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APPENDIX H - TWO STRAIN GAGES MOUNTED ONE ABOVE THE OTHER
Where only one surface of the straining member is accessible then two strain gages can
be used one mounted above the other, to separate axial strains from strains due to
bending.
E
1
and
E
2
are two measured strains at distances
d
1
and
d
2
from the neutral axis of a
steel member (e.g. a sheet pile)
If R = d
2
/d
1
The Axial Strain
along the neutral axis
=
(RE
1
- E
2
)/ (R-1)
The Bending Strain at a distance d
1
from the neutral axis
= (E
2
– E
1
)/(R-1)
Neutral Axis
Ε
2
Ε
1
d
1
d
2