Design Of Tuned Mass Dampers Research Articles

Dynamic response and optimal design of structures with large mass ratio TMD

AbstractThis paper investigates the dynamic behavior and the seismic effectiveness of a non‐conventional Tuned Mass Damper (TMD) with large mass ratio. Compared with conventional TMD, the device mass is increased up to be comparable with the mass of the structure to be protected, aiming at a better control performance. In order to avoid the introduction of an excessive additional weight, masses already present on the structure are converted into tuned masses, retaining structural or architectural functions beyond the mere control function. A reduced order model is introduced for design purposes and the optimal design of a large mass ratio TMD for seismic applications is then formulated. The design method is specifically developed to implement High‐Damping Rubber Bearings (HDRB) to connect the device mass to the main structure, taking advantage of combining stiffness and noticeable damping characteristics. Ground acceleration is modeled as a Gaussian random process with white noise power spectral density. A numerical searching technique is used to obtain the optimal design parameter, the frequency ratio alpha, which minimizes the root‐mean‐square displacement response of the main structure. The study finally comprises shaking table tests on a 1:5 scale model under a wide selection of accelerograms, both artificial and natural, to assess the seismic effectiveness of the proposed large mass ratio TMD. Copyright © 2011 John Wiley & Sons, Ltd.

A comparison between different optimization criteria for tuned mass dampers design

Tuned mass sampers (TMDs) are widely used strategies for vibration control in many engineering applications, so that many TMD optimization criteria have been proposed till now. However, they normally consider only TMD stiffness and damping as design variables and assume that the tuned mass is a pre-selected value. In this work a more complete approach is proposed and then also TMD mass ratio is optimized. A standard single degree of freedom system is investigated to evaluate TMD protection efficiency in case of excitation at the support. More precisely, this model is used to develop two different optimizations criteria which minimize the main system displacement or the inertial acceleration. Different environmental conditions described by various characterizations of the input, here modelled by a stationary filtered stochastic process, are considered. Results show that all solutions obtained considering also the mass of the TMD as design variable are more efficient if compared with those obtained without it. However, in many cases these solutions are inappropriate because the optimal TMD mass is greater than real admissible values in practical technical applications for civil and mechanical engineering. Anyway, one can deduce that there are some interesting indications for applications in some actual contexts. In fact, the results show that there are some ranges of environmental parameters ranges where results attained by the displacement criterion are compatible with real applications requiring some percent of main system mass. Finally, the present research gives promising indications for complete TMD optimization application in emerging technical contexts, as micromechanical devices and nano resonant beams.

Fuzzy-entropy based robust optimization criteria for tuned mass dampers

Tuned mass dampers (TMD) are well known as one of the most widely adopted devices in vibration control passive strategies. In the past few decades, many methods have been developed to find the optimal parameters of a TMD installed on a structure and subjected to a random base excitation process, but most of them are usually based on an implicit assumption that all of the structural parameters are deterministic. However, in many real cases this simplification is unacceptable, so robust optimal design criteria becomes a viable alternative to better support engineers in the design process. In Robust Design Optimization (RDO) approaches, indeed the solution must be able to not only minimize the performance but also to limit its variation induced by uncertainty. Most of the currently available RDO methods are based on a probabilistic description of the model uncertainty, even if in many cases they are not able to explicitly include the influence of all the possible sources of uncertainties. Therefore, in this study, a fuzzy version of the robust TMD design optimization problem is proposed. The consistency of the fuzzy approach is studied with respect to the available non-probabilistic formulations reported in the literature and an application to an example of a robust design of a linear TMD subjected to base random vibrations in the presence of fuzzy uncertainties. The results show that the proposed fuzzy-based approach is able to give a set of optimal solutions both in terms of structural efficiency and sensitivity to mechanical and environmental uncertainties.

Design and implementation of nonlinear TMD for chatter suppression: An application in turning processes

A new-type nonlinear tuned mass damper (TMD) containing an additional element of elastic support dry friction compared with the common linear TMD is proposed to suppress machining chatter. The design and tuning process of this nonlinear TMD have used a combination of analytical modeling with experimentally measured frequency response function (FRF) of the machining system. Theoretical studies and experimental results show that the proposed nonlinear TMD can remarkably improve the machining stability by effectively suppressing the magnitude of the real part of the FRF of the damped machining system.

