Narrow Results

The response amplification technology, which enhances the efficiency of shock absorption apparatuses, has been widely applied in the field of shock absorption control for engineering structures. Researchers have proposed and verified through numerical analysis and experiments more structural forms of this technology as applicable. The functions are also more comprehensive, such as increased utilization rate of structural space and economy. The development of its theoretical foundation has progressed from constant solutions based on small deformations to solutions that reflect the time-varying characteristics of the amplification factor of the brace-damping system. Simultaneously, the influencing factors of the amplification factor have been analyzed in detail to provide better theoretical guidance for engineering practice. This paper provides a detailed discussion on the research overview of the response amplification technology and the influencing factors of the amplification factor. The conclusion introduces the significance of using this technology, comprehensively analyzes the deficiencies and limitations of existing response amplification technology, and points out the research and development direction, with the expectation of providing ideas for further development.

Human–Structure Interaction (HSI) can significantly influence the dynamic characteristics of pedestrian footbridges, particularly those distinguished by their lightness and slenderness. This study examines the performance of Tuned Mass Dampers (TMD) and Semi-Active Tuned Mass Dampers (STMD) on pedestrian footbridges when their modal parameters change due to the influence of HSI. For this purpose, a 30 m long simply-supported footbridge with linear mass values ranging from 200kg/m to 2000kg/m and a fundamental frequency varying from 1Hz to 5Hz has been considered. In addition, several pedestrian streams with different pedestrian densities have been used to assess the structural dynamic response. The analysis highlights that structural lightness and slenderness are critical factors in determining whether the incorporation of an HSI model is relevant to accurately predict the dynamic performance of the structure. The findings indicate that while TMDs can become ineffective due to shifts in natural frequencies caused by HSI, resulting in a degradation of vibration reduction from 70–75% to 40–45%, STMDs demonstrate a robust capability to adjust and cope with these frequency changes, maintaining a higher average vibration reduction of around 55–60%. Consequently, STMDs emerge as a necessary solution for very slender structures where HSI significantly alters the global frequency response. This study highlights the importance of considering HSI in the design and implementation of damping solutions to ensure optimal functionality and user comfort on lightweight pedestrian bridges.

A semi-floating cable-stayed bridge can swing longitudinally to absorb seismic energy in an earthquake for the purpose of reducing structural response. However, the large transverse (lateral) seismic response of such large-span cable-stayed bridges must be controlled to avoid severe bridge damage and ensure train safety. This study investigates the dynamic response and associated damping mechanism of a coupled high-speed rail (HSR) vehicle and cable-stayed bridge system subjected to various ground motions. A comprehensive vehicle–track–bridge interaction system is first established. Then, the dynamics of a semi-floating cable-stayed bridge-HSR vehicle system equipped with magnetorheological bearings (MRBs) and fluid viscous dampers (FVDs) is examined with various inputs of near-fault (NF) pulse-type, NF non-pulse-type, and far-field (FF) ground motions. To effectively mitigate the bridge internal force response and enhance train running safety, the transverse and longitudinal FVDs need to be concurrently utilized along with MRBs. This research presents a novel mitigation approach for simultaneously reducing the transverse vibrations of cable-stayed bridge and the derailment risk of running train.

Stay cables are becoming slender and their fundamental frequencies are becoming lower with the span of bridges increasing, thus leading to the occurrence of multi-modal vibration under various excitations. As a simple and effective strategy for cable vibration mitigation, the external damper is widely used in practice. However, one damper normally can target only fewer modes and poses limited effects on the control of multi-modal vibration. This paper proposed the use of a joint control system combining a viscous damper and a tuned mass damper for mitigating the multi-modal vibration of stay cables, followed by the optimization methodology of tuning and positioning. The control performance of the joint system was evaluated by numerical simulations. The feasibility of the joint control system was validated by analyzing the results of the comparative study, therefore providing a possible solution to multi-modal and high-modal vibration of stay cables.

