In this thesis, a new traction stress based method for characterizing shear strength is investigated by carrying out a series of shear strength tests. The AWS method for the calculation of shear strength shows significant discrepancies between longitudinal and transverse specimens. The main purpose of this new traction based definition for shear strength is to demonstrate that there exists a single shear strength value regardless of specimen geometry and loading conditions. With this new approach a better correlation between shear strength values for transverse and longitudinal specimens is achieved. Special issues occur with the multi-pass welds in regards to the failure angle. The AWS equation does not account to different failure angles of the specimens, it only assumes 45o failure angle in all the cases, but the new approach takes into account the different failure angles. Finally with this method a quantitative weld sizing can be achieved for fillet welds.

In this study, ABS Publication 115, “Guidance on Fatigue Assessment of Offshore Structures” is briefly reviewed. Emphasis is on the S-N curves based fatigue assessment approach of non-tubular joints, and both size and environment effects are also considered. Further, fatigue tests are performed to study the fatigue strength of load-carrying and non-load-carrying steel cruciform joints that represent typical joint types in marine structures. The experimental results are then compared against ABS fatigue assessment methods, based on nominal stress approach, which demonstrates a need for better fatigue evaluation parameter. A good fatigue parameter by definition should be consistent and should correlate the S-N data well. The equivalent structural stress parameter is introduced to investigate the fatigue behavior of welded joints using the traction based structural stress approach on finite element models of specimens, and representing the data as a single Master S-N curve.