Study of wind-induced vibrations in tall buildings with tuned mass dampers taking into account vortices effects
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Abstract:
In recent years, construction of tall buildings has been of great interest. Use of lightweight materials in such structures reduces stiffness and damping, making the building more influenced by wind loads. Moreover, tall buildings of more than 30 to 40 stories, depending on the geographical location, the wind effects are more influential than earthquakes. In addition, the complexity of the effects of wind flow on the structure due to the interaction of the fluid flow and solid body results in serious damages to the structure by eliminating them. Considering the importance of the issue, the present study investigates the phenomenon of wind-induced vibration on high-rise buildings, taking into account the effects of vortices created by the fluid flow and the control of this phenomenon. To this end, the governing equations of the structure, the fluid flow and the tuned mass damper (TMD) are first introduced, and their coefficient values are extracted according to the characteristics of ACT skyscraper in Japan. Then, these three coupled equations are solved using a program coded in MATLAB. After validation of the results, the effects of wind loads are analyzed and considered with regard to the effects of vortices and the use of TMD, and are compared with the results of the state where no vortices are considered. Generally, the results of this study point out the significance of vibrations caused by vortices in construction of engineering structures as well as the appropriate performance of a TMD in reducing oscillations in tall buildings.Keywords:
Vortex-induced vibration
Wind engineering
Tuned mass damper
This paper investigates the influence of the story stiffness of reinforced concrete (R/C) frame on the seismic response of R/C buildings with proportional hysteretic dampers. For this purpose, non-linear time-history analyses were conducted on a series of multi-degree-of-freedom system models that include a wide range of structural parameters and vertical distributions of story stiffnesses and strengths of R/C main frame and dampers. Although the basic purpose of damper installation is to reduce deformation demands, the results of analyses indicate that the story-drift demand on an entire system could be larger than that of the structure without dampers, depending highly on the stiffness and response period of R/C main frame. Moreover, dampers are shown to be more efficient in reducing the story-drift demand when installed into a flexible R/C main frame.
Structural system
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Researches distributed vibration damper. Based on the theoretical analysis, the theoretical calculation and polyplan experiments are carried on wide band damping augmentation of the distributed vibration damper. Then, the results of the theoretical calculation and model experiments show the distributed vibration damper can greatly increase dissipation of vibration energy and can further reduce vibration amplitudes compared to traditional lumped damper.
Tuned mass damper
Damping torque
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It is well-known that, Tuned Mass Dampers (TMD) are installed to regulate the dynamic vibrations. In this study optimum parameters one of thepast classic study is used. Tuned Mass Damper (TMD) is a passive control device which absorbs energy & reduces response of vibration. It is attached to vibratory system.The criteria used to obtained the optimum parameter is to choose for a given mass ratio, the frequency ratio and damping ratios that put result in equal and large model damping in the first two prominent modes of vibrations. The parameters are used to compute, the responses of several single and multi-degree of freedom with TMDs to different earthquake excitations.In the present study, performance of Three TMDs are compared. The mass ratio for those TMDs are taken as 30%, 40% and 50%. It is shown that large mass of TMD is more robust and effective in reducing the response under earthquake.
Tuned mass damper
Mass ratio
Damping ratio
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A new damper system called Lever Mass Damper(LMD)for vibration control of inclined cables on cable-stayed bridges is developed,and the structure,damping principle of LMD for vibration suppression are discussed as well.The damping performance of an LMD attached to a stay cable is investigated by solving complex eigenvalue problem with Nonlinear FEM.Compared with an oil damper for cable vibration control,except the 1st mode,LMD can provide higher modal damping ratios and has better performance for mitigation of cable vibration.
