Parameters affecting the behaviour of steel pipes under impact loading

Subsea steel pipes are often used to form extensive networks for transporting oil and gas over large distances. Such pipes can be subjected to actions characterised by high loading rates and intensities stemming from high-mass low-velocity collisions. To ensure that such networks continue to operate, even after being subjected to impact loads, it is essential that the behaviour of the pipes is characterised by a certain level of resilience. Considering that most of the available data obtained from drop-weight tests on steel pipe specimens does not provide a detailed description of the behaviour exhibited throughout the loading process, the work herein aims at investigating numerically, via dynamic nonlinear finite element analysis, the problem at hand. After validating the predictions obtained against the available test data, the numerical investigation focuses on studying the effect of a range of parameters on the exhibited behaviour. The latter parameters are associated with the shape and mass of the impacting object, the geometry and the support conditions of the pipe, the level of axial loading (applied along the axis of the pipe) as well as the level of internal and/or external pressures imposed onto the pipe walls. The numerical predictions reveal that the above parameters, most of which are associated with the insitu conditions imposed onto subsea pipes throughout their operational life, can influence, potentially detrimentally, the exhibited behaviour. The numerical predictions obtained reveal that this effect is not accurately captured by the existing assessment methods employed in practice for predicting the level of damage suffered by pipes during impact.