Effect of Bend Angle on Limit Loads of Pipe Bends under Internal Pressure and In-Plane Bending

Abstract

Abstract A pipe bend’s cross-section tends to deform significantly both in and out of its plane. This shell-type behavior, characteristic of pipe bends and mainly due to their curved geometry, accounts for their greater flexibility.

This added flexibility is also accompanied by stresses and strains that are much higher than those present in a straight pipe of the same size and material, under the same loading conditions. For this reason, pipe bends are considered the critical components of a piping system. Hence, for the purpose of designing and/or qualifying a pipeline structurally, it is useful to have a reliable estimate of their load-carrying capacity, along with a deep understanding of their structural behavior until instability, under different and combined loading conditions.

This research focuses on analyzing and solving a certain case of study of pipe bends presented in a Canadian research centre (Pipeline Integrity & Operations C-FERTechnologies, Edmonton, AB Canada). A horizontal water pipeline network of (1906 Km) made of carbon steel above ground. After the operation of the pipeline, a sudden ground settlement of one of the pipeline supports resulted in crack initiation then crack propagation that lead to the rupture of one of the connecting vital pipe bends and leakage. This ground settlement resulted in the displacement of one of the supports subjecting the pressurized pipe bend to in-plane bending moments in different directions that were expected to lead to that collapse.