Viscoelastic Tuned Mass Damper Research Articles

The optimum enhanced viscoelastic tuned mass dampers: Exact closed-form expressions

This paper introduces the inertial amplifier viscoelastic tuned mass dampers (IAVTMD). The viscoelastic materials are implanted inside the core material of the inertial amplifier tuned mass dampers. The standard linear solid models are applied mathematically to formulate the viscoelastic material. H2 and H ∞ optimization mechanisms apply to derive the exact mathematical closed-form formulations for optimal design parameters for novel inertial amplifier viscoelastic tuned mass dampers. The optimum IAVTMD installs at the top of the structures to mitigate the dynamic responses, determining the dynamic responses analytically through transfer function formation. At first, IAVTMD’s dynamic response reduction capacity compares with the conventional tuned mass damper’s (CTMD) dynamic response reduction capacity. As a result, H2 optimized IAVTMD’s dynamic response reduction capacity is significantly 20.87% and 26.47% superior to two well-established H2 optimized conventional tuned mass damper’s dynamic response reduction capacity. In addition, H ∞ optimized IAVTMD has 15.48% more dynamic response reduction capacity than H ∞ conventional tuned mass damper. H2 and H ∞ optimized tuned mass damper inerters with optimal closed-form solutions are introduced in this paper. A higher damper mass ratio and a lower inerter mass ratio are recommended to produce H2 and H ∞ optimized tuned mass damper inerter (TMDI) with a lower frequency and damping ratio in an affordable range. Accordingly, H2 and H ∞ optimized IAVTMD’s dynamic response reduction capacities are significantly 6.94% and 23.29% superior to H2 and H ∞ optimized TMDI’s dynamic response reduction capacity. The closed-form expressions for optimal design parameters of inertial amplifier viscoelastic tuned mass dampers and tuned mass damper inerters are mathematically correct and effective for practical applications.

Application of Viscoelastic Tuned Mass Dampers in Vibration Mitigation of Steel Joist Jack Arch Floor Structures

A common situation found in many old and modern buildings is the annoying floor vibration. Many old buildings suffer floor vibration as no specific design guidelines were employed to limit the situation. In modern buildings, the development of floors of lighter weight, longer span, and less inherent damping is the main cause for the annoying vibration. In this paper, as a novel application, the influence of viscoelastic tuned mass dampers (TMDs) in vibration mitigation of an existing steel joist jack arch floor structure is investigated using finite element (FE) analysis. Results of a free vibration test conducted on the prototype TMDs are used to validate the FE model. The jack arch floor is subjected to the walking loads of different stepping rates of 1.5, 2, and 3 Hz. Various load models that are available in the literature are used to define the dynamic walking load, and the response mitigation is carried out based on the most critical load models. The influence of design parameters such as the excitation frequency, configuration of the individual dampers in the TMD system, and the mass ratio of the TMD system on the vibration mitigation of the floor structure are investigated in detail. Results of this study indicate that the viscoelastic TMDs are effective in vibration mitigation of jack arch floor structures.

Effect of frequency dependence of large mass ratio viscoelastic tuned mass damper on seismic performance of structures

Abstracts This paper investigates the effect of the frequency dependence of the large mass ratio viscoelastic tuned mass damper (VTMD) on the seismic performance of structures. Compared with conventional TMDs, the frequency dependence of the complex stiffness of VTMD affects its control performance but is always neglected in the seismic analysis of structures. A linear function is introduced to describe the frequency dependence of the real stiffness of the VTMD. An indicator is defined to quantitatively characterize the frequency dependence level of the real stiffness. The effects of the frequency dependence on the control effectiveness and robustness are illustrated by a two degree of freedom (DOF) system under the Gaussian white noise excitation. At last, a numerical simulation of a five-story frame structure under real earthquakes and filtered white noises is presented to illustrate the mitigation effect of the large mass ratio VTMD under different ground conditions. The results show that the frequency dependence level of the VTMD depends on both the type of viscoelastic materials and controlled modal frequency. In the fundamental mode response mitigation, the frequency dependence of the real stiffness improves the control effectiveness and robustness of the VTMD, while in the non-fundamental mode response mitigation, the control effect of the VTMD is weaker to that of the conventional TMD because of the damping characteristic of the complex stiffness element.

