Cross-Flow Vortex Induced Vibration Fatigue Analysis of Persian South Gas Field Subsea Pipelines Due to Multi-Spanning


1 M.Sc. student of Petroleum University of technology, department of offshore engineering

2 Assistant- Prof. of civil Petroleum University of technology, department of offshore engineering


Free-span in subsea pipelines occur at manmade supports, uneven seabed or pipeline crossing. Free spanning may induce pipeline vibration due to vortex shedding which makes pipeline susceptible to some failures such as fatigue, fracture, etc. Free spanning analysis is an important subject because fatigue is the most effective factor in reducing the pipeline design life. Free spanning analysis includes static analysis and dynamic analysis.
DNV-RP-F105 suggests a methodology of dynamic analysis for long pipeline with multi-mode responses, but the fatigue analysis method for multi-modes is not detailed. In addition, the fatigue analysis of multi-spanning pipeline is not clear. Based on the methodology of DNV-RP-F105 fatigue life relates to natural frequencies of pipeline, the method of determination of effective natural frequencies still is not clear.
In this paper, a fatigue analysis for multi-spanning pipeline in Persian south gas field is performed based on VIV analysis. ABAQUS FE model is developed to obtain the stress distribution and the natural frequency of each vibration mode for spanning pipeline on seabed with three multi-spans, then the fatigue analysis of VIV is carried out for the spanning pipeline based on DNV-RP-F105.


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