4 - Viscous fluid dampers

Viscous fluid dampers are similar to shock absorbers in a car. They consist of a closed cylinder containing a viscous fluid like oil. A piston rod is connected to a piston head with small holes in it. The piston can move in and out of the cylinder. As it does this, the oil is forced to flow through holes in the piston head causing friction.

When the damper is installed in a building, the friction converts some of the earthquake energy going into the moving building into heat energy.

The damper is usually installed as part of a building's bracing system using single diagonals. As the building sways to and fro, the piston is forced in and out of the cylinder.

Viscous fluid damper installed in building


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from Bristol University