Optimum Tuned Mass Damper Parameters Research Articles

Effect of foundation embedment ratio in suppressing seismic-induced vibrations using optimum tuned mass damper

Tuned mass damper (TMD), which is used in structures to mitigate the dynamic responses caused by environmental loads, is tuned according to the dominant frequency of the structures. The dominant frequency of structure built on soil with low stiffness is significantly affected by the soil-structure interaction (SSI). In previous studies, only the surface foundation case is considered to investigate the design parameters of TMD considering SSI effects and the embedment depth of the foundation is neglected in these studies. Thus, this paper investigates the optimization of TMD for mitigation of responses of a high-rise building considering various depths of embedment and soil properties. The optimum parameters of TMD are investigated using five different optimization algorithms (i.e., simulated annealing, sequential quadratic programming, genetic algorithm, pattern search, and particle swarm optimization). The objective function minimizes the peak acceleration amplitude at the top of the structure. The effectiveness of optimum TMD is verified to use 20 near-fault pulse-like ground motions. The comparisons show that the embedment ratio of the foundation and the soil properties significantly affect the optimization of TMD.

Closed-Form Derivation of Optimum Tuned Mass Damper Parameter Based on Modal Multiplicity Criteria

It is presently established that properly designed tuned mass dampers (TMD) systems can effectively control the vibrations induced due to the wind and/or the seismicity. The TMD is one of the most used passive control systems in high-rise structural systems in an era of recent developments. The optimum parameters for the damped system to date require a numerical search technique or shootout technique, which is the trial-error method, of-course add complexity in selecting parameters obtained at optimality conditions. The study of optimum parameters based on modal multiplicity criteria showcases the complete closed-form solution, independent to another optimum parameter. The parameters presented in this study solely depend on structural damping and mass ratio. The derived optimum parameters are compared with the existing parameters in this field. This study also investigates parametric uncertainty for structural configuration under the harmonic excitation. To confirm its robustness under random vibration, various earthquake time history loads are applied to study the effect of structural displacement and acceleration response. In the end, the energy concept is deployed to explain how effectively the optimum TMD parameters help to reduce the kinetic energy, damping energy, strain energy, and input energy.

Performance enhancement of a tuned mass damper for vibration suppression of an offshore jacket platform utilizing a novel metaheuristic optimization technique

Offshore platforms are key structures in energy provision that are subjected to continuous and harsh environmental loadings. A tuned mass damper (TMD) has been proposed as a robust and effective vibration control method for marine structures. However, selecting optimum TMD parameters under certain constraints may become a multimodal optimization problem. Several studies focused on finding the TMD optimum parameters using different metaheuristic optimization algorithms. Nonetheless, it becomes a necessity to find an answer to the question: which algorithm can find the most effective TMD parameters to minimize the structure response? This paper presents the use of a novel metaheuristic optimizer, the Improved Grey Wolf Optimizer (IGWO), for optimum tuning of a TMD aimed at reducing the wave-induced vibration level of a jacket type platform. Moreover, a comprehensive performance analysis of four different metaheuristic algorithms for optimizing a TMD has been investigated. They are IGWO, popular algorithms such as Genetic Algorithm (GA), Particle Swarm Optimization (PSO), and Whale Optimization Algorithm (WOA). In order to achieve this purpose, a finite element (FE) model representing a prototype of a jacket-type platform under the influence of irregular waves is numerically solved in COMSOL Multiphysics. Irregular waves are presented using the JONSWAP spectrum and hydrodynamic forces are modeled using Morison's equation. The comparative algorithms are evaluated for the independent minimization of three different objective functions. The target parameters of TMD to be tuned are the mass ratio (μ), the frequency ratio (fopt), and the damping ratio (ζopt). Finally, the optimized TMD will be applied to the FE model and the resultant response will be investigated. The results demonstrate the superior ability of the IGWO optimizer to optimally tune a TMD attached to marine structures compared with the other algorithms. In addition, IGWO proved its unique ability to steadily converge toward the global minimum value.

