Abstract ：

通过减震措施降低核安全壳地震加速度响应,确保强震作用下核电设备的安全,对提高核安全壳抗震韧性具有现实意义.调谐质量阻尼器(tuned mass damper,TMD)能有效地降低风振响应,用于控制地震响应,存在频带窄、减震效率低等不足.文中将TMD与惯容结合,提出采用调谐质量惯容阻尼器(tuned mass damper inerter,TMDI)降低核安全壳地震加速度.基于性能需求设计思想与H∞优化准则建立了TMDI最优参数设计方法.在此基础上,使用子结构思想联合 ABAQUS与Matlab开发了数值模拟方法,实现了TMDI控制下核安全壳地震响应有限元模拟.通过对某核安全壳有限元模型进行TMDI地震控制算例分析,验证了理论分析的有效性.结果表明,采用TMDI时核安全壳顶部峰值加速度减震率为 46.1%,且TMDI达到相同减震指标时所需调谐质量减少了28.2%.

Keyword ：

地震响应 调谐质量惯容阻尼器 核安全壳 惯容 轻量化设计

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Abstract ：

Seismic isolators have been extensively utilized in the field of structural vibration control due to their superior control effectiveness in reducing absolute acceleration responses. However, this effectiveness comes with a compromise on large isolation deformation, which may result in various issues, such as pounding and/or unseating damages of bridge decks. To address these issues, a negative stiffness enhanced tuned mass damper (NS-TMD) was proposed, aiming to minimize absolute acceleration while simultaneously limiting isolation deformation, and its control effectiveness has been demonstrated. However, the previous studies primarily focused on single-objective optimization without considering NS-TMD stroke, and the conventional negative stiffness (NS) devices, e.g., the pre-compressed helical springs with revolute joints, could not be well compatible with NS-TMD due to limited operating range. To this end, this study proposes a novel NS-TMD, which consists of a TMD with a curved-type mass block and an NS element based on a cam-roller-spring (CRS) mechanism. The working mechanism of the novel NS-TMD is first introduced, and its mechanical model is formulated. This novel system is then applied to a typical isolated bridge to illustrate its control effectiveness. Equilibrium equations and state space formulations of the system are derived. Subsequently, parametric analysis on NS-TMD is performed, followed by the proposal of a multi-objective optimization strategy to simultaneously minimize the relative displacement of the bridge deck and the stroke of NS-TMD. Finally, the control performance of NS-TMD is systematically evaluated. Numerical results show that the optimized NS-TMD not only reduces the deck displacement of the bridge system (with a maximum reduction ratio of 49.50 %) but also decreases its absolute acceleration. Furthermore, NS-TMD can achieve superior control performance in terms of the deck displacement, while limiting the stroke within a reasonable range. In summary, NS-TMD is a highly efficient alternative to conventional TMDs in terms of control effectiveness and feasibility. © 2024 Elsevier Ltd

Keyword ：

Vibrations (mechanical) State space methods Bridge decks Damping Earthquakes Induced Seismicity Seismic response

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Abstract ：

Vortex-induced vibration (VIV) of long-span bridges is frequently observed in various types of bridges at low or medium wind speeds, causing disruption of traffic, fatigue issues of the bridge, and even panic in society. This study compares the VIV mitigation performance of the conventional tuned mass damper (TMD) and three novel damping devices, i.e. the negative-stiffness damper (NSD), inerter-based damper (IBD), and nonlinear energy sink (NES). The governing motion equations of four damper-bridge systems are established, and the optimal parameters of each damper are obtained. The semi-analytical solutions of controlled responses in the frequency domain are derived using the harmonic balance method (HBM). These four dampers are applied to mitigate the VIV of a parallel box girder bridge, which was observed and studied in the wind tunnel tests. Their performance is examined using semi-analytical solutions in the frequency domain and numerical solutions in the time domain based on the Runge-Kutta method, respectively. The control efficiency, the stroke of the auxiliary block, and the robustness of these four systems are compared. The strengths and weaknesses of different dampers used for VIV mitigation in bridge girders are discussed. The findings of this study provide the basis for determining the most favorable damper devices for VIV mitigation to adapt the specific requirements of different bridges.

Keyword ：

nonlinear energy sink negative-stiffness damper Bridge VIV mitigation inerter-based damper tunned mass damper