A hysteretic absorber to mitigate vibrations of rail noise barriers

Noise barriers for high-speed train lines are subject to strong vibrations due to fluid pressure generated by moving trains. The barriers, generally made of steel cantilever beams, suffer fatigue. For their safety, it is necessary to adopt more resistant solutions or reduce their vibration, as is applied in this study. Following the fundamental work by Den Hartog on viscoelastic tuned mass dampers, later contributions on vibration mitigation have shown a variety of phenomena exhibited by a primary structure connected to a nonlinear light attachment. Vibration reduction of the structure has been observed for selected characteristics of the attachment. Here, the use of a hysteretic absorber is exploited. The device, made of light mass on rubber elements, has the advantage of directly representing the elastic and damping elements. The Bouc-Wen model describes the absorber behavior and its parameters are determined by the experimental results. Due to the dependence of the nonlinear system response on the oscillation amplitude, an optimal tuning is adjusted. The system is calibrated to behave around the 1:1 internal resonance condition. Numerical and experimental results show that the absorber effectively reduces the amplitude and the number of vibration cycles.

Dynamic analysis of viscoelastic tuned mass damper system under harmonic excitation

The purpose of this paper is to investigate the contribution of viscoelastic material (VEM) to the control performance of the viscoelastic tuned mass damper (VTMD). Firstly, the equivalent fractional derivation Kelvin model is used to describe the frequency dependence of viscoelasticity in VTMD, and an index is proposed to characterize the level of frequency dependence. Then the effects of the high loss factor of VEM and frequency dependence of viscoelasticity on the effectiveness and robustness of VTMD control are analyzed by numerical examples. At last, a design strategy for VTMD is proposed to select the type of VEM and optimize its stiffness contribution. The results show that the frequency dependence of shear storage modulus of VEM is beneficial to further reduce the dynamic response of the primary structure equipped with VTMD, and the loss factor of VEM determines the optimum frequency ratio and control effect of VTMD. Compared to the conventional tuned mass damper, VTMD has a better robustness for the positive error of the natural frequency of VTMD but has a worse robustness for the negative error. The frequency dependence of shear storage modulus of VEM is beneficial to the robustness of VTMD for both the positive and negative errors of the natural frequency of the primary structure. The VEM with a strong frequency dependence of shear storage modulus is the ideal VEM for VTMD, and the proposed design strategy can deal with the trade-off between the control effectiveness and control robustness of VTMD.

On the moving load problem in beam structures equipped with tuned mass dampers

This paper proposes an original and efficient approach to the moving load problem on Euler–Bernoulli beams, with Kelvin–Voigt viscoelastic translational supports and rotational joints, and in addition, equipped with Kelvin–Voigt viscoelastic tuned mass dampers (TMDs). While supports are taken as representative of external devices such as grounded dampers or in-span supports with flexibility and damping, the rotational joints may model rotational dampers or connections with flexibility and damping arising from imperfections or damage. The theory of generalised functions is used to treat the discontinuities of the response variables, which involves deriving exact complex eigenvalues and eigenfunctions from a characteristic equation built as determinant of a 4 × 4 matrix. Based on built pertinent orthogonality conditions for the deflection eigenfunctions, a closed-form analytical response is established in the time domain. The proposed solution holds for any number of TMDs and along-axis supports/joints. To show its applicability, accuracy and efficiency, in a numerical application a beam with multiple supports/joints is considered, subjected to a moving concentrated force and a series of concentrated forces, respectively. In two different configurations, the beam is equipped with one TMD and three TMDs, respectively.

