The present work pertains to the numerical prediction of the current residual strength of large metallic engineering structures when submitted to accidental overloads. In this context, is developed a unified 3D numerical methodology reproducing the successive stages of the progressive failure of structures made of ductile metals, viz. (i) more or less diffuse micro-voiding induced damage, (ii) strain/damage localization in a narrow band, and (iii) macro-crack formation and propagation. This is notably realized via a combination of the GTN model and an XFEM/CZM coupling. Localization is addressed here as a phenomenon driven either by plastic instability or void coalescence. In the latter case an original transition criterion is proposed, accounting for the competition between Mode I/II type localization, utilizing the local triaxiality as a mode indicator. The methodology is implemented as a user element subroutine (UEL) within the commercial finite element computation code ABAQUS and its performance is assessed considering 3D numerical simulations of various loading cases. The proposed methodology is shown to be mesh objective and able to fairly reproduce ductile crack patterns, while it gives promising results regarding global specimen responses.