Optimum tuning of Tuned Mass Dampers for frame structures under earthquake excitation (original) (raw)
Related papers
2014
The mitigation of the dynamic response of buildings and structures to earthquakes is one of the fundamental aims within the design of vibration control devices. In this sense, Tuned Mass Damper (TMD) devices are generally conceived as useful and efficient means for the control of the dynamic response of structures and constructions, especially when considering ideal dynamic excitations. However, their optimum tuning and relevant performance in effectively reducing the seismic response of civil structures is currently an open topic, mostly due to the intrinsic nature of the (passive) device and the uncertainty and unpredictability of the earthquake event. The present paper deals with the concept of optimisation of the TMD at given seismic input, to assess the optimum TMD parameters for each seismic event. In this study, the optimisation of TMDs is firstly carried out within a range of earthquakes and primary frame structures, in order to achieve the ideal optimum setting for each con...
Minimax optimization of Tuned Mass Dampers under seismic excitation
2011
The present paper concerns the optimal tuning of the free parameters of passive Tuned Mass Damper (TMD) devices, added to benchmark frame structures taken from the literature and subjected to a given deterministic seismic excitation. The tuning procedure is achieved through a numerical optimization approach, namely a Minimax algorithm implemented in a MATLAB environment. Different objective functions have been considered, from both kinematic and energy response indicators of the primary structure. The optimization process is carried-out in time domain, whereby the dynamic response is evaluated numerically by a step-by-step integration based on Newmark’s average acceleration method. In order to assess the efficiency of the proposed methodology and investigate the effectiveness of the so-conceived TMD, several numerical tests on both single- and multi-degree-of-freedom frame structures endowed with a TMD are performed. The salient numerical results are presented in plots and tables. P...
Earthquake Engineering & Structural Dynamics, 2012
It is well established that small tuned mass dampers (TMDs) attached to structures are very effective in reducing excessive harmonic vibrations induced by external loads but are not as interesting within the context of earthquake engineering problems. For this reason, large mass ratio TMDs have been proposed with the objective of adding a significant amount of damping to structures, thus constituting a good means of reducing structural response in these cases. This solution has other important and attractive dynamic features such as robustness to system uncertainties and reduction of the motion of the inertial mass. In this context, this paper aims to describe an alternative methodology to existing procedures used to tune these devices to earthquake loads and to present some additional considerations regarding its performance in controlling seismic vibrations. The main feature of the proposed method consists of establishing a direct proportion between the damping ratios of the structure's first two vibration modes and the adopted mass ratio. By equalizing the damping ratios of the system's main vibration modes, this proposal also facilitates the use of simplified methods, such as modal analysis based on response spectra. To demonstrate the usefulness of this alternative methodology, an application example is presented, which was also used to perform a parametric study involving other tuning methods and to estimate mass ratio values from which there is no significant advantage in increasing the TMD mass.
Shock and Vibration
Passive energy devices are well known due to their performance for vibration control in buildings subjected to dynamic excitations. Tuned mass damper (TMD) is one of the oldest passive devices, and it has been very much used for vibration control in buildings around the world. However, the best parameters in terms of stiffness and damping and the best position of the TMD to be installed in the structure are an area that has been studied in recent years, seeking optimal designs of such device for attenuation of structural dynamic response. Thus, in this work, a new methodology for simultaneous optimization of parameters and positions of multiple tuned mass dampers (MTMDs) in buildings subjected to earthquakes is proposed. It is important to highlight that the proposed optimization methodology considers uncertainties present in the structural parameters, in the dynamic load, and also in the MTMD design with the aim of obtaining a robust design; that is, a MTMD design that is not sensi...
Optimal tuned mass damper for seismic applications and practical design formulas
Engineering Structures, 2008
In seismic retrofit of a long-span truss bridge in Japan, a new retrofit scheme was applied in which the existing bearings of the bridge were replaced by a new floor deck isolation system. The floor decks and isolation system together can be viewed as a giant tuned mass damper (TMD) to reduce the seismic force of the truss. This motivates a study on the optimal design of a TMD for a single-degree-of-freedom structure under seismic loads in this paper. Kanai-Tajimi spectrum is selected to model the earthquake excitation. It is shown that, when ratio of the characteristic ground frequency in the Kanai-Tajimi spectrum to the structural frequency is above three, the ground motion can be assumed to be a white noise to design TMD. For a smaller ground frequency ratio, simple formulas of the optimal TMD parameters are obtained. The dependence of optimal TMD parameters on mass ratio especially for large TMD is highlighted. It is found that the optimal TMD has lower tuning frequency and higher damping ratio as the mass ratio increases. For a large mass ratio, TMD becomes very effective in minimizing the primary structure response and robust against uncertainties in the parameters of the system.