Optimal Design of Tuned Mass Damper for Base-Excited Structures

The tuned mass damper (TMD) is a well-established vibration control device that has been implemented in several structures worldwide. The performance of passive TMD is greatly dependent on its design parameters. A key issue for the design of the optimal TMD is the identification of the parameters of the structure to which the TMD is to be attached. Here, it is important also to consider the perturbations that may arise in the structural frequency due to different practical issues. The present work focusses on this and aims to obtain the optimum TMD parameters in a Genetic Algorithm (GA) framework. The results of the proposed optimal strategy, in terms of optimal tuning ratio and optimal damping ratio, for a given value of the mass ratio, are compared with some of the existing optimal solutions for linear TMD under base excitation. The effectiveness of all these optimally designed TMDs in reducing the structural response is further demonstrated when the structure-TMD system is subjected to recorded earthquake ground motions. It is seen that in the tuned condition, the control performance obtained by the different designs of the TMD are similar to each other, although having some minor differences in the values of the optimum parameters. Also, the effectiveness of the different TMD designs in the detuned condition is investigated, in which the present design technique is found to be the most effective.

NUMERICAL MODELLING OF MULTIPLE TUNED MASS DAMPER EQUIPPED WITH MAGNETO RHEOLOGICAL DAMPER FOR ATTENUATION OF BUILDING SEISMIC RESPONSES

The Tuned Mass Damper (TMD) is generally as a passive vibration control device consisting of added auxiliary mass with functioning spring and damping elements. TMD is basically designed to be tuned to the dominant frequency of a structure which the excitation of frequency will resonate the structural motion out of phase to reduce unwanted vibration. However, a single unit TMD is only capable of suppressing the fundamental structural mode. In order to control multimode vibrations and to cater wide band seismic frequency, more than one TMD is required to improve the effectiveness of a control mechanism. For the purpose of this study, a 3-storey benchmark reinforced structural building subjected to El Centro seismic ground motion is modelled as uncontrolled Primary Structure (PS) by considering appropriate structural properties such as stiffness and damping. Mathematical modelling of uncontrolled PS is developed and further evaluated numerically by assuming the PS as an equivalent lumped system. For the case of controlled PS which the passive mechanism is included to the system, optimum parameters of both TMD and Multiple TMD (MTMD) are designed to be tuned to the dedicated structural modes where the performance is dependent on specified parameters such as auxiliary mass ratio, optimum damping ratio, and optimum frequency ratio. The eigen value analysis is carried out by assuming that the structure is a linear time-invariant system. The input and output components of structural system arrangements are then characterized in the transfer function manner and then converted into state space function. To enhance structural control effectiveness, the adaptive system is incorporated by the attachment of Magneto-Rheological (MR) damper to both single TMD and MTMD passive system. The response analysis of the control system arrangements is executed using both time history and frequency response analysis. The main objectives of the design are to minimize both structural peak and Root Mean Square (RMS) displacements. From the analysis, the designed control mechanisms are concluded as highly effective in reducing all structural floor displacements for the semi-active cases with 99% displacement reduction for the third and second floors, and 98% for the first floor, compared to the uncontrolled case. It is concluded that the MR damper significantly contributed to the enhancement of the passive system to mitigate structural seismic vibration.

Estimation of optimum tuned mass damper parameters via machine learning

The performance of tuned mass dampers (TMDs) relies on a tuning process in which the parameters are optimized for one or several objectives. For this purpose, several formulations and numerical optimization methods have been developed. The existing closed form formulation may not be suitable for a desired objective, and numerical optimization methods must be applied to every different system. For that reason, optimum TMD parameters such as period and damping ratio can be estimated by using machine learning. Since the use of machine learning in TMD optimization is a novel field of research, a well-known Artificial Neural Network (ANN) model is proposed. Training of the ANN was done by using optimum TMD values of several sets of single degree of freedom (SDOF) structures. The optimum values were found according to an optimization process using a flower pollination algorithm (FPA) and transfer function amplitude as an objective in the frequency domain. The generated ANN model is generally effective to find the same optimum results as the FPA approach up to two decimal places. Also, the ANN model was used to generate three basic tuning formulations, which are tested on SDOF and multiple degrees of freedom (MDOF) structural models. Including the responses under seismic excitation by considering stroke of the TMD, the optimum TMD parameters defined according to the developed formulations are more effective than optimum results found by existing formulations for reduction of maximum structural responses.

