Fatigue strength of repaired welded connections made of very high strength steels

Modern steel manufacturing techniques make it possible to produce steel with the nominal yield strength up to 1300 MPa for structural purposes. However, the application of very high strength steels is still limited in the civil engineering structures due to lack of knowledge about the effects of the manufacturing process and experimental results regarding the structural behaviour of the material. Moreover, in a fatigue loaded very high strength steel structure absolute and relative stress variations will be higher compared to stresses in structures made of lower steel grades. Accordingly, the fatigue issue will be one of the most important design criteria for very high strength steel structures. In this current study, V-shape welded specimens were manufactured from S690 and S890 rolled steels and cast steels with similar yield strengths. Fatigue cracks were created in the weld toe of the specimen under a fluctuated loading and subsequently the fatigue damaged specimens were repaired by the removal of the cracks with subsequent welding. The fatigue strength curves of repaired specimens are compared with the detail categories of EN 1993-1-9 [8] and the fatigue strength curves of the test results in the as-welded condition from literature. The fatigue strength of the fatigue damaged connections was completely recovered by the established repair procedure.