PSI - Issue 57

Kashif Kamran Toor et al. / Procedia Structural Integrity 57 (2024) 772–784 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Where, SCF = any additional SCF, such as thickness effect Add.Fac = design safety factor on stress range 2.2. Hot Spots

Fatigue critical hot spots must be selected to evaluate the damage at the local joint. The global model does not include the local joint geometry, therefore a detailed local FE model of the joint is prepared to calculate the stress at the fatigue critical location denoted as hot spot. In the present analysis only one pile sleeve connection is included where the fatigue life at a hot spot, labelled as AT1029, is calculated. The global model and local FE model of the selected joint is shown in Fig. 4.

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b

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Fig. 4. (a) Global model; (b) Local FE model; (c) Hot spot location.

2.3. HSS Extrapolation The hot spot is located at the cope hole in the shear plate on the sleeve side and attached to the mid yoke plate. A local FE model of the joint was used to calculate the INF at the selected hot spot. The INF is the hot spot stress at a weld toe because the unit load application in the local element axis is the same as in the global analysis. The INF is in principle a stress-load relationship and the units are MPa/MN and MPa/MNm for force and moment response respectively. The hot spot stress is calculated using the general stress extrapolation at the weld toe location either on the plate surface (type ‘a’) or at the plate edge (type ‘b’) , Fig. 1. The following extrapolation methods are recommended for the two types: Type ‘a’ hot spots: Linear extrapolation of read out stress at two reference points located at 0.4t and 1.0t from the weld toe/singularity, IIW (2014). ℎ = 1.67 × 0.4 − 0.67 × 1.0 (3) Type ‘b’ hot spots: Quadratic extrapolation of read out stress at three reference points located at absolute distance of 4, 8 and 12 mm from the weld toe, DNV-RP-C203 (2016) and IIW (2014). ℎ =3× 4 −3× 8 + 12 (4)