On tuned mass dampers for reducing the seismic response of structures
Earthquake Engineering & Structural Dynamics, 2005
This paper presents an energy-based theoretical model for a two degree-of-freedom mechanical system. After a general formulation in Appendix A, the model is specialized to study tuned mass dampers as a means to substantially increase modal damping in order to induce a consequential decrease of the seismic response of the structures thus provided. Although approximate since it neglects coupling due to damping, it is shown that the model yields a ÿrst-order approximation to the exact frequencies, providing values of optimum damping that closely match exact results proposed by others. In view of this, it is proposed that the model be applied through an iterative numerical procedure that identiÿes the pertinent optimum parameters. It is also shown that for certain particular benchmark cases the model provides closed-form equations for the parameters deÿning the dynamic states related to these special conditions. Despite its approximate nature the model presented in this paper is rational, and due to its explicit consideration of energy balance and overall simplicity, it provides a convenient platform for the study of tuned mass dampers, as well as for other methods of structural passive control. Copyright
Optimum Tuned Mass Dampers under seismic Soil-Structure Interaction
Soil Dynamics and Earthquake Engineering
Tuned Mass Damper (TMD) devices are widely adopted as a valid mechanical solution for the vibration mitigation of structural systems and buildings under dynamic excitation. In the specific challenging context of seismic engineering, TMDs may represent a convenient option for both aseismic structural design and seismic retrofitting. However, the expectable efficiency rate of TMDs in that context is still debated. Besides, potential Soil-Structure Interaction (SSI) effects may become crucial in the mechanical system, and should properly be taken into account for the optimum TMD design, in order to avoid possible de-tuning. This work contributes to this framework, by investigating the effectiveness of an optimum TMD in reducing the linear structural response to strong-motion earthquakes of a given set of Multi-Degree-Of-Freedom (MDOF) low-and high-rise shear-type frame structures, by embedding SSI within the dynamic and TMD optimisation model. The TMD is seismically tuned through a dedicated two-variable optimisation procedure, for each specific case (primary structure, seismic event and soil type), therefore providing the optimum device setting for each given context. Average primary structure response indices are specifically targeted to that purpose, while maximum ones are monitored. A quite considerable range of optimisation cases is considered (eighty instances), to outline rather general considerations and average trends on TMD optimisation and effectiveness within the seismic SSI framework, for both low-and high-rise buildings. Such an investigation shall provide useful guidelines for a comprehensive tuning of TMDs in mechanical systems and specifically in the presence of seismic SSI, to be consulted in view of real-case applications.
Passive Tuned Mass Damper for Seismic Protection
2013
One of the approaches to reduce excessive oscillation on buildings due to dynamic forces is represented by installing a passive mechanical device called tuned mass damper (TMD). This paper presents a study on the effectiveness of TMD in reducing the response of structures that are subjected to seismic excitation. The earthquake accelerograms of El Centro’40 and Kobe’95 are considered, and a two-dimensional linear-elastic model with TMD on the top is used in performing dynamic analysis.
Discussion of system intrinsic parameters of tuned mass dampers used for seismic response reduction
Structural Control and Health Monitoring, 2015
Assimilating the structures incorporating tuned mass dampers to 2-degrees-of-freedom mechanical systems, this paper discusses the salient parameters defining the efficiency of these devices when affixed to structures for the purpose of seismic response reduction. Focusing on parameters that are intrinsic to the mechanical systems and independent of ground motions, numerical and analytical expressions are first obtained for the modal damping of the systems. Subsequently, it is proposed that the highest efficiency in terms of modal damping allocation is achieved at tuning that results in modal damping that is in the same proportion as the participation factors for the modes. Further, some properties of the frequencies, tuning, and participation factors are analytically demonstrated. Finally, limited numerical calculations using a spectrum-compatible accelerogram are offered to support the proposed method for modal damping allocation.