Experimental and numerical studies of a novel asymmetric nonlinear mass damper for seismic response mitigation

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Nonlinear energy sinks (NESs) have outperformed tuned mass dampers in mitigating undesired responses against changes in structural frequencies. However, the dilemma of gaining frequency robustness at the cost of energy sensitivity as well as the large masses of devices required for civil engineering structures impede the applications of existing NESs. To solve the issue of lacking energy robustness and take advantage of inerters to reduce physical mass, an asymmetric NES‐inerter (Asym NESI) is developed in this study. This passive inerter‐based nonlinear mass damper is configured based on an energy‐robust NES with an inerter added between the auxiliary mass and a fixed point. The paper commences with the formulation of the Asym NESI through mathematical derivations. Then an Asym NESI is designed and evaluated on a three‐story structure in comparison with other counterpart mass dampers. The effectiveness of the Asym NESI can be attributed to its unique dynamics which are revealed analytically using the harmonic balance method through free vibrations and harmonically forced vibrations. The ensuing numerical validations show that due to the integrated linear and nonlinear dynamics of the Asym NESI, the proposed device exhibits strong robustness against changes in both structural frequency and energy level. Moreover, driven by the large inertial effect induced by the auxiliary inerter, the Asym NESI shows flexibility in choosing a practical installation location without sacrificing excellent control capacity. Importantly, the benefits of the Asym NESI are further confirmed by the responses subjected to a suite of ground motions. This study provides analytical insights into the effectiveness and robustness of Asym NESIs and demonstrates substantial performance enhancement by the inerter in structural response mitigation.

Section: Introductionmentioning

confidence: 88%

“…The Asym NESI consists of an Asym NES 32 and an inerter. The two terminals of the inerter are connected to the auxiliary mass and the ground, respectively.…”

Section: Formulation Of Asym Nesimentioning

confidence: 99%

Section: Design Of Asym Nesimentioning

confidence: 99%

(m + b) \ddot{x} + c \dot{x} + F_{normalA} = - (m + b) {\overset{x}{true}}_{3} - m {\overset{x}{true}}_{normalg}

M_{normals} {\overset{x}{true}}_{normals} + C_{normals} {\overset{x}{true}}_{normals} + K_{normals} x_{normals} = [\begin{matrix} G_{normalg} & G_{normalA} \end{matrix}] \{\begin{matrix} {\overset{x}{true}}_{normalg} \\ c \overset{x}{true} + F_{A} \end{matrix}\}

where M s , C s , and K s are the mass, damping, and stiffness matrices of the primary structure, respectively,

x_{normals} = {[\begin{matrix} x_{1} & x_{2} & x_{3} \end{matrix}]}^{normalT}

and x i is the displacement of the i th story relative to the ground, and

G_{normalg} = - diag false(M_{s} false)

and

G_{normalA} = {[\begin{matrix} 0 & 0 & 1 \end{matrix}]}^{normalT}

are the influence matrices for the ground motion and the forces of the Asym NESI, respectively.…”

Section: Design Of Asym Nesimentioning

confidence: 99%

Section: Design Of Asym Nesimentioning

confidence: 99%

See 3 more Smart Citations

Effectiveness and robustness of an asymmetric nonlinear energy sink‐inerter for dynamic response mitigation

Wang

Zhang

et al. 2021

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Experimental validation, analytical investigation, and design method of tuned mass damper‐clutching inerter for robust control of structures

Wang

Zheng

2022

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Inerters have significantly uplifted the cost‐effectiveness of structural control technologies. A recently proposed tuned mass damper‐clutching inerter (TMDCI) takes advantage of both mass amplification effect and energy absorption capacity of inerter which is more effective and practical than its predecessors. However, the existing study only provided numerical demonstrations while experimental evidence and analytical explanation are still lacking for in‐depth understanding of the dynamic properties and working principles of TMDCIs. In this study, the mathematical descriptions of TMDCIs are first developed and experimentally validated on a three‐story structure. The validated model is then used to analyze the influences of inerter arrangement and total inertance in inerter‐enhanced devices. With an appropriate inerter arrangement and inertance, the TMDCI shows excellent control performance regardless of the changes in the structural frequency. The reason for the strong robustness of TMDCIs is then revealed via analytical investigation of standalone TMDCIs; the harmonically forced steady‐state responses manifest that the TMDCI can be linearized as equivalent tuned mass damper‐inerters with variable parameters whose natural frequency increases with the increase of excitation frequency. Based on the analytical findings, a design method with robustness consideration is subsequently proposed and draws satisfactory TMDCI designs for both single‐degree‐of‐freedom and multi‐degree‐of‐freedom structures. The designed TMDCI outperforms the comparable devices for both impulsive and seismic response mitigation. The study provides analytical insight into the control capacity of TMDCIs and lays the groundwork for practical design of TMDCIs as an effective and robust control strategy for engineering structures.

A novel design strategy of track‐based asymmetric nonlinear energy sink for seismic response mitigation of structures

Wang,

Zheng

2024

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Mass dampers, whether linear or nonlinear, rely on resonance with the structure to achieve optimal control performance. However, linear mass dampers require frequency tuning, while nonlinear mass dampers are sensitive to input energy levels, rendering both inadequate for control problems that involve frequency and energy uncertainties. To address this issue, the track asymmetric nonlinear energy sink (TANES) has been developed as a robust mass damper against frequency and energy changes. In this study, a novel design strategy consisting of physical and parameter design was proposed for TANESs. First, TANESs with inverted tracks as the auxiliary mass were proposed, resulting in a significant reduction in the dimensions and weight of the device. The new physical design was then realized, and the mathematical descriptions of the TANES system were validated through experiments on a two‐story frame structure. Subsequently, a parameter design method was proposed to match the frequency variation pattern of the TANES with the given structural and load conditions. Following the design procedure, three TANESs with markedly different track shapes were obtained and compared with existing mass dampers under different types of excitations. Results showed that the frequency responses of the TANES systems subjected to harmonic ground excitations shared great similarity with those of a well‐tuned TMD system at small‐to‐moderate energy levels. As the energy level increased, nonlinear responses such as strongly modulated responses were observed in the TANES systems with decrease structural frequencies, which significantly reduced the resonant peak in the frequency responses. The frequency responses of the TANES systems were consistent with the design objective and could be used to quantitatively predict the robustness performance of the devices under impulsive and seismic excitations. With the reduced dimensions and weight resulting from the inverted‐track configuration and the robustness performance in line with common structural and load conditions, the proposed design strategy of TANESs demonstrated great potential in the seismic response mitigation of engineering structures.