05st08f vibration control of structures

8/10/2019 05ST08F Vibration Control of Structures

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Active Control System (AMD) contdBecause a desirable property is to make it easy to implement,the active damping device is based on an inertial actuator acollocated vibration sensor (for robustness) and a simplecontroller implementing a direct velocity feedback (DVF)

Fig 1


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Active Control System (AMD) contd

Actuator under the Rooftop Heliport in theApplause Tower, Osaka, Japan

Fig 2 Fig3

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Passive Control SystemA passive control system does not require an external powersource.

Passive control devices develop mechanical forces within themselves in response to the motion of the structure.

Passive control depends also on the initial design of thestructure.

A passive control system is is relatively inexpensive, itconsumes no external energy, it is inherently stable and itworks even during a major earthquake.


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Passive Control System contd

Tuned Mass Damping (TMD):The properties of this device are tuned to the naturalfrequency of the building to reduce resonant vibrations onthe structureA proof mass (roughly 1 to 2% of the building mass) placedwithin the upper portion of a structureSprings and dampers connect mass so that the damping ofthe structure is increase at 1st mode as shown in fig


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Fig4. Tuned Mass Damper in Structure Fig 5.Tuned Mass Damper


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Metallic Yield Dampers:Layers of mild steel intentionally intended to deform andwarp under earthquake loadings thereby reducing energyimparted to a structural system.Metallic yield dampers rely on the inelastic deformation ofmetals to dissipate energy.

Fig 6. X-PlateMetallic Damper


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Viscoelastic Dampers:Contains a viscoelastic polymer sandwiched between twometal plates.

Viscoelastic polymer deforms through shear action removingenergy from the system.


Fig 7


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Friction Dampers:The systems, carefully controlled by a sliding surface,feature a very large initial stiffness and the possibility ofnearly perfect rectangular angular hysteretic behavior .Uses the friction between steel plates sliding over eachother to dissipate seismic energy.There are two types of Friction Dampers,

Rigid frame Friction Dampers

Braced frame Friction Dampers



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Fig 8Back to Types


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Hybrid Control SystemThese control techniques involves combination of both activeand passive control systems.

Hybrid Mass Dampers (HMD)It is a combination of Tuned Mass Dampers (TMD) withactive Actuators.It relies more on the natural motion of the Tuned MassDampers, whereas actuators are used to increase efficiency and robustness.Also in this category is the Active Passive Tuned MassDampers as shown in the Fig 9


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Hybrid Control System contd

Fig 9 Active-passive tuned mass damper (APTMD)


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Semi-Active Control SystemSemi-active control devices cannot inject energy into thecontrolled system, but have mechanical properties that canbe adjusted to improve their performance.

Variables-orifice dampersVariable-orifice dampers consist of conventional hydraulicfluid dampers adapted with controllable, electromechanical,variable-orifice valves that change the flow resistance andtherefore alter the amount of damping provided to thestructure.


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Variable-stiffness control devicesThese systems have the ability to modify the structures stiffness and therefore its natural frequency, to avoid resonant conditions.

Adjustable tuned liquid column dampersThese devices, as passive TLDs, use the sloshing of a liquid, causedby the motion of the structure , to reduce structural vibrations.

Controllable fluid dampers1. Electro-Rheological (ER) Dampers2. Magneto-Rheological (MR) Dampers

Semi-Active Control System contd


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Magneto-Rheological (MR) Dampers An MR damper resembles an ordinary linear viscous damper;however, the cylinder of the MR damper is filled with aspecial fluid that contains very small polarizable particles .When no current is supplied to the coil, which is wrappedaround the piston of the damper, an MR damper behavessimilar to an ordinary viscous damper.Since the control force is not applied directly they are morestable.

Semi-Active Control System contd


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ConclusionsA discussion of the various techniques used to mitigatebuilding motion was presented.

This presentation addressed a number of passive and activepresentation loads for human comfort considerations , as wellas several seismic applications.

While the incorporation of such technologies permit todaysstructures to reach even greater heights , and to resist theseismic effects.

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ReferencesRWDI, Consulting Engineers and Scientists Spencer, B.F. Jr., and M.K. Sain (1997), ControllingBuildings: A New Frontier in Feedback, IEEE ControlSystems, 17(6): 19-35. Takenaka Corp , AMD System in Herbis Osaka, Companybrochure

Yukio Tamura, (1996) Mitigation of Motions of TallBuildings with Specific Examples of Recent Applications

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05st08f vibration control of structures

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