Optimum Parameters for Large Mass Ratio TMDs Using Frequency Response Function

ABSTRACT The paper proposes a new approach for optimal design structures equipped with tuned mass dampers (TMDs) with large mass ratios. The approach is based on minimizing the frequency response function (FRF) of displacement response of the structure as well as the acceleration of the TMD that leads to almost equal modal damping ratios in the first and second mode of vibration. Furthermore, two regression equations are proposed to predict the optimum TMD properties. It is concluded that choosing the optimum TMD parameters as suggested in this study provides up to 94% reduction in the maximum FRF of structural displacement.

Study on TMD Control on Stability Improvement of Barge-Supported Floating Offshore Wind Turbine Based on the Multi-Island Genetic Algorithm

A floating offshore wind turbine (FOWT) has a great potential in producing renewable energy as offshore wind resource is rich in deep sea area (water deeper than 60 m) where fixed foundations are cost-effective or deployable. However, compared with a fixed-bottom installation, FOWT has to suffer more extreme loads due to its extra degrees of freedom. Therefore, the stability of an FOWT is a key challenge in exploiting offshore deep-water wind. Focusing on the stability of barge-type FOWT, this paper is to investigate the effect of passive structural control by equipping a tuned mass damper (TMD) on the nacelle. The turbulent wind with sharp fluctuations is established both in velocity and inflow direction based on standard Kaimal turbulence spectrum as suggested in the standard IEC61400-2. The irregular wave is generated according to the Pierson-Moskowitz spectrum. The dynamic structural characteristics of FOWT are calculated based on the fully coupled aero-hydro-servo-elastic solver FAST. Evidence has shown that the proposed method of the nacelle-based TMD is effective in controlling stability of an FOWT, as the sway and roll motions of barge and the side-side displacement of tower top decreased significantly. With the increase of mass, the side-side displacement of tower-top and the amplitude of roll motion of barge reveal a trend of increasing first and then decreasing. The stiffness and damping have little effect. Furthermore, the multi-island genetic optimization algorithm (MIGA) is employed to find globally optimum structural parameters (mass, stiffness and damping) of the TMD. The optimum structure parameters of TMD are achieved when the mass is 21393 kg, damping is 13635 N/(m/s) and stiffness is 6828 N/m. By adopting the optimized TMD, stability of roll motion of barge and side-side displacement of tower-top increase up to 53% and 50% respectively when compared with the normal TMD. The simulation results verify the validity and reliability of the proposed TMD control and the optimization methods.

Preliminary study on tuned mass damper utilization to reduce wave-induced vibration of jacket platforms

PurposeDuring its operation, vibrations in jacket platform due to high operational and environmental loads could reduce its productivity and endanger its safety. Tuned mass damper (TMD) is one of the vibration control devices commonly used in buildings to reduce their response. Basically, TMD is a device attached to a structure as a mass on properly tuned spring and damping elements. The purpose of this paper is to study the utilization of TMD to reduce the wave-induced vibration of platforms.Design/methodology/approachFirst, the study investigates the optimum TMD parameters to reduce the response of the platform. The effectiveness of the optimized TMD in reducing platform response due to wave load is then analyzed. Finally, the reduced response of the platform is attributed to an extension of platform service life. Cyclic load in the form of vibration is related to cyclic stress on the tubular connections on a jacket platform, which causes fatigue failure. Fatigue performance of a platform is quantified by its fatigue life, which should be at least twice the intended service life.FindingsIt is found that the optimized TMD cannot be achieved by simply adjusting the TMD damping as high as possible. The results show that the response of controlled platforms by properly tuned TMD could be reduced by about 20 percent from the uncontrolled case.Originality/valueAlthough vibration of a structure can be reduced by increasing its stiffness, this approach is considered not economical since it increases the cost for material construction. With the falling of oil prices, an optimization of jacket platform structure is considered necessary to reduce its construction cost. TMD can be used as an alternate solution, even though the only recorded utilization of TMD on a jacket platform is known in Sakhalin Platform in Russia. This fact gives a motivation to carry out more studies about TMD application on jacket platform, as this device is already used in numerous of inland structures.

