Recently the technological evolution in structural steels, particularly in the area of offshore and marine applications, seems to point to a trend towards an increasing use of high strength weldable steels. Accordingly, the need to develop specific knowledge about the fatigue behaviour of high grade steel welded joints is becoming a more crucial issue. In parallel with these developments a consistent improvement, both in the mechanical properties of consumables and in welding technologies, has been achieved in order to guarantee high-quality/high-strength steel welded joints for lightweight structures.
In this context was born the FATHOMS project aimed at an improvement in knowledge on the fatigue behaviour of welded joints in high strength steels (specified minimum yield strength ? 420 MPa), contributing to improve design criteria for welded structures and components for offshore applications, in terms of reductions both in weight and cost. The final goal of the proposed project is to produce and collect valuable information to extend the applicability of design standards to the use of high strength steels in welded structures.
In particular in order to achieve the above mentioned goal the work will be mainly focused on the evaluation of:

• the eventual conservativeness of both the selected design S-N curves and the fatigue damage tolerances recommended in the Standards when high steel grades are used;
  
• the influence of loading conditions similar to those encountered in service (e.g. high R or ?mean values and selected load spectra), together with various external environments (such as cathodic protection in sea water), in conjunction with the use of new welding technologies and post-weld treatments.
  

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