Experimental investigation of pressurized steel pipes with mechanical defect under axial compression

Abstract In addition to the operational and environmental loads, an offshore pipeline may be subjected to accidental transverse loads by falling heavy objects or trawl gears. As a result, the load bearing capacity of the pipeline may be significantly impared by the dents, gouges or other types of damages caused by the impact. Such damage to an offshore structure may have serious environmental and economic consequences. In this study, results of experimental investigations on the residual strength of plain and gouged dented steel pressurized pipes under monotonic axial compression are presented. Some series small-scale specimens were fabricated from API-5L-X80 steel pipes with (D/t) ratio of 22 for the purpose of experimental tests. The specimens were dented by a spherical indenter with (d/D) ratio of 0.45 and gouges were applied along the pipe axis on the outer surface of the middle portion, whose cross section was rectangular. Defected and intact specimens were then collapsed by monotonic axial compression loading whilst subjected to constant internal pressure. In this research, effects of some key non-dimensional parameters such as dent depth, presence of the internal pressure and geometrical parameters of gouges have been studied.