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As the number of long-span bridges continues to grow, wind-induced vibration issues have become increasingly intensified. Among them, flutter is a serious wind-induced vibration that can lead to bridge collapse. To address this problem, this paper proposes inerter-based dampers as a solution for flutter control and compares their performance to traditional tuned mass dampers (TMDs). Firstly, eight distinct inerter-based dampers were proposed, based on various combinations of mass-inerter-spring-damper (MISD) components. Secondly, the equations of motion of the bridge-MISD system were derived based on the two-mode coupled flutter theory and the mechanical impedance analysis method. Thirdly, the flutter control performance of the eight proposed MISDs is examined using a simply supported beam, with the six better-performing dampers further evaluated using the Jiangyin Bridge. The results show that inerter-based dampers can effectively improve the critical flutter wind speed of bridges, with performance sensitive to frequency. Additionally, incorporating an inerter decreases the static displacement of the mass block, while increasing the mass of MISD and the distance between the damper and the section center improves flutter control performance. The optimal spring stiffness ratios for the six MISDs are identified, largely dependent on the damper's inertance and mass. In conclusion, this paper offers a promising solution to addressing flutter in long-span bridges and provides insights into the design and optimization of inerter-based dampers. [ABSTRACT FROM AUTHOR]

Pendulum tuned mass dampers (PTMDs) are one of the most commonly used devices for high-rise structures to control large-amplitude vibrations due to dynamic excitations. In practice, the damper of PTMD usually connects the tuned mass to the location below the top floor rather than to the top floor, which is different from the case using a conventional tuned mass damper (TMD). Therefore, the classical optimal parametric formulas derived from the structure-conventional TMD model are not applicable to design the optimal parameters of PTMDs. In this paper, the simplified mechanical model of the structure-PTMD system is updated to consider the damper connection in practice. The fixed-points theory is employed to analytically derive the optimum design formulas for the PTMD by introducing the effect of modal shape. Moreover, the control effectiveness of the PTMD using the proposed method is studied. The control performance and robustness of the PTMD designed by the proposed method are compared to those designed by the classical optimum formulas under various dynamic loads. Finally, with the help of the performance degradation index (PDI), the control performance degradation of PTMD designed by classical formulas is quantified. The results show that the proposed optimal parameters have considerable differences from classical formulas. Through designing a PTMD on a multi-degree-of-freedom (MDOF) structure, the proposed optimum design is demonstrated to be more effective and robust than the classical formulas. To design a large mass ratio PTMD, the control performance degradation from the damper connection in practice is significant and should be seriously considered. [ABSTRACT FROM AUTHOR]

Recently, enhancing conventional tuned mass dampers (TMDs) with a pounding damping mechanism is demonstrated to be an efficient way for vibration control of flexible structures. In this paper, a double-tuned pendulum mass damper employing a pounding damping mechanism (DTPMD-PD) is proposed. DTPMD-PD dissipates energy through the collision between distributed balls with a smaller mass and viscoelastic (VE) boundary, which can effectively reduce noise during operation compared to conventional impact dampers. Moreover, DTPMD-PD utilizes a double-tuning mechanism, and its control performance is significantly enhanced. The motion equations of a multiple degree of freedom (MDOF) structure equipped with DTPMD-PD are formulated. Based on the H∞ optimization criterion, a numerical optimization is performed to obtain the optimal design parameters of DTPMD-PD. Additionally, the pounding dissipation capacity and the parametric identification of the impact force model are investigated through free pounding experiments, and the control performance and robustness of DTPMD-PD are experimentally studied in the laboratory. The results show that the proposed numerical modeling method has considerable accuracy through experimental verifications. The restitution coefficient of the pounding layer has a significant influence on the performance of proposed DTPMD-PD. Optimized DTPMD-PD has better effectiveness than conventional TMDs under harmonic and seismic loads. [ABSTRACT FROM AUTHOR]

Floating offshore wind turbines (FOWTs) are generally located in the harsh deep-sea environment and are highly susceptible to extreme loads. In order to ensure the normal operation of FOWTs, this article takes the semi-submersible FOWT as an example, proposes a new double-rope mooring system, and studies the dynamic performance of the FOWT with the double-rope mooring system and its effectiveness in reducing the dynamic response of the wind turbine. At the same time, the tuned mass damper (TMD) is installed in the nacelle of the wind turbine, and the TMD parameters are optimized considering the space limitation of the nacelle by limiting the TMD's stroke, which further reduces the dynamic response of the FOWT and improves its stability. Numerical simulation and analytical studies show that the new double-rope mooring system can reduce the dynamic response of the wind turbine to a greater extent than the traditional single-rope mooring system. Considering the stroke restriction, the control performance of TMD will be slightly weakened, but it is more in line with the actual engineering requirements. Compared with the original FOWT, the proposed new type of FOWT has better dynamic stability and has the prospect of extending to real engineering applications. [ABSTRACT FROM AUTHOR]

