UFC 3-220-01N
15 AUGUST 2005
within the range of strain amplitude specified. This assumption is usually made in most
soil dynamics analyses because of the low-vibration amplitudes involved. If the cyclic
hysteresis loops are obtained from triaxial test specimens, the resulting modulus will be
the stress-strain modulus, E. If the tests involve simple shear or torsion shear such that
modulus will be the shear modulus, G. In either case, the same equations apply.
The shear modulus, G, can be computed from the stress strain modulus
and Poisson's ratio as follows:
(12-21)
E
G=
2(1 + )
The shear strain amplitude, Ae, may be computed from the axial strain amplitude, e, and
Poisson's ratio as follows:
(12-22)
Ae = ε(1 + )
For the special case of saturated soils, Poisson's ratio is
0.5, which leads to the following:
G = E/3
Ae = 1.5ε
12-18
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