Figure 21: Strain Gauges Mounted On Flanges; Figure 22: Axial Strain Measurement/Bending Moment About Yy Axis - Geokon 4100 Series Instruction Manual

18 | GAUGE LOCATION | GEOKON

FIGURE 21: Strain Gauges Mounted on Flanges

For reasons of economy, if it is decided that only two strain gauges per cross-
section are to be used, then the configuration shown in the figure below may be
used. This configuration will give the axial strains and the bending moment
around the minor YY axis only.

FIGURE 22: Axial Strain Measurement/Bending Moment About YY Axis

This configuration allows for easy protection of the instruments and their cables.
If desired a hole may be drilled in the web so that the cable from one gauge may
be passed through to the other side, allowing both cables to be protected by a
single conduit.
Another possible two-gauge configuration is shown in Figure 23.
This configuration allows the calculation of the axial strains and the bending
moment around the major XX axis. A disadvantage lies in that the exposed
position of the gauges on the outside of the flanges requires a greater degree of
protection. Also, local bending at one gauge may not be felt by the other gauge.
A real world example of this was seen when welding on the exposed flange of a
soldier pile close to one gauge produced large strain changes which were not
felt by the other gauge on the back side of the pile.
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