Structures vibration have different origins
- wind and vortex
- earthquake
- walking of pedestrians on a bridge or footbridge
- machine excitation..
Wind exited structure
At a given wind speed vortex are generating around the structure. When the critical wind speed is obtained the structure is a subject to resonance phenomenon. The intensity of the phenomenon is bigger when the structures damping is small.
Case of circular section
Vortex downstream of cylinder leads to high vibration when the frequency of the vortex is near one of the frequency modes of the cylinder.
There is a generation of alternative area in pressure or under pressure.. in the crosswind direction. As a result the cylinder starts vibrating in the crosswind direction.
Example of a vortex downstream of a cylinder.
Case of a bdridge beam
Vortex downstream of a bridge