Tuned mass damper
Lever
Damping torque
Damping ratio
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In order to mitigate the seismic response of a cable-stayed bridge, a new type damping device named asymmetric pounding tuned mass damper (APTMD) is developed in this paper on the basis of the traditional symmetric pounding tuned mass damper. The novel APTMD has three parameters to be determined: the left-side gap, the right-side gap, and the frequency ratio. A numerical model of the APTMD damping system is established with consideration of both the computational efficiency and accuracy to enable the parametric optimization of the damper. The numerical model is based on a simplified model of the cable-stayed bridge and a nonlinear pounding force model. The genetic algorithm is utilized for the optimization of the damper. Afterwards, the cable-stayed bridge is subjected to 20 recorded ground motions to evaluate the vibration control effectiveness of the APTMD. Four systems are considered: (1) without dampers; (2) with a TMD; (3) with a PTMD; and (4) with an APTMD. Time history analysis reveals the following: (1) those dampers can all effectively suppress the vibration of the bridge and (2) the vibration control effectiveness of the APTMD is slightly better than the TMD and the PTMD.
Tuned mass damper
Bridge (graph theory)
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According to simulation analysis on hysteretic behavior and vibration suppression of the mild steel damper with the diamond-shaped opening and added damping and stiffness,the cyclic loading tests of the dampers and the shaking table test of a fame structure with installed the dampers are computed by the simnlation method.The practicability and accuracy of the simulation methods are proved well by using ANSYS program,and the superiorities of the hysteretic behavior and the vibration suppression of the damper in the overall structures are presented at the same time.
Earthquake shaking table
Tuned mass damper
Hysteresis
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Mechanical vibration dampers (MVD) can be used for reduction of vibrations of tower type structures. A method of determination of optimum parameters of MVD mating with this type of structures is briefly described in the paper. The elaborated computational method became the basis for design solutions. During the last years in Poland, MVD have been applied to reduce vibrations of transmitting antennas installed on the tops of several guyed masts and steel towers. Observations by users of the objects, on which the first group of mechanical vibration dampers had been installed, was presented and analyzed in [1]. Remarks and conclusions placed in the questionnaires of the users of the objects fully confirmed efficiency of these dampers at a considerable range of building's vibration reduction. Since the publication [1] a number of new dampers cooperating with tower structures (masts, steel chimneys) were designed and constructed. New observation results of behavior of the structures with dampers during exploitation have also been collected. All this has been used in this paper for presentation of generalizing conclusions useful mainly for designers of tower type - structures that must be protected against vibrations.
Tower crane
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Tuned mass damper
Natural frequency
Mode (computer interface)
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Many vibration control systems, which are divided into a mass damper system and a storey-installation damper system, for habitability or seismic-safety improvement in high-rise buildings have been developing in recent years. However, a passive energy absorbing system will be the most ideal devices if we consider to reduce the structural responses against the various levels of inputs such from traffic induced vibration to destructive vibration. This study has been developed the vibration control system of an energy absorbing type used the high-damping rubber as a vibration control material. We had already cleared experimentally and analytically that the high-damping rubber damper has stable damping performances in wide vibration area through the various loading tests and the shaking table tests. In this paper, the fundamental performances and the vibration control effects of the full size high-damping rubber damper which was made from the results up to this time is described.
Tuned mass damper
Earthquake shaking table
Damping torque
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The TMD has controlled the vortex-induced vibration of the suspenders of Jiujiang Changjiang-bridge effectively.But after about 20 years,the fatigue failure has emerged on individual dampers because of the frequent large amplitude vibration.Relying on the RD project of TLMD for suspenders of this bridge,the relationship was researched between the mass ratio of TLMD that have been installed and the dynamic magnification factor of main vibration system and the dampers,and the damper amplitude was analyzed in theory in order to prevent the weakening of vibration absorption effect of damper because of fatigue.The study found that: the damper dynamic magnification factor must be no more than 30 through reasonable choice of mass ratio in order to guarantee the safety and reliability of the damper.The project design of the added damper for the the suspenders of Jiujiang Changjiang-bridge was based on this research result.The test result showed that the vibration absorption effect was good and the fatigue failure was not be found.
Bridge (graph theory)
Tuned mass damper
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