Compared with tuned mass damper, tuned inerter damper (TID) has higher damping efficiency and lightweight characteristic if appropriate optimal methods are selected. Generally, $H_{\infty }$ or $H_2$ optimal methods are adopted to determine the optimal parameters of TID individually. But the vibration mitigation performance of the TID under near resonance frequency band based on $H_{\infty }$ optimization is less than $H_2$ optimization, but the peak frequency response based on $H_2$ optimization will be greater than $H_{\infty }$ optimization at the same time. Dual-characteristic-based vibration control may not be achievable based on $H_{\infty }$ or $H_2$ criteria, respectively. For this reason, hybrid $H_2/H_{\infty }$ optimization can be adopted. In this work, closed-form expressions are derived for the control of structural displacement responses based on hybrid $H_2/H_{\infty }$ optimal method. The vibration mitigation performance of the different optimized TIDs is evaluated considering the single-degree-of-freedom and multi-degrees-of-freedom systems are subjected to typical ground motions excitation. Results illustrate that because of the use of the optimal stiffness ratio of $H_{\infty }$ optimization and very close value of $H_2$ optimizations’ nominal damping ratio in $H_2/H_{\infty }$ optimization, $H_2/H_{\infty }$ optimization shows ‘dual characteristics’ in different excitation situations. Specifically, the peak response and structural fundamental frequencies’ response in displacement frequency response function using hybrid $H_2/H_{\infty }$ optimal methods are between $H_2$ and $H_{\infty }$ optimization, which indicates an excellent and balanced control performance combining the advantages of $H_2$ and $H_{\infty }$ optimal solutions. Hence, this hybrid method is more suitable for more complex ground motions excitation to control critical structural responses instead of single characteristic excitation. And the comprehensive vibration control in dynamic time histories analyses can be achieved by this dual characteristic-based optimal strategy. When designing the specific TID, hybrid $H_2/H_{\infty }$ optimization can be considered as the best choice for its compatibility and high adaptability for complex practical engineering scenarios with random and diverse excitations.

With the rapid development of urban rail transit, the environmental vibration and secondary noise induced by metro train operation have become increasingly serious, posing stricter requirements on the vibration and secondary noise of sensitive building office (SBO) and sensitive building school (SBS). To predict and control the vibrations and secondary noise in sensitive buildings along the metro line induced by metro train operations. A prediction method for the vibration and secondary noise of sensitive buildings along the metro line during metro train operation has been proposed. The sub-model of train-track system coupled dynamics and the sub-model of track-tunnel-soil-building system dynamics are included. The influence of metro train operation on the vibration and secondary noise of SBO and SBS is studied. The influence of the distance between the metro line and the building on the vibration and secondary noise of the sensitive building is discussed, and an effective control scheme of vibration and secondary noise is proposed. Results show that the vibration frequencies of the SBS and the SBO caused by the metro train operation are concentrated at about 8Hz and 63Hz. The vibration below the second floor of SBO caused by the metro train operation exceeds the limit, and the secondary noise below the third floor of SBS exceeds the limit. The secondary noise inside the building of each floor of SBO exceeded the limit. Using secondary noise to evaluate the environmental impact of metro train operations is more stringent than relying solely on vibration assessments. secondary noise is recommended in engineering to assess the impact of metro train operation on sensitive buildings along line. Combined with vibration, secondary noise and construction requirements, SBS and SBO are recommended to be no less than 72m and 74m away from the metro line, respectively.