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Abstract ：

The development of surface-enhanced Raman spectroscopy (SERS) as an ultrasensitive fingerprint analysis technique in precision medicine requires high-performance SERS substrates with controllable nanostructure (hot-spot) distribution, simple fabrication, superior stability, biocompatibility, and extraordinary optical responses. Unfortunately, fabrication of arbitrary nanostructures with high homogeneity on a large scale for SERS is still challenging. Herein, we report an ultrafast laser parallel fabrication protocol for Au/2D-transition-metal dichalcogenide hybrid SERS biosensors. The leveraged photonic nanojets (PNJs) are generated by a micron-sized microsphere monolayer to simultaneously trigger localized phase transition in 2H-MoTe2, achieving a 1T′-MoTe2 nanopattern array with a density of 1 million per mm2 by a single laser shot. The Au nanoparticle clusters (AuNCs) are subsequently grown in situ from the 1T′ regions, creating a AuNCs on 1T′/2H-MoTe2 (AuNCs@1T’/2H-MoTe2) hybrid SERS substrate. The fabricated feature diameter and overlay accuracy of the patterned AuNCs are 210.1 ± 3.4 and 9.2 ± 1.7 nm, respectively. To eliminate background noise, we designed dimer-AuNCs@1T′/2H-MoTe2 (dAuNCs@1T′/2H-MoTe2), achieving a detection limit of 10-13 M with an enhancement factor of 4.9 × 108 for the methylene blue (MB) analyte. The strong localized surface plasmon resonances in the dAuNCs as well as efficient charge transfers between Au, 2H-MoTe2, and MB contribute to the majority of Raman enhancement. The multiscale dAuNCs@1T′/2H-MoTe2 array provides a powerful SERSome (comprising multiple SERS spectra) platform for therapeutic drug monitoring, by which we successfully identified the metabolic behaviors of living gastric adenocarcinoma cells administered with two drugs, i.e., capecitabine, oxaliplatin, and their combination. The present work establishes opportunities for creating a highly ordered nanopattern array for ultrasensitive SERSome analysis of cell metabolism in cancer therapy. © 2025 American Chemical Society.

Keyword ：

therapeutic drug monitoring femtosecond laser surface-enhanced Raman spectroscopy (SERS) phase-transition engineering 2D-transition-metal dichalcogenide (2D-TMD)-based hybrid substrate metal nanostructure biosensor

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Abstract ：

Traditional seismic isolators, such as the friction pendulum system (FPS), exhibit high isolation efficiency during slight-to-moderate earthquakes, but their ability to constrain isolation deformations under severe earthquakes remains limited. The negative stiffness enhanced tuned mass dampers (NS-TMDs), which exist in two configurations (NS-TMD I and NS-TMD II), have been successfully employed to improve the seismic performance of isolated bridges. However, previous studies have focused primarily on the control performance of NS-TMDs in simplified linear systems, without considering structural nonlinearities. To address this gap, this paper explores the effectiveness of using NS-TMDs for the seismic protection of bridges isolated with a FPS, and proposes a stability-based optimization strategy for NS-TMDs. In particular, the working mechanism and mechanical model of NS-TMDs are first introduced. The control devices are integrated into a FPS-isolated single-degree-of-freedom (SDOF) system. For this system, the nonlinear equilibrium equations are formulated, and a stochastic linearization analysis is performed. Subsequently, a stability-based optimization strategy is proposed for NS-TMDs and their control performance under stationary excitation is examined. Finally, a comprehensive analysis on the control effectiveness of NS-TMDs in the FPS-isolated bridge under non-stationary excitation is conducted. The results show that the optimized NS-TMDs could enhance the isolation efficiency of FPS while effectively constraining isolation deformation within a limited range under both far-field and near-fault earthquakes. In addition, NS-TMD I demonstrates greater effectiveness in reducing deck acceleration than deck displacement, whereas NS-TMD II exhibits the opposite trend. Overall, NS-TMDs provide an effective vibration control solution for improving the seismic performance of FPS-isolated bridges.

Keyword ：

Negative stiffness enhanced tuned mass damper Control performances Nonlinear isolated bridge Friction pendulum system Optimization

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Abstract ：

With the ever-growing of span length, the safety factor of flutter for long-span bridges, i.e., the ratio between the critical flutter wind velocity and flutter checking velocity, has become increasingly less. Utilizing mechanical devices as a supplemental measure to the aerodynamic measures has become a solution for enhancing the flutter performance of long-span bridges. In this study, the inerter-based dynamic vibration absorbers (IDVAs), featured by light-weight and broadband properties, are employed to improve the flutter performance of long-span bridges and are compared with conventional tuned mass damper (TMD). A numerical optimal design method for the bridge-IDVA systems under flutter is first proposed. Then, the performance of the control systems subjected to the uncertainty of flutter derivatives as well as hard and soft types of flutter is systematically investigated. Compared with TMD, utilizing IDVAs can not only increase the critical flutter wind velocity, but also reduce the failure probability after considering the uncertainty of flutter derivatives. When the flutter of a bridge is characterized by soft type, the advantages of the IDVAs will become more significant. The findings in this research can contribute to the flutter control of long-span bridges and promote the application studies of inerter-based devices.

