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Suspension bridge in Cornwall

The suspension bridge spans 47m over a road in Cornwall, England. It has a 3.5m wide deck made of FRP composites, and it is suspended by steel cables and hangers. Noise/vibration from the busy road and wind were natural excitation for the bridge that was utilised to perform ambient-based modal testing. Photos of the bridge are shown in Figure 1.

Ambient testing

The acceleration responses to ambient excitation were measured at various points on the deck as well as on the main suspension cables to determine natural frequencies and damping ratios of the structure. Six vibration modes of the deck were identified in the frequency range up to 4Hz. The fundamental vertical mode has natural frequency of 1.91Hz and damping ratio of 2.3%.

Response measurements

The response of the structure to walking and jumping excitation was measured. In addition, tests were performed to investigate if the humans interact with vibrations of this bridge. Figure 2 shows a test with walking and jogging excitation, as well as a (waterproof) data acquisition station. Data analysis is currently being performed and it will be reported in a journal paper in near future.

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Photo Gallery
Accelerometers on deck
Deck accelerometers
Cable accelerometer
Power generator
Interaction test
Bridge underside
Protection from rain