Negative stiffness dampers (NSDs) have garnered significant attention in the research of base-isolated structures (BIS). This study proposes a tuned negative stiffness viscous mass damper (TNSVMD), which includes a tuning spring in series with the NSD and an inerter, to enhance the seismic control effect of the BIS. An analytical model of a BIS with the TNSVMD is initially established, followed by an investigation into frequency response analysis. The analytical expressions for the stochastic responses of the BIS with TNSVMD are derived, and further exploration is conducted on the influences of the negative stiffness ratio, dashpot damping ratio, and inerter mass ratio on the stochastic responses of the BIS. The mechanisms responsible for the damping enhancement and energy dissipation enhancement of the BIS with the TNSVMD are elucidated through the derivation of the analytical solution for the effective damping ratio and dissipated energy of the BIS with the TNSVMD. Two principles are utilized to determine the optimal parameters of the TNSVMD. These principles involve minimizing the earthquake input energy ratio of the BIS and minimizing the stochastic displacement response of the BIS. Finally, the effectiveness of the TNSVMD is validated through a design example using 100 ground motions. The results indicate that the displacement and acceleration responses of the BIS can be simultaneously controlled due to the weakening of stiffness and enhancement of the effective damping ratio, leading to higher energy dissipation efficiency of the TNSVMD. The increase in the inertial mass ratio enhances the seismic mitigation effect and reduces the optimal negative stiffness ratio and optimal dashpot damping ratio. Therefore, it raises the possibility of implementing the TNSVMD. The inherent damping ratio of the BIS has a significant impact on the control efficiency of the TNSVMD. For BIS systems with relatively small inherent damping ratios, the TNSVMD can achieve better control effectiveness.

An inerter system, based on electromechanical similarity theory and vibration mitigation and isolation technology, represents a category of vibration damping systems. These systems typically improve damping performance by increasing mass or inertia, a method often found to be inefficient, leading to inadequate damping and limited applicability in real-world engineering scenarios. The lightweight inerter system (LwIS) introduced herein offers a more flexible and efficient means of altering structural inertia. Initially, this paper establishes the motion control equations for LwIS, followed by a stochastic analysis to derive the analytical expression for the root mean square displacement under Gaussian white noise excitation. A parametric analysis of LwIS is subsequently conducted, developing a displacement-based parametric strategy. Design examples for single-degree-of-freedom (SDOF) engineering structures under various requirements are provided, demonstrating the validity of LwIS’s optimal parameters through responses to simple harmonic excitation and seismic impacts. The findings indicate that the optimization approach of LwIS, unlike traditional methods, simultaneously addresses the displacement performance of the primary structure and the deformation efficiency of the damping element, thereby facilitating comprehensive optimization. Four optimal design parameters for LwIS are identified, underscoring its applicability to stochastic excitation and a broader range of load cases, thus enhancing its practicality in engineering contexts. LwIS’s design philosophy aims to improve deformation efficiency through an increased deformation enhancement coefficient in the damping element, enhancing damping performance, controlling seismic responses, and achieving superior energy dissipation. The optimal parameters, smaller in value, maximize the potential of the inerter system, aligning with the dual objectives of performance optimization and lightweight design, consequently reducing engineering costs.

Particle damping technology is a widely used passive vibration control method known for its simplicity and efficiency in engineering applications. This study applies a Particle Damper (PD) to reduce low-frequency vibrations in a manipulator. A novel coupled dynamic model of the PD and manipulator is developed, considering the impact of low-frequency vibrations. To address the challenges posed by the nonlinear behavior of particles, Discrete Element Method (DEM) simulations using EDEM software are performed to investigate the effects of key factors, such as particle packing density, diameter, and material composition, on energy dissipation. The simulation results are validated through experiments, with the manipulator serving as the controlled object to assess the PD’s control performance. The PD design is further refined by incorporating multi-layer baffles, which enhance energy dissipation and improve the suppression of vibrations. The results demonstrate that the optimized PD system effectively reduces the manipulator’s low-frequency vibration response. By integrating simulations, experimental validation, and structural optimization, this study provides deeper insights into particle damping mechanisms and offers innovative solutions for vibration control in manipulators and similar engineering systems.

