This work presents an analysis of the main procedures developed to calculate fracture toughness under elastoplastic conditions. The main measures of toughness, differences, characteristics, and sources of conservatism are evaluated. Also, the main bibliographies reporting differences in calculation methods to predict failure loads in flawed structures are examined. Lastly, the main assessment procedures of Structural Integrity of structures with flaws (fitness for service, FFS) are also analyzed.Toughness tests are performed varying the constraint conditions near the crack tip (geometry, initial crack size, side grooves). JR curves and fracture load predictions were made according to the principal FFS procedures. Also, experimental tests are performed on centrally cracked plates in order to record the failure loads of the structure, to compare them with the predictions of FFS procedures and to evaluate their conservatism. Other contributions of this work are numerical simulations of toughness tests, developed in order to reproduce the tests and calibrate the simulation parameters of ductile tearing in structures with flaws.