Modal properties of the primary structure and tuned mass dampers are basic parameters for in situ tuned mass damper frequency tuning and periodic condition assessment of the structure–tuned mass damper system. In this study, a state space technique is developed for identifying the respective modal properties of structure and tuned mass damper device from the dynamic responses of the coupled structure–tuned mass damper systems. The coupled structure–tuned mass damper system is represented by a reduced two-degree-of-freedom model which characterizes the coupled dynamics of the structural mode under control and tuned mass damper. A simple expression is derived for calculating the respective modal properties of the structural mode and tuned mass damper from the modal properties of the coupled two-degree-of-freedom model. Stochastic subspace identification is employed to estimate the modal properties of the combined system from ambient or free vibration responses. Numerical simulation of two structures and experimental validation of a laboratory steel frame equipped with a tuned mass damper are carried out to verify the proposed method. It is shown the proposed method successfully identifies the modal properties of both the structural mode under control and the tuned mass damper. Compared to the ambient vibration data, the identification results are superior when using the free decay responses. When the tuned mass damper is not perfectly tuned to the primary structure, much accurate identification results can be obtained, especially for the damping ratios of the primary structure and the tuned mass damper. [ABSTRACT FROM AUTHOR]

Owing to its easy implementation and robustness, the pounding tuned mass damper (PTMD), which uses viscoelastic materials to cover the pounding boundary to increase the energy dissipation during impact, has been studied in recent years. The conventional PTMD design includes a gap between the pounding mass and the viscoelastic material; the value of this gap should be optimized. In this paper, a novel PTMD is proposed to control structural vibrations. In the proposed PTMD, the pounding boundary covered by viscoelastic materials is simply added to one side of the tuned mass when the tuned mass is in the equilibrium position. Unlike the conventional PTMD, the gap between the tuned mass and the pounding boundary is zero in the proposed design and is no longer a design parameter. A new analytic model is proposed to accurately predict the impact force between viscoelastic materials and steel. Through comparison with the impact force and the indentation from impact experiments, the accuracy of the proposed impact force model is validated. To verify the control performance of the proposed PTMD, an experimental study on a frame with the proposed PTMD is carried out to investigate the control performance in free vibration and forced vibration cases. Both experimental and numerical results show that the proposed PTMD can effectively reduce the response of the frame structure and that the damping ratio of the frame is significantly increased. [ABSTRACT FROM AUTHOR]

Summary: This paper investigates the optimal design of the tuned viscous mass damper (TVMD) with linear and nonlinear viscous damping properties for a single degree‐of‐freedom structure subjected to harmonic excitation. The TVMD consists of a parallel‐connected inerter and viscous damper, and a spring that mounts them to the structure. To examine the vibration control performance of the TVMD, both theoretical analysis and numerical optimization are conducted to obtain the optimal parameters of the TVMD with either linear or nonlinear viscous damping. The influence of the damping exponent of the nonlinear viscous damper on the optimal parameters and performance of the TVMD is analyzed. The results show that much better control effectiveness and robustness can be achieved by the TVMD when compared with tuned mass damper (TMD). Furthermore, it is also of great practical importance to show that the static deformation of the supporting spring due to the self‐weight of the inerter is only a small fraction of the traditional TMD in case of vertical vibration control. Compared with the linear TVMD, the nonlinear TVMD can achieve comparable or even slightly better control performance. The optimal damping coefficient depends largely on the damping exponent, and the loading intensity fluctuation also has an influence on the performance of the nonlinear TVMD. Moreover, it is shown that that the nonlinear TVMD with damping exponent ν = 2 has the best control performance on the peak displacement response of the main structure, and the TVMD with linear viscous damping optimized for the harmonic excitation can also effectively suppress the wind‐induced vibration. [ABSTRACT FROM AUTHOR]

