structures. These systems can be active ones that are controlled by electronic devices or passive ones that are tuned mechanical systems. Passive tuned mass dampers (TMDs) include mass, stiffness element and damping element and these are tuned around the frequency of the structure. For optimum tuning and the complex nature of the mathematics under random vibrations, metaheuristic algorithms are needed to be used. In the presented study, TMDs are optimized via Jaya algorithm. The control system was optimized for displacement minimization of the structure. Additionally, the stroke amount of the system was limited. The stroke capacity factor was investigated for wide limits between 0.5 and 4 for normalized stroke according to the maximum displacement of the structure. The investigation was done for a single degree of freedom structure for a general conclusion. It is observed that the stroke limit did not affect performance and optimum parameters after 2.75. The small values of the stroke limit have significantly different optimum period. <w:LsdException Locked

Active Vibration Control of Wind Turbine Using Virtual TMD Algorithm Based on Aerodynamic-Structure-Servo Coupling Model

In order to extract more wind energy, the wind turbine rotor becomes larger and the tower becomes taller. With more flexibility and smaller damping, wind turbine tower is prone to vibrate in winds. Meanwhile, the tower suffers the periodic loadings caused by the rotor rotation in the operational condition. The excessive vibrations could not only significantly affect the power generation but shorten the structural life due to the fatigue as well. It is challenging to reduce the vibration caused by the rotor rotation using the passive tuned mass damper (TMD) and traditional LQR controller due to the limited effective bandwidth. Therefore, an active tuned mass damper (ATMD) using a virtual TMD algorithm is proposed to mitigate the along-wind vibration of the tower under parked and operational conditions. The virtual TMD algorithm exhibits wide effective bandwidth and only requires the acceleration information on the top of the tower or the relative displacement of the active TMD. Firstly, the aerodynamic-structure-servo coupling (ASSC) model of the wind turbine is established which considers the interaction among the aerodynamic load, structure, and servo system. Secondly, the accuracy of the ASSC model is then verified using the onshore 5 MW wind turbine by the National Renewable Energy Laboratory (NREL). Thirdly, the ATMD feedback control force is designed by the virtual TMD algorithm. Finally, the reduction effect on the along-wind vibration by the proposed controller is evaluated at both of operational and parked conditions using the ASSC model. The TMD and LQR controller are utilized for comparison. The numerical results demonstrate that tuned mass damper (TMD) system with fixed parameters becomes detuned and may loses its effectiveness at different wind speeds. In contrast, active control can suppress the vibration of wind turbines at different wind speeds. Compared to the LQR controller, the proposed controller can enhance the reduction effect of wind turbine response with smaller stroke and control force at operational conditions.

Seismic Response Control of a Nonlinear Tall Building Under Mainshock–Aftershock Sequences Using Semi-Active Tuned Mass Damper

Under the excitation of strong mainshock (MS), the structure will enter the nonlinear stage, whose hysteretic characteristic can be well-simulated by the Bouc–Wen (BW) model. The accompanying aftershock (AS) may increase structural damage and cause the safety problem, therefore, the advanced structural control technology is worthy of being applied to nonlinear structure under MS–AS sequences. The tuned mass damper (TMD) is a popular vibrational absorber, however, it is sensitive to the frequency deviation and may lose its effect for nonlinear dynamic response control in this issue. To protect the nonlinear tall building under MS–AS sequences effectively, a semi-active TMD (STMD) is investigated in this study, which can vary its frequency and damping in real time simultaneously. It can adapt to structural nonlinear behavior in each time segment through varying its stiffness according to the wavelet transform (WT) based algorithm, and meanwhile, enhance the energy dissipation through switching its damping coefficient in real time. A 10-story nonlinear tall building is proposed as a case study and for comparison, a passive TMD (PTMD) is used. Nine MS–AS sequences are elected and nonlinear structural control performance of STMD is highlighted. Results show that STMD can control structural displacement responses and base shear effectively and performs better than PTMD in reducing the plastic development of the structure as well. Further, energy analysis is proposed and it is verified that STMD has an excellent effect in decreasing the structural input energy from MS–AS sequences and dissipating more energy than PTMD. Especially, it is found that a strong AS may cause a larger response to the nonlinear structure than MS, while the nonlinear control effect of STMD is still significant in that case.

