IDEERS Research@Bristol - Forced Vibration Tests on a Reservoir Tower

To find out how a tower in water vibrates. When the tower vibrates, it moves around in the water setting up pressure waves in the reservoir. The water pressures, in turn, exert a force back on the tower. Engineers need to know how this happens, so that they can calculate the forces on an intake tower when it vibrates during an earthquake. Then they can design a tower that is strong enough to resist earthquakes.

This pressure transducer was designed to measure air pressures, so the back of it and its cable were not watertight. To use it in water, the cable connection was housed in a specially made watertight aluminium cylinder, and the cable was threaded through plastic tubing.

Forced Vibration Tests

Intake Tower at Wimbleball Lake, Somerset
(Where is it?)
(Click to see inside view of tower)

Special test machines called "Rotating Eccentric Mass Exciters" were used to vibrate the Wimbleball intake tower. (Why?) Three of them were lowered into the 50 metre high, reinforced concrete tower (Show Me), and bolted down on different floor levels (Show Me).

The tower is connected to the top of the buttress dam by a bridge. When the tower vibrated, it caused the bridge and dam to vibrate too. The vibrations of all these structures were measured using accelerometers. The movement of the tower also set up small vibrations in the reservoir water, which caused the water pressures to fluctuate.

The changing water pressure on the face of the tower was measured with an electronic instrument called a pressure transducer. (Show Me) The pressure transducer and cable were lowered down from the top of the bridge (Show Me) and guided down the face of the tower using a specially made weighted wheel. (Show Me)

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Reservoir Towers
Forced Vibration Tests

from Bristol University