STRUCTURAL INTEGRITY OF WELDED TUBULAR JOINTS IN RANDOM LOAD FATIGUE COMBINED WITH SIZE EFFECT

The evaluation of the integrity of structural components involves defect assessment. This includes detection, sizing and fracture mechanics analysis for remaining fatigue life. Each of the above three areas still poses challenging problems for the offshore industry. This paper tackles some of the problems in the fatigue fracture mechanics analysis of welded tubular joints. Extensive constant amplitude fatigue testing on welded tubular joints has allowed the establishment of a fracture mechanics model, the Two Phase Model (TPM), which takes into account the size effect. This model is especially effective in predicting the remaining life of cracked tubular joints of any size. New data are now emerging from fatigue tests under broad band signals simulating the offshore environmental loading. Tests utilising this type of loading give better representation of the fatigue conditions encountered in the offshore environment. The results can also be used to validate the TPM modelling of size effect under these more complex load histories.