Tranfer function amplitude minimization for structures with tuned mass dampers considering soil-structure interaction

The optimum tuned mass damper (TMD) parameters rely on the superstructure's natural frequency, which, in turn, depends on the soil condition under the structure. Thus, the consideration of soil conditions in determination of the optimum TMD parameters is necessary.In this study, a methodology is proposed for the determination of TMD parameters considering soil-structure interaction. The objective function in the study is the acceleration transfer function. For the stochastic optimization problem, several metaheuristic algorithms, namely harmony search, flower pollination algorithm, teaching, learning based optimization, Jaya algorithm and two new versions of it are employed. Numerical experiments on methodology are presented for a 40-story structure considering soil-structure interaction.It is shown through applications that, especially for soft soils, the use of TMDs is an effective way to damp structural vibrations resulting from seismic sources and consideration of the base stiffness is effective on the optimum TMD parameters. Comparisons among the results obtained through different metaheuristic algorithms are also given.

Cuckoo Search-Based Least Squares Support Vector Machine Models for Optimum Tuning of Tuned Mass Dampers

Tuned mass dampers (TMDs) have been widely used to suppress or absorb vibration. Optimum tuning of the TMD parameters using metaheuristic algorithms demands numerous numerical analyses which is a tedious and time-consuming task. Recent advances in data processing systems have attracted great attention towards the creation of intelligent systems to evolve models in engineering applications. The present paper implements the least squares support vector machine (LS-SVM) to build up models which predict the optimum TMD parameters. The performance of the proposed models is largely dependent on the quantity and the accuracy of databases used for training the models. Therefore, a wide-range numerical tuning of the TMD system, attached to a single-degree-of freedom (SDOF) main system, is done using a novel metaheuristic algorithm, called the cuckoo search (CS), to obtain the tuning frequency and damping ratio of the TMD system for a main system subjected to three types of excitations: external white-noise force, harmonic base acceleration and white-noise base acceleration. The superior performance of the LS-SVM models in prediction of optimum TMD parameters is proved in comparison to other studies in the literature. Furthermore, it is found that the optimum TMD parameters are not influenced by the predominant frequency of the filtered white-noise excitation.

Application of an Artificial Fish Swarm Algorithm in an Optimum Tuned Mass Damper Design for a Pedestrian Bridge

Tuned mass damper (TMD) has a wide application in the human-induced vibration control of pedestrian bridges and its parameters have great influence on the control effects, hence it should be well designed. A new optimization method for a TMD system is proposed in this paper, based on the artificial fish swarm algorithm (AFSA), and the primary structural damping is taken into consideration. The optimization goal is to minimize the maximum dynamic amplification factor of the primary structure under external harmonic excitations. As a result, the optimized TMD has a smaller maximum dynamic amplification factor and better robustness. The optimum TMD parameters for a damped primary structure with different damping ratios and different TMD mass ratios are summarized in a table for simple, practical design, and the fitting equation is also provided. The TMD configuration optimized by the proposed method was shown to be superior to that optimized by other classical optimization methods. Finally, the application of an optimized TMD based on AFSA for a pedestrian bridge is proposed as a case study. The results show that the TMD designed based on AFSA has a smaller maximum dynamic amplification factor than the TMD designed based on the classic Den Hartog method and the TMD designed based on the Ioi Toshihiro method, and the optimized TMD has a good effect in controlling human-induced vibrations at different frequencies.

Tuning of mass dampers for preventing brittle fracture by employing teaching learning based optimization

AbstractIn design of reinforced concrete structures, a ductile design is needed, because the brittle fracture is sudden. Also, the energy absorbed by the structure is effective for ductile structures during earthquake excitations. In design regulations, especially for vertical supporters such as columns, the shear force and axial force capacity is limited, although the strength of the members is not at the limits. For that reason, the shear forces of structures excited by earthquakes can be reduced by adding a tuned mass damper (TMD), but TMD must be optimized and it must not be heavy. If the mass of the TMD is not optimized, the ductile behaviour constraint about the axial force capacity cannot be provided. The compressive strength of the concrete is a measure for the effective application of a TMD to a reinforced concrete structure. Since the mass is limited by the design constraint, the other design variables of TMD such as period and damping ratio are optimized. Using the formulas for frequency and damping ratio related to a preselected mass may not be sufficient and a precise optimum solution for preventing brittle fracture. Metaheuristic methods can be used by using a specific limit. In this study, Teaching Learning Based Optimization (TLBO) is employed to find optimum TMD parameters. Several earthquake excitations were used in the optimization process. A three storey RC frame structures with different compressive strength of concrete is investigated. Three stopping criteria have been used in the proposed methodology. The first criterion is the reduction of the maxi‐mum shear force value for the most critical excitation to the ductile behaviour limit. The second criterion is the reduction of the ratio of maximum first storey displacements of structure with and without TMD. This value is reduced under a user defined value, but the user defined value can be entered as zero. This value can be iteratively increased for minimization. The last criterion is the reduction of the acceleration transfer function of the structure. The proposed method is feasible on finding optimum TMD ensuring ductility conditions. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Closed-form optimum tuning formulas for passive Tuned Mass Dampers under benchmark excitations

