Abstract: The functional relation between the reliability and the service time of a structural member or a danger position on structure is established. The safe-life design, the damage tolerant design and the crack detection capability of nondestructive testing methods are considered. On the basis of the functional relation, a new model for reliability assessment of structures is presented. Thus the service life and the overhaul periods with high reliability of a structure are determined by the model,

Key words: reliability assessment, safe-life design, damage tolerant design, probability of crack detection