Low-velocity impact of pressurised pipelines

Experimental tests are reported on steel pipelines which have been struck by a relatively large rigid wedge-shaped mass travelling up to 10.4 m/s. A pipeline is supported across a span, is fully clamped at both ends and is struck at the mid-span and at the one-quarter span positions. Most of the pipelines are pressurised with a nitrogen gas. The initial impact energy produces large inelastic ductile deformations of the pipeline and, in some cases, failure. A method is introduced which idealises a deformed pipeline cross-section in order to estimate the local and global components of the total displacement from experimental measurements of the final cross-section. Comparisons are also made with several previously published experimental studies for which sufficient data are available to make the calculations. A clearer insight into pipeline behaviour is achieved than is possible only with values of the maximum permanent transverse displacements which have been reported in previous experimental studies. This information should assist with pipeline design, provide more rigorous validation for numerical schemes and contribute to a better understanding of pipeline failure. Recommendations are made on the accuracy and suitability of some well known empirical equations for predicting the permanent deformations of pressurised and empty pipelines caused by large rigid masses, relative to the pipeline mass, travelling with low initial impact velocities up to about 15 m/s.