PSI - Issue 60

Dhanesh N. et al. / Procedia Structural Integrity 60 (2024) 456–470 Dhanesh et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig.14. Contour plot of accumulated strain limit damage in the dented pipeline.

5.3. Protection against Collapse from Buckling Elastic-plastic collapse analysis is performed till the factored external pressure load due to the embankment loads and the critical vehicular loads are applied to check the safety against buckling. As per Table 2D.4 of API 579 1/ASME FFS-1(2021), the external pressure generating loads (gravity and vehicular loads) are increased by a factor of 1.944. Fig. 15 shows the variation of relative vertical displacement between the peak dented location and casing start point with the load factor. The solution converges smoothly for the entire range of analysis and is safe against collapse from buckling.

Fig.15. Load factor Vs relative vertical displacement at the dented location.

5.4. Protection against Failure from cyclic loading (Fatigue) In the present case, the pipeline undergoes cyclic loading due to internal pressure variation and vehicular movement over the embankment. Hence analysis is carried out separately for these load cases to evaluate the cumulative fatigue damage. To evaluate the effect of vehicular loads, analysis has been performed with IRC recommended fatigue truck load (Refer to section 3.4.3). The maximum stress range due to fatigue truck load is 10 MPa, which is less than the endurance limit (Appx. 48 MPa) for the material. Hence the fatigue damage effect due to vehicular loads can be neglected.