Vibration in wind turbine towers poses a significant threat to the service life and structural integrity of wind turbines. Dampers have been identified as a pivotal strategy for alleviating such vibrations. Despite this, the dynamic behavior of large-scale offshore wind turbines is frequently swayed by wind shear, the tower shadow effect, and the Rotor-Nacelle Assembly (RNA) control system, typically manifesting as responses to the blade passing frequency (3P). To mitigate these vibrations, this study introduces a 3P tuning method for tuned mass dampers (TMDs), alongside a sophisticated design approach that targets optimal frequency and damping ratios. The integration of a semi-active variable-tuned mass damper (SA-V-TMD) offers a dual-mode control solution: The “3P tuning mode” adeptly manages vibrations across a spectrum of operating conditions, while the “1st modal frequency tuning mode” stabilizes the structure during parked states. Simulations substantiate the 3P tuning method’s enhanced efficacy over standard methods under operational conditions. Furthermore, the SA-V-TMD demonstrates superior effectiveness and stability in comparison to traditional TMDs, underscoring its potential as a preeminent solution in wind turbine vibration management.

To improve the operational adaptability of high-speed trains, a control method is proposed to mitigate carbody lateral vibration by leveraging the dynamic vibration absorption effect of multi-suspended equipment. A comprehensive analysis of five typical wheel/rail contact relationships, closely related to vehicle operational status in the long-term service, is conducted and incorporated into the established rigid-flexible coupling dynamic model. Based on the proposed improved niche genetic algorithm (INGA), an objective function, which holistically assesses the vibration of the carbody and suspended equipment, is constructed to undertake the optimization analysis. The results show that the dynamic vibration absorption effect of the suspended equipment proves effective in controlling carbody lateral vibration, thereby enhancing operational adaptability. However, the improvement in vehicle performance varies under different operating conditions, influenced by the competitive relationship between multiple control objectives. While carbody lateral vibration performance could be further improved without considering equipment vibration tolerance, such improvements are limited, indicating that it is reasonable and necessary to consider equipment vibration tolerance in the research of carbody vibration control. This study furnishes valuable insights for improving the adaptability of high-speed train operations and provides ideas for further research on carbody vibration control using the suspended equipment.

The vibrational response amplitudes reduction is investigated for the axially moving composite cantilever rectangular (AM-CCR) laminated plate subjected to the transverse and parametric excitation by using the nonlinear energy sink (NES). Three different NES installed methods which are one NES, two NESs in series and two NESs in parallel are compared for the vibration attenuation of the AM-CCR laminated plate. For the dynamic model of the AM-CCR laminated plate with transverse and parametric excitation, using the first-order shear deformation theory, the von Karman large deformation theory, Hamilton’s principle, and the Galerkin discrete technique, the ordinary differential motion equations of the system are obtained. The pseudo frequencies and the nonlinear vibrational behaviors are depicted for the AM-CCR laminated plate. The nonlinear dynamic motion equations are established for the AM-CCR laminated plate with one NES, two NESs in series and two NESs in parallel are derived, respectively. The comparisons are given for vibrational response amplitude attenuation of the different locations in which the NES is placed on the end of the plate under the various retractable velocities. In addition, the influences of the number and the series and parallel connections of the NESs on the vibrational response reduction of the AM-CCR laminated plate are studied by the simulation method. When the AM-CCR laminated plate contracts, the scheme attached NESs in series has the optimal effect of the vibration reduction. When the AM-CCR laminated plate extends, the scheme with NESs in parallel has better effectiveness for the vibrational response reduction