Summary: This paper proposes a new passive control device, pendulum‐pounding tuned mass damper (PPTMD), to mitigate the response of lightly damped structures under various excitations. The proposed PPTMD consists of a tuned pendulum mass and a pounding boundary next to the equilibrium position of the pendulum mass. Moreover, a layer of viscoelastic materials called high energy‐dissipation rubber is attached on the pounding boundary to dissipate the vibration energy through impacts. A simplified impact force model was developed for modeling the pounding behavior of the high energy‐dissipation rubber pounding layer, and parameters in the simplified model were identified from free pounding experiments. The validation of the numerical method to simulate the dynamic behavior of the PPTMD was provided. The effectiveness of the PPTMD to control a single degree‐of‐freedom structure was numerically and experimentally studied under free vibration and forced vibration. The effects of the frequency tuning ratio, the coefficient of restitution, the excitation force amplitude, and the mass ratio were studied, respectively. Finally, the control performance of the PPTMD was compared with the classic tuned mass damper under free vibration, forced vibration, and several earthquake records. It is shown that the PPTMD can significantly increase the damping ratio of the controlled structure and effectively reduce the response of the controlled structure around the resonant frequency range. Furthermore, the PPTMD still achieves considerable control performance even if the frequency of the controlled structure varied in a wide range. Due to the different vibration control mechanism, the PPTMD outperforms the classic resonant frequency range in controlling the structural displacement response. [ABSTRACT FROM AUTHOR]

This paper proposes a new method to mitigate vortex-induced vibrations (VIVs) of a bridge deck using a single-side pounding tuned mass damper (SS-PTMD). The SS-PTMD is a passive control device and comprises an undamped tuned mass with a pounding boundary covered with viscoelastic (VE) materials layer. A nonlinear force model for describing impact behavior of VE materials is used to simulate the response of a single degree of freedom (SDOF) system controlled by a SS-PTMD. The free pounding experiments are performed to determine the model parameters of impact force and validate the simulation method. The optimal design of SS-PTMD for SDOF system subjected to sinusoidal excitation is carried out by numerical optimization, and the optimized SS-PTMD is applied to control the vertical VIVs of a bridge deck. The control performance is experimentally examined by elastically mounted section model tests in wind tunnel. In addition, the classical wake oscillator model is used to predict the behavior of the coupled fluid-structure system under VIV and explore the control performance of the SS-PTMD. The experimental results show that the maximum response of the bridge deck model was reduced by 94% when a SS-PTMD with mass ratio of 2% was applied. It is also shown that nonlinearity in vortex shedding forces has little influence on control performance of SS-PTMD optimized under sinusoidal excitation. [ABSTRACT FROM AUTHOR]

Traditional tuned mass damper (TMD) devices requires heavier masses and additional dampers to improve their vibration control performance. In this paper, a novel tuned hydrodynamic mass damper (THMD) is proposed for vibration control employing added mass and damping from the interaction between heave plate and fluids. The added mass can reduce the weight of the mass block and improve the performance of conventional TMD devices. Moreover, the added damping can replace fluid or eddy current dampers in the traditional TMD system and result in lower costs. The equations of motion of the THMD-single-degree-of-freedom (SDOF) system is established with the help of the Morison equation. The corresponding semi-analytical solutions are obtained using the harmonic balance method, and the approximate analytical solutions of optimal parameters are also derived based on the H ∞ criterion. The control performance and robustness of THMD are compared with the conventional TMD and the heave plate cases by numerical analysis. Moreover, the parametric identification of the Morison equation is performed by a forced experiment in water and the accuracy is verified through Computational Fluid Dynamics(CFD) analysis. Finally, a controlled structure and a THMD are manufactured in the laboratory where the THMD is designed by the analytically optimal solutions. The results show that the semi-analytical solutions of motion equations derived by the harmonic balance method agree well with the numerical optimization solution, and analytical solutions of optimal parameters of THMD are highly accurate. The THMD outperforms the conventional TMD and heave plate under broadband harmonic loads according to the numerical and experimental analysis. the THMD outperforms the conventional TMD and heave plate under broadband harmonic loads. When the ratio of mass μ is set to 0.045, a THMD with a added mass ratio β of 0.031 has a 32.7% reduction in peak value of DMF compared to a conventional TMD. [ABSTRACT FROM AUTHOR]