Bi-directional semi-active tuned mass damper for torsional asymmetric structural seismic response control

Tuned mass damper (TMD) is a popular vibration absorber. To improve the seismic protection performance of a bi-directional passive TMD, a bi-directional semi-active TMD (BSTMD) with adaptive stiffness, variable mass and semi-active damping is proposed in this study. The BSTMD can adapt to structural X- and Y-directional instantaneous frequencies at the same time under bi-directional ground motions, which are identified through wavelet transform (WT), and the instantaneous angle of a diamond spring device is adjusted according to the instantaneous frequency ratio of two directions, which means that the stiffness ratio of two directions is retuned first. Then, the mass is retuned to match the exact instantaneous frequency. At last, the semi-active damping is realized according to an extended output signals-based control algorithm. A two-directional asymmetric torsional benchmark model is proposed as a case study. For comparison, two optimal passive TMDs implemented in X and Y directions separately and two unidirectional STMDs with variable stiffness and damping implemented in X and Y directions separately are investigated as well. Numerical results show that under bi-directional earthquake excitations in the benchmark problem, the two optimal passive TMDs have a good control effect. Two unidirectional STMDs have the best aseismic mitigation effect generally, in both lateral and torsional dynamic responses; while the BSTMD has a comparable control effect with less electromechanical devices, and can reduce the stroke of unidirectional STMD to a great degree. Though the BSTMD is aimed at X- and Y- directional dynamic responses, it can control torsional responses effectively as well, and when the eccentricity is enlarged to double, it remains effective for seismic mitigation.

Assessing seismic mitigation schemes of tuned mass dampers for monopile offshore wind turbine including pile–soil–structure interaction

The study of a monopile offshore wind turbine with the soil–structure interaction effect is most challenging in structural design under multiple hazards, i.e., the combined wind, sea wave, and earthquake excitations. Different arrangements of passive tuned mass dampers (TMDs) were used to mitigate the service and seismic loads affecting an offshore wind turbine (OWT) including the pile–soil–structure interaction (PSSI) effect. Different schemes of passive TMDs, placed at the top of the OWT tower or also at the center of gravity (CG) of the OWT tower or at the connection between the OWT tower and monopile, were tested. Various arrangements of TMDs including the proposed herein top radial TMDs arrangements have been investigated to determine their validity in resisting vibrations resulting from service and earthquake loads. The lateral displacements, shear forces and bending moments in both horizontal directions and the axial forces all over the OWT tower and monopile heights were recorded to compare the performance of each mitigation scheme of TMDs. The comparison results showed that the TMDs placement should be at the top of the OWT tower and the top radial 6 TMDs arrangement was found to be the most effective mitigation scheme for all straining actions in the tower and the monopile of the OWT subjected to service and earthquake loads.

Design of Optimal Passive Tuned Mass Damper with Static Output Feedback and Updating Iterative Procedure

In this study, the optimal design issue of a passive tuned mass damper (TMD) was transformed into the nonsparse control gain matrix optimization problem, and a general passive TMD optimization design method to minimize structural mean square responses or impulse response is therefore proposed. The proposed optimization procedure combines the static output feedback (also known as direct output feedback) algorithm and the updating iterative procedure. The proposed method can be applied to variant design scenario, whether the main structure is single-degree-of-freedom (SDOF) or multidegree-of-freedom (MDOF) structures, undamped or damped structures, subjected to wind disturbances or earthquake excitations. In addition, the proposed method is capable to consider the excitation shaping filter, so the design results are more suitable for practical application. The design procedure of the proposed method is presented, and all the required weighting matrices are introduced and derived in detail. Firstly, the SDOF structures are used as the main structure to demonstrate the correctness of the proposed method. The numerical simulation results verify that the obtained optimal design parameters of TMD were found identical to some cases which contain the analytic solution. The accuracy and feasibility of the proposed design method are confirmed. Finally, a passive TMD is optimally designed for a 5-story MDOF structure subjected to Kanai–Tajimi spectrum comparable earthquakes and a 60-story high-rise MDOF structure subjected to Davenport spectrum comparable wind loads for demonstration.