Wind Turbine Towers (WTTs) are slender infrastructures for renewable energies, which are subjected to significant vibrations induced by wind and seismic hazards during their lifetime. In order to suppress these harmful vibrations, an Inerter-based Outrigger-Cable-Lever-Damping (IOCLD) system is proposed. It is composed of an outrigger, a lever, and a pair of cables and inerter-dashpot dampers. The outrigger is to convert bending rotation into vertical vibrations, which is transferred to the lever by the cables. The lever amplifies the inertial-damping force provided by the dampers. The inerter is beneficial to enhance energy dissipation. With these mechanisms, the vibration of WTTs can be effectively suppressed. In order to achieve optimal control performances, the tuning parameters of the IOCLD are analytically derived. Additionally, an equivalent inertance ratio is proposed to obtain the optimal parameters and evaluate the control performance. Finally, through practical numerical cases for wind- and seismic-induced vibration control, the effectiveness of the IOCLD is proved. Compared with existed Amplifying Damping Transfer System (ADTS) without inerters, IOCLD exhibits an excellent energy dissipation rate, which exceeds twice of ADTS for the investigated cases. Compared with conventional Tuned Mass Damper (TMD), IOCLD shows its advantages for lightweight, stability and in-situ adjustable feasibility.

The nonlinear dynamics of a vibration-controlled magnetic system are studied via a three-mode discretization of the governing partial differential equations. The analysis focuses specifically on the effects of modal coupling through the nonlinear terms of the system equation. A bifurcation analysis of the system is performed using sophisticated nonlinear theories, including the center manifold theory and the normal form theorem. The results show that when the first mode and the higher modes are excited simultaneously by the control forces, the three-mode approximation method predicts the existence of a triple zero degeneracy accompanied by complicated bifurcation phenomena. Comparing the dynamics structure predicted by the three-mode approximation model with that obtained from a single-mode approach, it is found that if the higher modes are excited by the control forces, the effects of modal coupling should be taken into consideration since a complicated dynamics structure may exist as a result.

The lever-type multiple tuned mass dampers (LT-MTMD), consisting of several lever-type tuned mass dampers (LT-TMDs) with a uniform distribution of natural frequencies, are proposed for the vibration control of long-span bridges. Using the analytical expressions for the dynamic magnification factors (DMF) of the LT-MTMD structure system, an evaluation, with inclusion of the LT-MTMD stroke, is conducted on the performance of the LT-MTMD with identical stiffness and damping coefficients but unequal masses for mitigating harmonically forced vibrations. The LT-MTMD is found to possess the near-zero optimum average damping ratio regimen when the total number of dampers exceeds a certain value. In comparison, the LT-MTMD without the near-zero optimum average damping ratio and the traditional hanging-type multiple tuned mass dampers (HT-MTMD) without the near-zero optimum average damping ratio can achieve approximately the same optimum frequency spacing (an indicator for robustness), effectiveness, and stroke. Compared with the HT-MTMD, the LT-MTMD needs lesser optimum average damping ratio but significantly higher optimum tuning frequency ratio. Its main advantage is that the static stretching of the spring may be adjusted to meet the practical requirements through the support movement, while maintaining the same robustness, effectiveness, and stroke. Consequently, the LT-MTMD is a better choice for suppressing the vibration of long-span bridges as the static stretching of the spring required is not large.

The multiple dual tuned mass dampers, referred to as the MDTMD, consisting of several units of dual tuned mass dampers (DTMD) are proposed for the first time herein, aimed at the effectiveness and robustness of the system for suppressing the undesirable vibrations of structures under the ground acceleration. The total number of dampers can be arbitrary and their natural frequencies are uniformly distributed. Ten typical types of the MDTMD can be devised by varying the system parameters. Employing the criteria chosen for optimum searching, parametric studies were carried out to evaluate the performance of the MDTMD of Type I-1 for its convenience in manufacturing, in which the larger mass blocks (LMBs) are assumed to have identical stiffness, but unequal masses, and the smaller mass blocks (SMBs) have identical stiffness and damping coefficient, but unequal masses and damping ratios. By adopting the maximum dynamic magnification factor (DMF) for each LMB and SMB used in estimating the stroke, an evaluation is also made for the stroke of the MDTMD. The numerical results indicate that the MDTMD (I-1) can provide better effectiveness and higher robustness in comparison with the dual tuned mass dampers (DTMD) and other MTMD systems of similar complexities. However, the stroke of the MDTMD is greater than that of the DTMD and the stroke of each SMB in the MDTMD is larger than that of the mass blocks (MBs) in the arbitrary integer and odd number based MTMD.

