Examples of Semi-Active Structures

Damping Fr., Effective Damper Mass.

Control Mechanism

Building

0.53 Hz, 18.2t

Tuned Liquid Dampers (720)

TYG Building, Atsugi (159m)

330t

Active Tuned Mass Dampers (3)

Shinjuku Park Tower, Tokyo (227m)

0.185Hz, 340t

Active Tuned Mass Dampers (2)

Yokohama Landmark Tower (296m)

0.33 – 0.62Hz, 270t

Passive Tuned Pendulum

Rokko Island P&G, Kobe (117m)

0.1, 0.5Hz, 220t

Passive Tuned Pendulum

Sydney Tower (305m)

0.14 Hz, 2 x 300t, 4% damping ratio

Two Passive Tuned Dampers

John Hancock Bldg, Boston (244m).

Passive Tuned Mass Damper

CN Tower, Toronto (533m).

Engineering Structures, Vol. 17, No. 9, Nov. 1995.

Passive Control: Base Isolation

Base isolation is a mature technology, commonly used in bridges. Pictured left is a base isolator in use on a building at the Kajima Research Facility. Pictured on the right are base isolators used in a viaduct in Nagoya. These structures rely on (passive) base isolation to control the structure in the event of ground motion (Picture credits Steven Williams).

Multistep Pendulum Dampers

The Yokohama Landmark Tower, one of the tallest buildings in Japan relies on multistep pendulum dampers (2) to damp dominant vibration mode of 0.185 Hz. Pictured on the right is a model of the pendulum (Picture credits Steven Williams).

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Examples: Active Mass Damper in the Kyobashi Seiwa Building

An Active Mass Damper consists of a mass whose motion (displacement, velocity, acceleration) is controlled, in this case, by a turn-screw actuator. Eigenvalue analysis of the structure shows that the dominant vibration mode is in transverse direction with a period of 1.13 s. and second eigenvalue in the torsional direction with a period of 0.97s. The two-mass active mass damper damps these two modes (Picture courtesy BolognaFiere).

Passive / Semi-Active Fluid Dampers

Pictured left is a passive fluid damper with bottom casing containing the bearings and oil used to absorb seismic energy. Pictured right is a semiactive damper with variable orifice damping (Picture credits Steven Williams).

The Future: Fine-Grained Active Control.

A new class of active dampers based on Magnetorheological Fluids (fluids capable of changing their viscosity characteristics in milliseconds, when exposed to magnetic fields, courtesy Lord Corp.), coupled with considerable advances in sensing and networking technology, present immense potential for fine-grained real-time control for robust structures. These control mechanisms render structures resilient to explosions and failures due to anomalous conditions such as high-temperature, in addition to traditional hazards such as high winds and earthquakes.

Active Control: Emerging Frontiers

The Dongting Lake Bridge is being retrofitted with MR dampers to control wind-induced vibration (picture source: Prof. Y. L. Xu, Hong Kong Poly.)

Examples of Active Structures

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2004-02-09T11:31:20

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