Bridge Vibrations

To study the resonant modes of a tied arch bridge, the bridge is first hit with a hammer or your hand. An FFT of the resulting vibrations are examined to find resonant modes. Then the bridge is driven with a sinusoidal force having each of the resonant frequencies.

The vibrations are detected using five load cells which act as accelerometers, placed at even spacing along the span of the bridge. For any particular resonant mode, a single load cell may be accelerating a lot or it may be stationary, depending on where the nodes of the oscillation are.

The driving force is provided by a speaker powered by a signal generator and attached to the bridge using a rubber band so the speaker both pulls and pushes the bridge in a sinusoidal motion. The driving force is measured by a load cell attached between the bridge and the rubber band.

You can introduce a flaw in the bridge by removing one or more of the I-beams and then repeat the experiment to see how the vibrations change.

Grade Level: College

Subject: Engineering

Student Files

	Building Tied Arch Bridge Part 1	3.85 MB
	Building Tied Arch Bridge Part 2	4.23 MB
	Bridge Vibrations	2.59 MB
	Bridge Vibrations	6.18 MB
	Bridge Vibrations	1.78 MB

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