Residual ultimate strength of seamless metallic pipelines with structural damage

This thesis deals with the structural damage and its corresponding effect on the residual ultimate strength of seamless metallic pipes. The structural damage is here characterized as the type of damage produced by external mechanical interference, considerably undermining the strength and/or stability of the pipes. Not only the aesthetic appearances of the pipes are affected by the occurrence of damage, but most importantly the pipes’ functional demands are jeopardized. This research project aims to develop an effective prediction model to predict the residual ultimate strength of damaged metallic pipes subjected to a bending moment. To be able to effectively predict the residual strength, the types of structural damage need to be first categorized and simplified. Three typical types of damage are deployed for the further quantification of the effects, including a dent, metal loss in terms of a notch, and a combined dent and notch on the compression side of pipes. Meanwhile, the damage in terms of a crack, a notch and the combined notch and crack on the tensile side of pipes is qualitatively investigated. Once it occurs, the fracture failure of pipes is likely to happen, which may introduce a detrimental consequence.