Mechanical Behavior of Steel Pipe Bends; An Overview.

An overview of the mechanical behavior of steel pipe (elbows) is offered, based on previously reported analytical solutions, numerical results and experimental data. The behavior of pipe bends is characterized by significant deformations and stresses, quite higher than the ones developed in straight pipes with the same cross-section. Under bending loading (in-plane and out-of-plane) the main feature of the response is cross-sectional ovalization, which influences bending capacity and is affected by the level of internal pressure. Bends subjected to cyclic in-plane bending exhibit fatigue damage, leading to base metal cracking at the elbow flank. Using advanced finite element tools, the response of pipe elbows in buried pipelines subjected to ground-induced actions is also addressed, with emphasis on soil-pipeline interaction. Finally, the efficiency of special-purpose finite elements for modelling pipes and elbows is briefly discussed.