Fatigue strength assessments with two types of load carrying fillet weldment under out-of-plane bending load have been carried out by using both hot spot stress and structural stress methods. Basis for the derivation of structural stress method is discussed in detail. Finite element analyses using shell elements models have been performed for the fatigue strength assessment of weldments. As a result of the fatigue strength evaluation for load carrying transverse fillet weldment, hot spot stress method is found to be consistent with structural stress method as well as measurement. Hot spot stress, however, estimated for the load carrying longitudinal fillet weldment exhibit large variation with respect to mesh size and element type while the calculated structural stress for the longitudinal fillet weldment is relatively independent of mesh size. The fatigue life estimation according to structural stress has been introduced with the master S-N curve.

Two types of load carrying fillet weldment, which are typical weld joints in ship structures, were examined under out-of-plane bending load by using structural stress approach. Finite element analyses using both solid and shell elements models have been performed for the assessment of fatigue strength. Basis for the derivation of structural stress method is discussed in detail. The calculated structural stress values for the fatigue strength evaluation of load carrying fillet weldments are independent of mesh size. In this study, drawbacks and doubts associated with applying the structural method such as the guidance of virtual node method and the application of three-dimensional equilibrium condition for solid model have been discussed accompanied by various case studies. In order to solve the problem of the solid model, the alternative method for solid model by using the equilibrium condition of the nodal force has been introduced.

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