This paper relates to pre-stressed cracked beams, subjected to static long-term service loads. This study is based on the nonlinear differential equations of the concrete matrix creep theory which reflects the correlation between the matrix stress and strain by its modulus of elasticity. For crack predictions, virtual work principles are used to estimate (a) transient strains due to the matrix creep and shrinkage, (b) the resulting stress redistribution, as well as (c) the displacement variations in the beams and (d) the pre-stressing losses in the high yield tendons. A series of laboratory experiments are used to support the numerical evaluations said at points (a) - (d) in addition to (e) calibrating the pre-stressing losses, (f) predicting the beams' stiffness and strength by determining their flexural and nonlinear creep capacity and hence, (g) devising a definition for structural durability and reliability, with regards to the concrete stress-strain relationship under service loads.
