The safety of pipelines and subsea structures are key elements in subsea field developments. As part of the safety engineering, protection from dropped objects and third party impact actions is required. This article addresses this aspect. The combined response from global deflection and denting of pipelines subjected to impacts is investigated. Analysis and testing methods applied in pipeline design are presented. Focus is placed on the overall interaction between the impacting object, the deformed pipeline and energy dissipation by soil.
Typically, pipeline damage from design codes provides conservative cross sectional damage estimates. This is confirmed from both simplified and detailed FE analyses, as well as impact experiments performed by REINERTSEN AS.
One of the main objectives promoted by the authors is the importance of impact velocity and mass during impact, and not only the kinetic energy of the impact. The kinetic energy from a dropped object is unlikely to be fully dissipated as cross sectional deformation of the pipeline. Global deformations will be triggered, which implies that the dissipated energy going into local denting is reduced to a fractional value. This paper discusses the impact mechanics and seeks to estimate the fractional value by using simplified element analysis.