Optimal design of a damped dynamic vibration absorber for vibration control of structure excited by ground motion

BY- SHRIKANT DHOLE

GUIDED BY- M C RAY AND K RAY

INTRODUCTION

1 •What are dynamic vibration absorbers?

2 •Undamped dynamic vibration absorber

3 •Traditional damped dynamic vibration absorber

4 •A variant form of the damped dynamic vibration absorber

5 •Comparison

6 •Conclusion

What are dynamic vibration absorbers?

A machine or a system may experience

excessive vibration if it undergoes resonance. In

such cases the vibration of machine or system

can be reduced by using

a vibration absorber.

Dynamic Vibration Absorbers (DVA) are

based on the concept of attaching a secondary

mass to a primary vibrating system such that the

secondary mass dissipates the energy and thus

reduce the amplitude of vibration of the primary

system.

Undamped dynamic vibration absorber

Traditional damped dynamic vibration absorber

• Undamped vibration absorber introduces two new peaks thus the machine experiences large amplitudes as it passes through the first peak during the start up and stopping.

• Undamped absorber has poor bandwidth.• Small damping extends bandwidth.• But, ruins complete absorption of motion.• Becomes a design problem to pick the most favorable ℓ, ζ, ξ.

(optimum ratio of natural frequency (ζ) and optimum damping (ξ) )

Why damping in the absorber ?

Traditional damped dynamic vibration absorber

Traditional damped dynamic vibration absorber

Traditional damped dynamic vibration absorber

A variant form of the damped dynamic vibrationabsorber

A variant form of the damped dynamic vibrationabsorber

A variant form of the damped dynamic vibrationabsorber

A variant form of the damped dynamic vibrationabsorber

A variant form of the damped dynamic vibrationabsorber

Comparison

Comparison

Comparison

CONCLUSION

▪ Under the optimum tuning condition of the absorbers, it is proved analytically that the proposed absorber provide a larger suppression of resonant vibration amplitude of the primary system excited by ground motion than the traditional absorber.

▪ The comparison revealed that though model B requires a larger amount of damping than model A, the resonant vibration amplitude under the optimized condition of model B is always less than that of model A. It provides an alternative design for the traditional damped dynamic vibration absorber.

References

•W.O. Wong, Y.L. Cheung / Engineering Structures 30 (2008) 282–2861•Theory of vibration by Thomson2•Mechanical vibration by SS Rao3