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This paper presents the derivation and experimental verification of analytical expressions for assessment of fatigue crack closure. The expressions are obtained based on the modification of the Rigid-Insert Crack Closure (RICC) model for the load-line of the C(T) sepcimen. The formulation of the model results in a set of equations which can predict the closure load as well as the Load-COD characteristics using the residual COD at zero load as a unique experimental input. The final form of the derived equations are rather complex and require a numerical solution. The equations are verified, both qualitatively and quantitatively, using different specimen sizes and 7075 aluminum alloy and specially designed experimental techniques