This study concerns the derivation of optimum tuning formulas for a passive Tuned Mass Damper (TMD) device, for the case of benchmark ideal excitations acting on a single-degree-of-freedom (SDOF) damped primary structure. The free TMD parameters are tuned first through a non-linear gradient-based optimisation algorithm, for the case of harmonic or white noise excitations, acting either as force on the SDOF primary structure or as base acceleration. The achieved optimum TMD parameters are successively interpolated according to appropriate analytical fitting proposals, by non-linear least squares, in order to produce simple and effective TMD tuning formulas. In particular, two fitting models are presented. The main proposal is composed of a simple polynomial relationship, refined within the fitting process, and constitutes the optimum choice. A second model refers to proper modifications of literature formulas for the case of an undamped primary structure. The results in terms of final (interpolated) optimum TMD parameters and of device effectiveness in reducing the structural dynamic response are finally displayed and discussed in detail, showing the wide and ready-to-use validity of the proposed optimisation procedure and achieved tuning formulas. Several post-tuning trials have been carried out as well on SDOF and MDOF shear-type frame buildings, by confirming the effective benefit provided by the proposed optimum TMD.

New approaches in reliability based optimization of tuned mass damper in presence of uncertain bounded parameters

This work deals with control of vibrating structures using tuned mass damper (TMD) in presence of uncertain bounded structural parameters. The adopted optimization strategy of the TMD parameters is the reliability based optimization (RBO) where the failure probability, approximated with the classical Rice’s formula, is related to the primary structure displacement. In presence of uncertain bounded structural parameters it is convenient to describe them using intervals. Consequently, the optimized failure probability is also defined over an interval.In this paper a continuous-optimization nested loop method (CONLM) is presented to provide the exact range of the optimum TMD parameters and their corresponding failure probabilities. The CONLM is time consuming; in this context an approximation method using the monotonicity-based extension method (MBEM) with box splitting is also proposed. Therefore, the initial non-deterministic optimization problem can be transformed into two independent deterministic sub-problems involving discrete-optimization nested loop rather than the continuous-optimization nested loop used in the CONLM. The effectiveness and robustness of the presented optimum bounds of the TMD parameters are investigated and a performance index is introduced. The numerical results obtained with a one degree of freedom and a multi-degree of freedom systems subject to different seismic motions have shown the efficiency of the proposed methods, even with high level of uncertainties. Besides, the good robustness of the TMD device when it is exactly tuned on the optimum TMD parameters corresponding to the deterministic structural parameters has been proven.

Optimum Parameters for Tuned Mass Damper Using Shuffled Complex Evolution (SCE) Algorithm

This study is investigated the optimum parameters for a tuned mass damper (TMD) under the seismic excitation. Shuffled complex evolution (SCE) is a meta-heuristic optimization method which is used to find the optimum damping and tuning frequency ratio for a TMD. The efficiency of the TMD is evaluated by decreasing the structural displacement dynamic magnification factor (DDMF) and acceleration dynamic magnification factor (ADMF) for a specific vibration mode of the structure. The optimum TMD parameters and the corresponding optimized DDMF and ADMF are achieved for two control levels (displacement control and acceleration control), different structural damping ratio and mass ratio of the TMD system. The optimum TMD parameters are checked for a 10-storey building under earthquake excitations. The maximum storey displacement and acceleration obtained by SCE method are compared with the results of other existing approaches. The results show that the peak building response decreased with decreases of about 20% for displacement and 30% for acceleration of the top floor. To show the efficiency of the adopted algorithm (SCE), a comparison is also made between SCE and other meta-heuristic optimization methods such as genetic algorithm (GA), particle swarm optimization (PSO) method and harmony search (HS) algorithm in terms of success rate and computational processing time. The results show that the proposed algorithm outperforms other meta-heuristic optimization methods.