Active vibration control is not only suitable but also urgently needed in order to mitigate excessive vibration for dynamic systems such as wind turbine towers. However, there is a challenge of directly observing displacement and developing an efficient reduced-order control strategy. With this in view, a reduced-order controller based on displacement observation is developed for the vibration mitigation of flexible high towers, where the problems of low signal-to-noise ratio (SNR) and intricate acceleration-based control algorithms are eliminated completely. The displacement can be measured by laser or modern videometrics technology. A reduced-order model with an active mass damper (AMD) at the top of the tower is created using modal truncation approach based on modal participation factor (MPF), which successfully preserves the dominant modes of the original structure, and reduces the influence of high-frequency uncertainties. Considering structure uncertainties caused by environmental factors and aging process, an unscented Kalman filter (UKF) is introduced to identify the modal stiffness of the reduced-order model. The present study, using a 5 MW onshore wind turbine as an example, investigates active vibration control under wind and seismic loads and compares it with traditional tuned mass damper (TMD). From a dynamic perspective, the simplified model of wind turbine tower takes the form of a multi-degree-of-freedom series model. Consequently, a six-story steel frame platform has been constructed to experimentally validate the efficacy of the reduced-order controller. According to numerical simulation and laboratory testing, the control effect of the reduced-order controller with a few displacement states as feedback can be utilized as an active control strategy for high-rise flexible towers. • A displacement feedback controller is designed for active control of practical engineering of HAWT. • The work simplifies the complicated wind turbine active reduction problems into a reduced-order active control issue. • The latest achievement of displacement observation technology with videometrics was introduced. • This study provides a complete platform involving model development - algorithm simulation - experimental verification. [ABSTRACT FROM AUTHOR]

Extra long stay cables, owned characteristics of light weight and low damping, may produce large-amplitude vibrations in modes with relatively high frequencies under a moderate wind speed. Installing a transverse fluid viscous damper near the cable anchorage to add maximum damping to the first few cable modes is a traditional method to improve the cable modal damping ratio. However, the installation location of the damper may be coincide with the nodal point of some high vibration modes, and diminishing the damping effect to a large extent. To tackle this nodal mode issue, a single-sided pounding tuned mass damper (SS-PTMD), which exhibits superior control performance over a conventional tuned mass damper (TMD), is adopted to enhance the damping ratio of nodal modes. The coupled equations of motion of a cable equipped with a SS-PTMD are established, and impact force between damper mass and the cable are considered by a impact force model. Free pounding tests are performed to study the pounding behavior with different viscoelastic (VE) material layers and various types of pounding strikers. Numerical simulations are carried out to investigate the damping enhancement and vibration mitigation effect of the SS-PTMD on the cable under various loading cases, including harmonic and simulated turbulent wind excitations. Field performance validations of the SS-PTMD is performed on a cable numbered A10 of the Dongting Lake Bridge. The results from free pounding tests show that the selection of the VE material layers and strikers can greatly affect the pounding behavior of the SS-PTMD. The Numerical simulation of the coupled cable-SS-PTMD system reveals that the SS-PTMD can effectively enhance the damping ratio of the target mode by a SS-PTMD with only 1.08% mass ratio. The numerical results show that SS-PTMD is effective in mitigating the high-oder nodal mode vibration of the cable. Field tests show that after the installation of SS-PTMD, the 2nd-mode modal damping ratio of the cable increases from 0.15% to 1.8%. • SS-PTMD is proposed to enhance the damping of stagnation modes for stay cables. • The pounding behavior with different material layers and strikers is investigated. • The damping enhancement and vibration mitigation effect of SS-PTMD are studied. • Field tests are carried out to validate the damping effects of SS-PTMD. [ABSTRACT FROM AUTHOR]

In recent years, the criticality of fore-aft vibrations induced by winds on wind turbine towers has increased; these vibrations are generally evaluated using equivalent fatigue load (EFL). This is the first study to adopt wind speed histories from large eddy simulations as input for dynamic analysis of wind turbines, and to evaluate EFL against real wind distribution. Tuned mass damper (TMD) and rotational inertial double tuned mass damper (RIDTMD) were employed to control these vibrations. Parametric analysis of the damper parameters was conducted. An innovative global optimization tool was developed based on a radial basis function neural network and genetic algorithm. Moreover, for the first time, GPU acceleration technologies were adopted to enable the optimizations of dampers through massive cases. Numerical results show that damper optimizations under real wind distributions are essential, and that optimized dampers reduce 44% EFL. The performance of RIDTMD is better than TMD but has a narrower system control bandwidth. The optimized dampers are significantly affected by wind speed; however, they are least affected by wind direction. The developed GPU-based codes can run 2001 times faster than the CPU-based ones, and the optimization tool can further reduce 85% computational time, which is open to other researchers. • TMD and RIDTMD are employed to control fore-aft vibration of wind turbine tower. • Novel GPU-accelerated codes are developed for dynamic response analysis and are 2000 times faster than CPU-based ones. • Newly developed RBFNN-GA-based tool is utilized to globally optimize dampers and reduces 85% computational time. • For the first time TMD and RIDTMD are optimized against real wind distribution and obtain about 44% EFL reductions. • For TMD, μ = 0.21 and v = 1.05; for RIDTMD, μ = 0.21, ξ = 0.42, and v 2 = 1.6 are recommended for the wind turbine. [ABSTRACT FROM AUTHOR]