The dual-layer multiple tuned mass dampers (DL-MTMD) with a uniform distribution of natural frequencies are proposed, which consist of one large tuned mass damper (L-TMD) and an arbitrary number of small tuned mass dampers (S-TMD). The structure is represented by a generalized system corresponding to the specific vibration mode to be controlled. The criterion for assessing the optimum parameters and effectiveness of the DL-MTMD is based on the minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure installed with the DL-MTMD. Also considered is the stroke of the DL-MTMD. The proposed DL-MTMD system is demonstrated to show higher effectiveness and robustness to the change in frequency tuning, in comparison to the multiple tuned mass dampers (MTMD) with equal total mass ratios. It is also demonstrated to be more effective than the dual tuned mass dampers (DTMD) with one large and one small tuned mass damper, but they maintain the same level of robustness to the change in frequency tuning. The DL-MTMD system can be easily manufactured as the optimum value for the linking dashpots between the structure and L-TMD is shown to be zero.

In this paper, the dynamic performance of a controlled high building is numerically investigated considering the effects of different numbers of mass dampers and their interconnection. The numerical analysis is conducted on a 20-story building considered as a shear frame and reduced to an SDOF system by means of the mode-superposition method. The system is subjected to harmonic load. Numerical searches are conducted based on the Min. Max. procedure in order to obtain efficient interconnected (I) multiple tuned mass dampers (MTMD). Comparisons are made among the uncontrolled system, the system controlled by non-interconnected (NI) MTMD, and the system controlled by (I) MTMD in frequency and time domain. Both (NI) and (I) MTMD reduce significantly frequency response peak amplitude. It is observed that the (I) MTMD produces great reductions on maximum displacement, rms displacement, steady-state peak response, and story displacements close to the reductions obtained by (NI) MTMD using review parameters. Mass maximum displacements analysis shows that the space required for (I) MTMD installation is smaller than (NI) MTMD.

Active multiple tuned mass dampers (AMTMDs) consisting of several active tuned mass dampers (ATMDs) with uniform distribution of natural frequencies have been proposed for vibration mitigation of structures under wind loads. In this regard, the optimum parameter criterion is defined as the minimization of the root-mean-square (RMS) displacement and acceleration responses of the structure with the AMTMD. Meanwhile, the effectiveness criterion is defined as the ratio of the minimum RMS displacement and RMS acceleration of the structure with the AMTMD to those without the devices, respectively referred to as the displacement and acceleration reduction factors (DRF and ARF). With these two criteria, the influences of the selective parameters on the effectiveness and robustness of the devices for vibration control under wind loads are studied. In addition, the stroke of the AMTMD is examined by quantitatively assessing the RMS displacement of each ATMD. Results indicate that in comparison with a single ATMD, the AMTMD can cause more reduction in the displacement and acceleration responses of the structure under wind loads. The stroke of the AMTMD is greater based on the ARF than the DRF criterion. In particular, the simulation results in the time domain confirm that by resorting to the AMTMD, a large control force can indeed be decentralized into many smaller control forces without losing the level of response reduction.

Structural optimization and vibration control have long been recognized as effective approaches to obtain the optimal structural design and to mitigate excessive responses of tall building structures. However, the combined effects of both techniques in the structural design of wind-sensitive tall buildings with excessive responses have not been revealed. Therefore, this paper develops an integrated design technique making use of both the advantages of structural optimization and vibration control with an empirical cost model of the control devices. While the structural optimization is based on a very efficient optimality criteria (OC) method, a smart tuned mass damper (STMD) is used for the structural control purposes. Utilizing data obtained from synchronous pressure measurements in the wind tunnel, a 60-story building of mixed steel and concrete construction with three-dimensional (3D) mode shapes was employed as an illustrative example to demonstrate the effectiveness of the proposed optimal performance-based design framework integrating with structural vibration control.