A new technique using prestressed carbon fiber laminates (CFRP – Carbon Fiber Reinforced Polymers) is being developed to repair fatigue cracks or prevent fatigue cracking on riveted bridge members. High fatigue resistance and high tensile strength of carbon fibres allows the use of bonded CFRP-plates for crack patching. Prestressed CFRP-plates bonded on cracked steel sections slow down or stop completely crack propagation by acting in three different ways: (1) by increasing the stiffness of the cracked steel sections, (2) by reducing crack opening displacements at and behind the crack front and (3) by applying compressive stresses and producing a crack closure effect. The effectiveness of this technique is verified by a parametric study using small and full scale fatigue tests and numerical models.