• Evaluation of PPTMD for seismic control of structures is carried out by shake table tests. • The optimal design of PPTMD is implemented. • The control performance of PPTMD is compared to that of TMD. The pendulum pounding tuned mass damper (PPTMD) is an effective passive control device for structures under harmonic excitations. The primary objective of this study is to evaluate the performance of PPTMD for vibration control of SDOF and MDOF structures subjected to ground motions. The dynamic equations of motion for a primary structure controlled by a PPTMD are formulated and the parameter of the PPTMD was obtained through minimizing the root mean square (RMS) of the free vibration response of the controlled structure. The control performance of PPTMD with the optimized parameters was verified by shake table tests of a SDOF structure under three different earthquakes. The effect of the mass ratio and frequency detuning of the PPTMD on its control performance under 17 different earthquake records with different frequency components was further investigated, and the comparison with the classic tuned mass damper (TMD) was also conducted. Additionally, the influence of the inherent damping ratio of primary structure and earthquake intensity to the control performance was discussed. It is shown that the proposed optimum parametric formulas can be used for the optimal PPTMD design, and both numerical and experimental results demonstrated that the PPTMD effectively suppressed the structural responses, even under detuning situations. The inherent damping of primary structure decreases the control efficiency of PPTMD. Moreover, the control performance of the PPTMD on 10-storey shear structure was studied. As a single-mode controller, the PPTMD is more effective when the structural vibration of target mode is mainly excited under seismic excitations. [ABSTRACT FROM AUTHOR]

Excessive fore-aft vibrations of wind turbine tower are the major reason for tower collapsing, which can be evaluated using the equivalent fatigue load (EFL). Wake effects are generated by the former wind turbines on the latter ones, and can greatly increase EFL and reduce lifetime of the latter ones, but they were seldom considered. Consequently, this study calculated EFL countering the wake effects under real wind distributions. The effects of wind turbine spacing on EFL indicate that the wake effects between wind turbines with spacing of approximately 2 times of rotor radius should be considered. Subsequently, tuned mass damper (TMD) was placed in the nacelle to passively control the fore-aft vibrations. An optimization tool for TMDs was developed based on the radial basis function neural network and genetic algorithm, which was compared with the theoretical equations and parametric analysis. GPU acceleration technology was utilized. Numerical results show that, under real wind distributions, the TMDs obtain at least 40.1% EFL reduction, which is 8.9% higher than the theoretically optimized one. Importantly, the GPU-based codes can run 2001 times faster than the CPU-based ones, and the optimization tool can reduce 44.9% computational time further. The codes are made available for other researchers. • PyGAOWT is validated against commonly used GH-bladed and obtains well agreements. • GPU-accelerated PyGAOWT can run 2001 times faster than CPU version and is opened. • RBFNN-GA-based optimization tool performs better and reduces 45% time compared with parametric analysis. • For wind turbines with spacing of about 2 times of rotor radius, TMDs should be applied. • TMD is optimized under real wind distribution instead of white noise with wake effects countered. [ABSTRACT FROM AUTHOR]

A peculiar wind-induced vibration with large acceleration amplitude, super-high and narrow frequency bands was observed on ultra-long stay cables after one-year-more field monitoring on the Sutong Bridge. The vibration was found extremely detrimental and cannot be suppressed by a single damper system. Based on this, it is first demonstrated that the vibration is a unique vortex-induced vibration resulting from the damper installation position, and which is named stagnation point-induced vibration (SPIV). Subsequently, a Stockbridge damper (SBD) scheme, usually used on transmission lines, is introduced to suppress the SPIV: the dynamic model of the stay cable-SBD system is established; the additional damping ratios are calculated based on the proposed model and the equations; moreover, parameter optimisation analyses of the SBD are conducted. Then, a real SBD is designed, produced, and finally installed on an actual stay cable with a length of 551 m based on the optimum parameters. Finally, with six months of field vibration monitoring data, the proposed dynamic model and the SBD damping scheme are demonstrated effective to the suppression of the detected SPIV. The study is expected to give a practical vibration control reference for ultra-long stay cables that are more than 500 m. • A peculiar wind-induced high-mode vibration on stay cables were observed through long-term field monitoring. • The vibration is proved being related to the installation position of the existing dampers. • A novel Stockbridge damper scheme was introduced to suppress the vibration. • A practical Stockbridge damper is fabricated and installed on an actual stay cable with a length of 551 m. • The practical vibration suppression effects of the proposed damper system were proved through long-term field monitoring. [ABSTRACT FROM AUTHOR]