Case Study of Different Calculation Method for Hot Spot Stresses at Ship Structural Detail

Fatigue analysis and estimation of safe life of structures that are subjected to cyclic loadings, such as ships and offshore structures is one of the most important steps of structural design. Fatigue failure in the form of crack will start from details and propagate in structure. In steel structures these cracks will started from welds. Most of the methods for fatigue life assessment in welded connections are based on stress values at critical points, called "hot spot". Determination of hot spot stress is done by finite element analysis with using some empirical relations, which is expected to be the most practical method. These empirical relations are mostly based on linearization of stress through the thickness or extrapolating the stress to the hot spot locations. In this paper, different methods are reviewed for the evaluation of hot spot stress at a typical ship structural detail by finite element analysis and the results are compared with an experimental data. Accuracy and sensitivity of hot spot stress to finite element meshing is investigated, and the best method for calculation of hot-spot stress based on required accuracy, time and money is proposed.