Reliability based multiobjective optimization for design of structures subject to random vibrations

Based on a multiobjective approach whose objective function (OF) vector collects stochastic reliability performance and structural cost indices, a structural optimization criterion for mechanical systems subject to random vibrations is presented for supporting engineer’s design. This criterion differs from the most commonly used conventional optimum design criterion for random vibrating structure, which is based on minimizing displacement or acceleration variance of main structure responses, without considering explicitly required performances against failure. The proposed criterion can properly take into account the design-reliability required performances, and it becomes a more efficient support for structural engineering decision making. The multiobjective optimum (MOO) design of a tuned mass damper (TMD) has been developed in a typical seismic design problem, to control structural vibration induced on a multi-storey building structure excited by nonstationary base acceleration random process. A numerical example for a three-storey building is developed and a sensitivity analysis is carried out. The results are shown in a useful manner for TMD design decision support.

Robust design of mass-uncertain rolling-pendulum TMDs for the seismic protection of buildings

Commonly used for mitigating wind- and traffic-induced vibrations in flexible structures, passive tuned mass dampers (TMDs) are rarely applied to the seismic control of buildings, their effectiveness to impulsive loads being conditional upon adoption of large mass ratios. Instead of recurring to cumbersome metal or concrete devices, this paper suggests meeting that condition by turning into TMDs non-structural masses sometimes available atop buildings. An innovative roof-garden TMD, for instance, sounds a promising tool capable of combining environmental and structural protection in one device. Unfortunately, the amount of these masses being generally variable, the resulting mass-uncertain TMD (MUTMD) appears prone to mistuning and control loss. In an attempt to minimize such adverse effects, robust analysis and synthesis against mass variations are applied in this study to MUTMDs of the rolling-pendulum type, a configuration characterized by mass-independent natural period. Through simulations under harmonic and recorded ground motions of increasing intensity, the performance of circular and cycloidal rolling-pendulum MUTMDs is evaluated on an SDOF structure in order to illustrate their respective advantages as well as the drawbacks inherent in their non-linear behavior. A possible implementation of a roof-garden TMD on a real building structure is described and its control efficacy numerically demonstrated, showing that in practical applications MUTMDs can become a good alternative to traditional TMDs.

Timoshenko Beam with Tuned Mass Dampers to Moving Loads

The structural analysis of a Timoshenko beam system with tuned mass dampers (TMDs) under moving-load excitation is presented. A proposed simplified two-degrees-of freedom system based on the first mode of the Timoshenko beam is employed for the design of TMDs. The dynamic characteristics of a Timoshenko beam, such as the structural-resonant and phase-resonant velocities, and the effectiveness of a TMD for vibrational control are especially emphasized. A practical example of an elevated railway subjected to the Japanese Shinkansen (SKS) high-speed bullet train is included.

Efficacy of Tuned Mass Dampers for Bridge Flutter Control

This paper examines efficacy of tuned mass dampers (TMD) in controlling self-excited motion resulting from negative damping. New optimal TMD parameters are suggested which provide better performance than those suggested in the literature. The dependence of TMD performance on structural damping is highlighted. The equations of motion of a combined system comprised of multiple TMDs attached to a bridge deck are presented where the bridge motion is described in terms of reduced-order modal coordinates. Details concerning the multimode coupled flutter of long-span bridges with auxiliary TMDs are provided. The effectiveness and limitations of TMDs for controlling multimode bridge flutter are examined, emphasizing the dependence of TMD performance on the bridge dynamic and aerodynamic characteristics. This study shows that the effectiveness of TMDs is rather limited in controlling a hard-type flutter characterized by negative aerodynamic damping that grows rapidly with increasing wind speed beyond the onset of flutter. However, it is relatively effective in controlling a soft-type flutter in which the negative damping builds up slowly with increasing wind speed. Robust TMD design issues are also discussed in light of their sensitivity to design parameters in the vicinity of optimal values.

