Pipeline Strain-Based Design Approach: FEM Through Full-Scale Bending Tests

Fonzo, Andrea (Structural Integrity Department, Centro Sviluppo Materiali SpA) | Ferino, Jan (Structural Integrity Department, Centro Sviluppo Materiali SpA) | Spinelli, Carlo Maria (INVTEC Department, Technology Planning, ENI Gas & Power)



The need to study the strain-based pipeline behaviour subjected to bending and pressure pushed the development of an improved full-scale facility as pre-requisite for undertaking realistic tests. The experimental activities in several ENI‟s projects on very high strength steel pipes made available a consistent database for building a robust numerical model. This paper provides a description of CSM‟s testing device, specifically designed to test large diameter gas linepipe in plastic regime. The experimental data has been used for comparison with the results from a computational FE model able to predict pipeline buckling behaviour. This paper addresses the main key-points and results of this model.


The increasing gas demand, forecast after Fukushima event needs reliable and cheap transportation options to gather huge natural gas quantity from remote regions to the final market, as the closest ones are declining. In several occurrences a High Pressure transportation approach joined with the use of High Strength Steel (HSS) pipeline appears as the most convenient way to combine technical feasibility, cost effectiveness and reliability over the whole pipeline lifetime span. Crossing harsh areas involves complex hazards to be faced or anticipated. For on-shore pipelines, specifically, integrity may be a function of the geographical area, where additional external load action may be due to ground movement and must be considered since from the design stage and faced during operation and maintenance. In order to describe the pipe limit capacity under combined loading, accurate models are required. Depending on the area of application, significant strain demand due to different types of ground movement can take place, reflecting in specific requirements for line pipe material in terms of strain resistance capability. As a consequence a deeper understanding of the pipe strain capacity is a key point to be addressed.