Structural Vibration
The effects of structural vibration on buildings are little understood, often resulting in costly and conservative measures being undertaken in an effort to mitigate potential problems. Bill Jordan & Associates has developed a high level of capability in the evaluation of the vibration vulnerability and behaviour of a large range of building and structure types which are subject to vibrations from blasting, construction works and earthquakes. Projects start with the simple evaluation of likely vulnerability by consideration of the structural form and materials. Detailed monitoring of the structure using sensitive equipment, and the subsequent analysis of the recorded behaviour using specialised software, yields further information, sufficient to satisfy any requirement.
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A wide range of structures has been evaluated for vulnerability to ground vibration from mining and construction works. Evaluations can range from simple assessments involving building form, materials and generalised vibration parameters to detailed monitoring over many years with input into blast design.
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Sensitive accelerometers can be attached to buildings without causing damage to sensitive heritage fabric. The principal location is usually on corners to evaluate building swaying, or racking, which can do most damage. Up to 12 such accelerometers with two recorders are available for deployments which can be for the duration of a blast or for extended periods when wind effects can be determined. |
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Special software has been developed in ‘Matlab’ to analyse both the ground waves and the building vibrations. In many cases the various waveforms can be correlated to millisecond accuracy using GPS receivers.
Shown are spectrograms from a building recorded with an accelerometer and one of the ground wave recorded by a geophone in a corresponding direction.
The acceleration, velocity and displacement waveforms are also shown for the same recordings. The time scales correspond.