Mitigating footfall-induced vibration in long-span floors

Long-span lightweight floor systems with low damping are susceptible to serviceability problems due to human excitations. This paper discusses two remedial measures to alleviate disturbing footfall-induced vibrations observed on a real office floor of steel-concrete composite construction. One treatment involves stiffening the existing floor beams while the other utilises passive control with an innovative distributed multiple viscoelastic tuned mass damper (TMD) system. Several finite element models reflecting different remedial scenarios are analysed from which the TMD approach and the traditional stiffening technique are found to be comparably effective in reducing the vibration level. However, the proposed TMD solution is far superior, feasible and non-intrusive when applied to existing floors. A probability-based evaluation of the effectiveness of the TMD system is also conducted, taking into account likely variations in the walking force and dynamic properties of both the floor and dampers. The custom-made damper system has been successfully installed on the real floor and performed efficiently in various field tests.

Mitigating Footfall-Induced Vibration in Long-Span Floors

Long-span lightweight floor systems with low damping are susceptible to serviceability problems due to human excitations. This paper discusses two remedial measures to alleviate disturbing footfall-induced vibrations observed on a real office floor of steel-concrete composite construction. One treatment involves stiffening the existing floor beams while the other utilises passive control with an innovative distributed multiple viscoelastic tuned mass damper (TMD) system. Several finite element models reflecting different remedial scenarios are analysed from which the TMD approach and the traditional stiffening technique are found to be comparably effective in reducing the vibration level. However, the proposed TMD solution is far superior, feasible and non-intrusive when applied to existing floors. A probability-based evaluation of the effectiveness of the TMD system is also conducted, taking into account likely variations in the walking force and dynamic properties of both the floor and dampers. The custom-made damper system has been successfully installed on the real floor and performed efficiently in various field tests.

Performance of Distributed Multiple Viscoelastic Tuned Mass Dampers for Floor Vibration Applications

Floor vibration due to human activities is becoming a significant concern to designers and developers of long span lightweight floor systems. Modern office floors are now constructed with longer spans and lighter structural members. Actual office dead loads and floor damping are significantly lower than what they were in the past, increasing the potential for annoying floor vibration. Traditional techniques to reduce vibrations through structural modifications have some serious shortcomings, especially with existing structures. This paper discusses the development of an innovative configuration for a tuned mass damper (TMD) using viscoelastic material in rectifying problematic floors. General analytical formulae to predict the response of a floor fitted with multiple identical TMDs are developed. Experimental and numerical studies on the performance of a custom-made distributed multiple viscoelastic TMD system in suppressing the vibration level on an actual office floor subjected to various types of excitations are discussed. The effects of the damper location, the variation in the floor and/or dampers dynamic characteristics on the effectiveness of this control approach have been taken into account. The installed damper system has successfully suppressed the floor response level to an acceptable limit for human comfort, in the case study presented.

Mitigation of Pedestrian-induced Vibrations in Suspension Footbridges via Multiple Tuned Mass Dampers

The dynamic response of suspension footbridges to pedestrian-induced excitations and its passive mitigation, via multiple tuned mass dampers (TMDs), are investigated. First, the nonlinear equations of motion are obtained assuming finite planar motions of the suspension bridge. A suitable approximate version of the equations of motion is shown to be in agreement with existing theories and its linearization is then employed in the structural dynamics analyses. A Galerkin discretization is exploited to calculate both the free and forced dynamic response towards the design of the vibration control system. First, the leading characteristics of the bridge dynamic response are outlined. Resonant vibrations induced by the passage of pedestrians are shown to be effectively reduced using viscoelastic TMDs. As the frequencies of the lowest two modes in suspension footbridges can be very close in the proximity of the crossover phenomenon, three different design scenarios are considered: below, near and above the crossover. In particular, the influence of these scenarios on the passive control architecture is investigated.