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Non-Asphaltic Fatigue Damage
A damage function similar to the one used for fatigue damage of asphaltic materials may be used for generic non-asphaltic bound materials. It is based on the maximum tensile strain at the bottom of the layer. The fatigue damage is calculated using the following equation and the time hardening procedure:
where MN is the number of load repetitions in millions,
ε is the horizontal tensile strain at the bottom of the layer in the longitudinal direction,
εref is the reference strain,
E is the modulus of the material (adjusted for climate and damage),
Eref is the reference modulus, and
A, a, b and g are constants.
The modulus of the layer is reduced by multiplying the intact modulus by (1 - w), where w is the fatigue damage. To avoid unreasonably low stiffness, the damage w must be no more than wmax which is set to 0.9 by default:
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