Tuned Mass Damper Design for Optimally Minimizing Fatigue Damage

Traditionally the usage of a tuned mass damper (TMD) is to improve the survivability of the primary structure under an extraordinary loading environment while the design loading condition is often described by a harmonic function, or sometimes by a stationary random process that can be fully characterized by a power spectral density (PSD) function. In contrast, this paper considers the environmental loading to be a long-term nonstationary stochastic process characterized by a probabilistic PSD function. One engineering motivation to design a TMD under a long-term random loading condition is for prolonging the fatigue life of the primary structure. The primary contribution of this study is to provide the theoretical framework for designing a TMD that can optimally minimize structural fatigue damage.

Parametric study and simplified design of tuned mass dampers

This paper summarizes the results of a parametric study performed to enhance the understanding of some important characteristics of tuned mass dampers (TMD). The effect of detuning on some of the TMD parameters on the performance is studied using steady-state harmonic excitation analysis and time-history analysis. The El Centro and Mexico excitations are used for time-history analysis. The effects of tuning criteria and significance of numerical tuning are also studied. The correspondence between the design of a TMD for a SDOF structure and a certain mode of a MDOF structure is drawn to simplify TMD design to control a single mode of a multimodal structure. An example is given to illustrate the design procedure. Investigations are made regarding controlling multiple structural modes using multi-tuned mass dampers (MTMD).

Effects of structural uncertainties on TMD design: A reliability‐based approach

AbstractThis study investigates the effects of structural uncertainties on the design and performance evaluation of passive tuned mass dampers (TMD) used for vibration control. A probabilistic optimal design methodology is presented in which time‐invariant uncertain structural parameters are modelled by random variables with prescribed probability distribution. Unlike conventional TMD designs based on minimizing the mean‐square response, a reliability‐based performance index is considered in the proposed design which properly accounts for uncertainties in load and structural models. An approximate asymptotic expansion is used to compute the multidimensional reliability integrals arising in the proposed optimal design methodology. Accuracy and effectiveness issues are addressed by comparing results obtained using this approximation with corresponding results obtained by numerical integration. The importance of structural uncertainties is demonstrated by applying the methodology to a single degree of freedom structure subjected to broadband excitations that are modelled by stationary white noise. It is found that the consideration of structural uncertainties improves substantially the robustness of the TMD design. Also, the reliability‐based TMD‐design methodology results into significantly larger structural reliability compared to that obtained by the conventional design approach based on minimizing the mean‐square response.

Verification of the effectiveness of TMDs using wind tunnel section model tests

Abstract Wind tunnel tests for the Hoga Kusten Bridge, now under construction in Sweden, have suggested that the bridge will experience large torsional motions for the particular case of snow accumulated in the railings. The designers of the bridge proposed the use of tuned mass dampers (TMDs) to reduce these motions, thus ensuring the safety of the bridge for wind speeds above approximately 40 m/s. The effectiveness of the TMDs was tested in a wind tunnel at the Danish Maritime Institute (DMI) through section model tests, with the aim of optimizing the TMD design. Tests have shown the TMDs to be highly effective, reducing the RMS torsional motions of the deck by a factor of almost 10. Tests varying many parameters of the TMD design were conducted to optimize the TMD design; the greatest improvement in bridge deck performance was achieved by increasing the TMD mass moment of inertia ratio either by increasing the distance from the TMDs to the bridge centreline or by increasing the moving mass of the TMD.

A practical method of passive TMD for suppressing wind-induced vertical buffeting of long-span cable-stayed bridges and its application

Formulas for the reduction ratio of tuned mass dampers (TMD) for suppressing the wind-induced vertical buffeting response of long span bridges and the optimal solutions of the parameters of TMD for engineering purposes are derived. The accuracy of the formulas relevant to the design of TMD is confirmed. An aeroelastic test of a full model of the Yangpu Bridge with and without TMD was done, and it was found that the results for the reduction ratio obtained from the test were in good agreement with those from the formulae. Some meaningful results are obtained from the detailed analysis. In addition, “TMD design wind speed” and the constraint conditions are further stressed and discussed. Finally, the Yangpu Bridge is taken as an example to show the application of these formulae.

Control of wind-induced vibrations in civil engineering structures

Various passive-type control means for wind-induced vibrations of civil engineering structures (mainly bridges) are reviewed. Control means discussed primarily are, Aerodynamic means·Tuned mass dampers (TMD) including Tuned liquid dampers (TLD) and·Non-tuning type dampersApplication of such means to actual structures are also presented. Effectiveness and design of TMD to wind-induced self-excited vibration are discussed in some detail.