Strain gauges are attached directly to the surface of the structure or are embedded within the structure to sense the extension and compression in the structure itself. Each strain gauge consists of two end blocks with a tensioned steel wire between them. As the strain gauges undergo strain, the end blocks will move relative to each other. The tension in the wire between the blocks will change accordingly, thus altering the resonant frequency of the wire. Vibrating wire readout is utilized to generate voltage pulses in the magnet / coil assembly located at the center of the strain gauge. The magnet / coil assembly plucks the wire and measures the resulting resonant frequency of vibration.
The uses of strain gauges are continuous as they are robust and can be deployed / used in any environment and circumstance. Generally, strain gauges are used in pile instrumentation and strut monitoring, however they may also be used to measure stresses in raft foundation and columns.
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