The manufacturing method (seamless, UO, UOE) has a considerable influence on the collapse pressure of steel pipes. For UOE manufactured pipe, a significant reduction in collapse strength has been observed compared to not expanded pipe. A research program has been carried out to investigate the efffect of the manufacturing process on the collapse and local buckling behaviour. The results of collapse tests on three 20-inch UOE manufactured pipes and one seamless pipe are presented. The D/t ratios were 45, 27, 22 and 29. The paper also contains the results of finite element calculations, carried out to obtain more information on the parameters governing the collapse resistance of UOE manufactured pipes. The influence of the Bauschinger effect on the collapse resistance was determined. The results of probabilistic calculations with relevant experimental data related to collapse of pipes have been collected in a database and compared with the available design formulae. Design formulations for collapse with appropriate safety factors, calibrated against experimental and numerical models using probahilistic methods, have been selected for the practical range of design situations.
In the past 20 years, much research has been conducted into buckling and collapse of pipelines under external pressure, bending or tension and combinations. The available test results show considerable scatter, which is considered to be caused by variations in the stress-strain relationship, the anisotropy of the steel, the Bauschinger effect, the geometrical deviations, the residual stresses, the test conditions, etc. The manufacturing method (seamless, UO, UOE) has a considerable influence on these properties and on the collapse and local buckling resistance. For UOE manufactured pipe, a significant reduction in collapse strength has been observed compared to not expanded pipe. UOE manufactured pipe is often used for offshore pipelines. However, the number of tests carried out on such pipe was rather limited.