Optimum tuned mass damper approaches for adjacent structures

Pounding of adjacent structures are always a notable reason for damages after strong ground motions, but it is already unforeseen detail in newly constructed structures. Thus, several approaches have been proposed in order to prevent the pounding of structures. By using optimally tuned mass dampers, it is possible to decrease the displacement vibrations of structures. But in adjacent structures, the response of both structures must be considered in the objective function of optimization process. In this paper, two different designs of Tuned Mass Dampers (TMD) are investigated. The first design covers independent TMDs on both structures. In the second design, adjacent structures are coupled by a TMD on the top of the structures. Optimum TMD parameters are found by using the developed optimization methodology employing harmony search algorithm. The proposed method is presented with single degree of freedom and multiple degree of freedom structures. Results show that the coupled design is not effective on multiple degree of freedom adjacent structures. The coupled design is only effective for rigid structures with a single degree of freedom while the use of independent TMDs are effective on both rigid and flexural structures.

Tuned Mass Damper optimization for the mitigation of human-induced vibrations of pedestrian bridges

The design of Tuned Mass Dampers (TMD) to satisfy serviceability requirements is becoming more and more usual in the current design of footbridges. This paper analyzes the TMD design for the mitigation of pedestrian-induced vibrations with three main objectives: the introduction of a specific TMD optimization criterion for pedestrian-induced vibrations of footbridges, a critical analysis of the applicability to this specific loading scenario of classic literature optimization criteria, and a quantification of the TMD efficiency in the reduction of the footbridge acceleration. A numerical optimization criterion is proposed, based on the maximization of an efficiency factor, defined as the ratio between the uncontrolled acceleration standard deviation and the controlled one. Optimum TMD parameters are compared with classic criteria given by the literature. A possible modification of TMD parameters that permits to keep the TMD relative displacement within prescribed limits (aspect that is often a technical requirement in the TMD design) is also discussed. Monte Carlo simulations are carried out in order to confirm the validity of the standard deviation-based optimization for the reduction of the maximum dynamic response of the bridge. An application to a real footbridge is finally presented.

Optimum tuned mass damper design for preventing brittle fracture of RC buildings

Brittle fracture of structures excited by earthquakes can be prevented by adding a tuned mass damper (TMD). This TMD must be optimum and suitable to the physical conditions of the structure. Compressive strength of concrete is an important factor for brittle fracture. The application of a TMD to structures with low compressive strength of concrete may not be possible if the weight of the TMD is too much. A heavy TMD is dangerous for these structures because of insufficient axial force capacity of structure. For the preventing brittle fracture, the damping ratio of the TMD must be sufficient to reduce maximum shear forces below the values proposed in design regulations. Using the formulas for frequency and damping ratio related to a preselected mass, this objective can be only achieved by increasing the mass of the TMD. By using a metaheuristic method, the optimum parameters can be searched in a specific limit. In this study, Harmony Search (HS) is employed to find optimum TMD parameters for preventing brittle fracture by reducing shear force in additional to other time and frequency responses. The proposed method is feasible for the retrofit of weak structures with insufficient compressive strength of concrete.

Parameter optimization and structural design of tuned mass damper for shanghai centre tower

AbstractWith a height of 632 m, Shanghai centre tower (SHC), located in Lujiazui district of Shanghai, will be the highest building in China. A tuned mass damper (TMD) system will be set in the upper part to control the structural wind‐induced response. The optimum control parameters of TMD were obtained through different optimization cases of TMD system parameters for wind vibration control. Then, Based on the conceptual design of SHC TMD system, theoretical analysis and formula derivation of dual pendulum systems, which is an improved form of traditional pendulum systems, was carried out, and the fundamental design method and process of dual pendulum systems is proposed in the paper. Copyright © 2010 John Wiley & Sons, Ltd.