Prediction of plastic deformation of post-buckling subsea pipelines

Subsea pipelines transport offshore petrochemical resources. Such pipelines undergo lateral global buckling deformations owing to the high temperatures and pressures during operation. The large lateral deformation generated in a lateral global buckling process causes the cross-section of the deformed pipeline to bend plastically, threatening the integrity of the pipeline system. The value of the plastic strain is a key index for assessing the safety of deep-sea pipelines. This study analysed the distribution and development of a plastic strain during a lateral global buckling process using the finite element method, highlighting the decisive role of the initial imperfection on the location of the plastic strain, and the impacts of three types of influential parameters on the value of the plastic strain. Based on a large number of simulation results, fitting equations were proposed for predicting the value of the plastic strain according to the values of the influential parameters. Validations of the fitting equations were also conducted; the relative deviation between the predicted value and finite element analysis results is less than ±8 % for predicting a typical compressive strain, and less than ±10 % for predicting a typical tensile strain.