Keyword ：

Dynamic and sensitivity analysis Long-span bridges Flutter control Optimal design Inerter-based dynamic vibration absorbers

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Abstract ：

Nonlinear energy sinks (NESs) have emerged as a promising solution to overcome the narrow effective bandwidth of linear dynamic vibration absorbers such as the tuned mass damper (TMD). In particular, track NESs are increasingly attracting attention as they are capable of generating nonlinear restoring forces by the movement of an additional mass on the curved tracks. The present study aims to investigate and explore the versatile characteristics of track NESs in structural vibration control. To this end, three different track profiles are considered, namely the profiles designed by a quartic term only, by combined positive quadratic and quartic terms, and by combined negative quadratic and positive quartic terms. Their profiles and damping coefficients are analytically derived in closed form. The frequency response functions of standalone track NESs are constructed using the Harmonic Balance Method and compared with those obtained by the 4th-order Runge-Kutta method, and the dynamic responses, including the displacements, the phase planes, the nonlinear stiffness forces, and the vibrational frequencies, of the track NESs are presented and discussed under different excitation amplitudes and frequencies. The effectiveness and robustness of using track NESs for structural vibration control are also systematically investigated and compared with TMD under harmonic and white-noise ground excitations. Results show that the closed-form solutions of optimal profile and damping coefficients are sufficiently accurate for lightly damped structures, and the frequency response functions of track NESs can be accurately estimated using the Harmonic Balance Method for low and moderate excitations, although their dynamic responses are sensitive to the excitation amplitudes and frequencies. Furthermore, in comparison to TMD, the track NESs are superior in terms of decreased stiffness and smaller working strokes. In general, the present study demonstrates the potential of using track NESs as an effective and robust alternative for structural vibration control.

Keyword ：

Frequency response function Harmonic balance method Track nonlinear energy sink Dynamic characteristic Vibration control effectiveness

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Abstract ：

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. © 2024 The Authors

Keyword ：

Offshore wind turbines Self-powered active mass dampers Vibration control Energy harvesting

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Abstract ：

Negative stiffness element has been applied to improve the control performance of tuned mass dampers (TMDs) recently, and two tuned mass dampers enhanced with negative stiffness (TMD-NS) element, namely KDamper (Without loss of generality, it is referred to as TMD-NS I in the present study) and Extended KDamper (EKD, TMD-NS II), have been developed. Previous studies have demonstrated the control effectiveness of TMD-NS I and II. However, there still exist some issues to be addressed: (1) previous studies normally optimize TMD-NS via the intricate and time-consuming numerical methods, the analytical solutions for the optimal design parameters of TMD-NS II remain unknown; (2) a comprehensive and exhaustive evaluation that compares the control effectiveness of TMD-NS I and II is absent from existing literature. To fill these research gaps, this study derives closed-form optimum solutions for TMD-NS II using the H∞ approach. The control effectiveness of TMD-NS I and II in suppressing the seismic responses of structures is investigated systematically. Specifically, the analytical model of an undamped SDOF system equipped with TMD-NS I or II is first developed within a unified framework, and corresponding dynamic equations of motion are formulated. Subsequently, the optimal parameters of TMD-NS I and II are derived based on the classical “fixed-point” theory. Based on the derived optimal parameters, the control effectiveness of TMD-NS I and II are examined by using a damped SDOF system subjected to harmonic excitations and real earthquake ground motions. Finally, a 5-storey isolated benchmark building model is adopted to further investigate the effectiveness of TMD-NS in the seismic protection of engineering structures. The results reveal that the derived closed-form solutions are accurate in capturing the optimal parameters of TMD-NS. In addition, both the optimized TMD-NS I and II outperform the conventional TMD in reducing the seismic responses of structures. Furthermore, TMD-NS I proves more effective in reducing the absolute acceleration of the isolated building, whereas TMD-NS II demonstrates better performance in mitigating the isolating deformation. In a nutshell, both the TMD-NS I and II are highly effective alternatives to conventional TMDs, showcasing superior performance in vibration reduction and robustness. © 2024 Elsevier Ltd

Keyword ：

Control effectiveness KDamper Extended KDamper Isolated structures Closed-form optimum solutions

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Abstract ：

Due to the problem that the tuned mass damper (TMD) system is easy to be off-tuned when applied to light structures, which leads to the decline of vibration reduction effect, a new shape memory alloy semi-active TMD system is designed in this paper. The system uses steel cables to suspend the mass to bear all its weight. Large shape memory alloy bars with rectangular effective cross sections are used to provide different bending stiffness in the two directions of the TMD system in the horizontal plane. In order to study the semi-active performance of the system, a full-scale shape memory alloy TMD system was subjected to free vibration tests in this paper. By changing the working temperature of the shape memory alloy, the influence of temperature change on the frequency and damping ratio of the TMD system was studied. The test results show that by controlling the working temperature of the shape memory alloy from -40 益 to 80 益, the frequency of the TMD system shows an increasing trend with temperature increases, while the damping ratio shows a decreasing trend with the temperature increases. The results show that the new shape memory alloy semi-active TMD system is applied to controlled structures, and once the TMD is off-tuned, it can be re-tuned by changing the temperature of the shape memory alloy. Therefore, the new shape memory alloy TMD system designed in this paper has certain engineering application value and prospect for the study of light structure vibration reduction. © 2024 Editorial office of Earthquake Engineering and Engineering Dynamics. All rights reserved.

Keyword ：

off-tuned tuned mass damper(TMD) semi-active control vibration control shape memory alloy (SMA)

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