Experimental Study on the Effects of Tuned Mass Damper

Experimental Study On The Effects OF TMD 
On Structure Vibration Reduction 
 5. Getting Data [26]
M H Pashaei(1), H Sheydaie (2) I  Khatami (3)  MUsing experiment equipment we come to a
jazayeri (4)time-displacement graph which is being showed in Fig
 11 , 12 .the first graph shows the displacement of
            School of Engineering, Universitystructure under the  free vibration using TMD and the
of Mazandaran, P O Box: 484, Babol, Iransecond one not using TMD.
Email: (1)  , (2)(3) 
  , < >(4) 
  
___Abstract                              
Damping is a phenomenon which exists in everyFig 11.Time –Displacement Graph for system without
system. Some systems have little and some haveTMD
more. it is related to what elements and how they are 
assembled with each other in system .such 
phenomena dissipate energy and reduce the vibrating 
caused by external applied forces to system like earth Â Â Â Â Â  Fig 12. Time _Displacement Graph for
quick, wind ,sea wave and thunder .Different types ofsystem with TMD
dampers have been known regarding to their function: 
passive, active and semi-active. In the field of passive 
dampers we have many types: tuned mass damperIt is clear if we confess on both graphs it shows the
TMD, tuned liquid damper TLD, friction dampers FDMaximum Displacement reduce from 1.3 mm to 1.1 mm.
and viscose dampers VD.For all the graph we use the   ‘logarithmic
The present research experimentally studies dampingdecrement’ method to calculate damping ratio  .
ratio of a three-storey building using TMD and withoutFig 13 shows a graphical representation of a damped
TMD damper to see how damper increase thefree vibration. The motion shown in Fig 13 may be
damping ratio . To carry out this study A  structurerepresented by the equation:
and the necessary equipment including a loading 
system and a data acquisition system are used..                     
Structure examined under the free vibration in this Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  (3)
way: A small displacement implemented to the                       
structure as a free vibrations. And by carrying outWhere
more than 150 tests, the damping ratios of the 
structure using TMD and without TMD in different 
loading conditions are obtained. The results show that 
the Tuned mass damper has a major effect on theIs the natural frequency, is the damping ratio of the
damping characteristics of the structure The resultssystem and X and are arbitrary constants determined
also show that the increasing the loading applied tofrom initial conditions.
structure doesn’t change the damping ratio which isThe natural logarithm of the ratio of any two
analyses an Ansys software .successive amplitudes, for example  and  in Fig 1,
Key Word: damping ,tuned mass damper ,dampingcan be written as:
ratio           
___ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  (4)
1 IntroductionWhere  and can be obtained from Eqn 3 at t=t1 and
 t=t2=t1+τ, respectively. Inserting these values of  and
1.1 Damping concept in Eqn 4 will result in the following equation:
Damping is a phenomenon where the amplitude of           
vibration in a mechanical system steadily diminishes. Â Â Â Â Â Â Â 
The effect of damping is to remove energy from the Â Â Â Â  (5)
system. Energy in a vibrating system can beFor every step of loading we get the result showed in
dissipated, being converted into heat [1,2,3]. Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 
  
  Â Â  Table 1
Damping is present in all vibrating systems. Every 
system which possesses mass and elasticity is6. Results
capable of vibration. Dampers are kind of device in- Damping ratios change with applying different loads
order to dissipate vibration forces... Different types offor the system not using TMD instead it will not change
dampers have been known .in general they are dividedfor system using TMD .thus it can be show that using
in three categories: passive, active andTmd increase the damping ratio but if the amplitude of
semi-active.[4,5,6,7].Tuned liquid dampers[8] and Tunedsystem increase cause by Appling more forces, it will
mass dampers[9] are  very usual one which are usingnot change.  . A Tuned Mass Damper has constant
nowadays in many structural system and the secondbehavior.
one is our research topic.- For optimize performance of TMD it is better to
 design optimum range of 0 to 2% of mass and
2 Examined modelstiffness of real structure 
 . If we suppose the structure like a cantilever beam,
In present research A  structure is being designedthe edge of the beam has more displacement during
and built as a model of a real structure in Fig.1vibration, so it is rational to locate damper where there
 is more displacement.
                        
 Â Â Â Â Â Â Â Â Â Â Â  Fig 1: drawing and picture of 
model 
 the weight of the structure is 200 kg  and the 
stiffness of that is k=6.666 N/mm and  the natural 
frequency is w=0.056 Hz which  was analyses in a 
finite element software Ansys 
 Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Fig 2: analysed model 
in software 
  
3 TMD design [11~25] 
 in order to design the TMD with study of many 
books and article and the real TMD used in some real 
structures in the world like Citicope tower in New York 
[10]  we came to this  result :  the mass of TMD 
can consider 2 percent of structure’s mass or less, 
but it should be design in a optimum way . NaturalReference
frequency of TMD Should be as the natural frequency 
of real structure. When the real structure approach to 
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 Â Â Â  Fig 1023- 11th International Conference on Structural
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