Interpreting Strain Measurements from Load Tests in Bored Piles

In static load tests vibrating wire strain gages are generally used. The advantage of vibrating wire sensors over more conventional electrical resistance or semi-conductor types lies mainly in the sensor output, which is a frequency rather than a voltage or resistance. The frequency output is easier to transmit over long cables and is unaffected by voltage drops such as those which can be brought about by corrosion of terminal contacts, moisture penetration into either the sensor or the signal cable, or temperature effects on the cable, all of which would radically affect the output of electrical resistance types. Also, shortening or lengthening of the sensor cables does not affect the frequency signal.