An improved passive tuned mass damper assisted by dual stiffness

A tuned mass damper (TMD) is one of the oldest and most commonly used passive control devices attached to structures to absorb lateral loads of energy from main systems. In the last decades, several novel tuned mass dampers have been designed to increase the performance of TMDs in decreasing the structural responses during excitation vibrations. Moreover, several formulations and numerical optimization methods have been developed to optimize the TMDs parameters. This paper proposes a novel passive tuned mass damper with dual stiffness (DSTMD). The DSTMD includes mass, primary and secondary springs, dashpot, and motion limiting chamber. The performance of DSTMDs depends on their properties such as mass, primary and secondary stiffness, damping coefficient, and the length of the motion limiting chamber. Thus, a metaheuristic optimization algorithm, called the Mouth Brooding Fish algorithm, was used to optimize the DSTMDs parameters. The effectiveness of the optimum DSTMD on two different linear ten-story structures under several earthquakes has been studied and compared with the effectiveness of classical optimum TMDs. According to the study, optimum DSTMDs generally show better effects for certain excitations, and as an average performance, they are superior compared to the classical optimum TMDs in reducing maximum displacement of the buildings. At last, structural yielding is considered, and the performance analysis on this structure shows that the DSTMD has a superior effect in reducing the maximum displacement and is among the best methods for the calculated absolute yielding amount.

Machine learning driven damper for response control in vehicle–bridge interaction systems

The implementation of machine learning for the real-time prediction of the suitable value of the damping ratio of a semi-active tuned mass damper (SA-TMD) is investigated to ensure enhanced vibration control in vehicle–bridge interaction (VBI) problems. The response assessment of the uncontrolled, tuned mass damper (TMD)-controlled, and SA-TMD-controlled bridge models is performed under the Japanese Shinkansen (SKS) train model. The energy-based predictive (EBP) control algorithm is implemented for the bridge fitted with the SA-TMD. The EBP algorithm-controlled SA-TMD results in more effective suppression of the bridge vibration as compared to the passive TMD. However, the effectiveness of the EBP algorithm reduces for more complex VBI systems because of the increased computational time delay. To circumvent the effect of the delay, a control strategy is proposed based on the weighted random forest (WRF) algorithm. The WRF algorithm is trained based on the data obtained from the EBP algorithm-controlled bridge and implemented to suppress the vehicle-induced vibration of the bridge using SA-TMD. The results demonstrate that the implementation of the newly proposed WRF algorithm-based control strategy nullifies the effects of the computational time delay. Furthermore, it is established that the WRF algorithm suppresses the bridge vibration more effectively than the EBP algorithm.

Experimental study on adaptive-passive tuned mass damper with variable stiffness for vertical human-induced vibration control

Serviceability problem and human-induced vibration control of slender footbridges are of increasing interest to structural engineers. Passive tuned mass dampers (TMDs) have a wide range of applications in human-induced vibration control. However, a passive TMD is sensitive to the frequency deviation and, as a result a mistuned TMD will lose its control effect. An adaptive TMD can solve the mistuning problem of a passive TMD. However, there is few adaptive TMDs with variable stiffness in this issue. To fill this gap, an adaptive-passive variable stiffness TMD (APVS-TMD) is proposed in this study. The stiffness and frequency of APVS-TMD can be retuned through changing the length of free end of cantilever beam, while the damping can be retuned by adjusting the air gap between the conductor plate and magnets. As for the target natural frequency to be adjusted, the first two modal frequencies of the TMD-structure coupled system are identified under ambient excitation first, and then, the decoupled structural natural frequency is obtained according to the developed method based on the undamped 2-degree of freedom (DOF) modal analysis. By means of numerical simulation, the identification strategy is verified using a SDOF lumped mass main structure and an ideal simply supported beam model. Then, the identification and stiffness retuning operations of the APVS-TMD are further verified through a footbridge model experiment. Here, control effects of the APVS-TMD to walking- and running-induced vibrations are highlighted and compared with those of a mistuned TMD. Experimental results show that the APVS-TMD can identify the decoupled structural natural frequency from the coupled system accurately, and control human-induced vibrations effectively.