DYNAMIC RESPONSE AND DAMAGE ASSESSMENT OF SUBSEA PIPELINES UNDER DROPPED OBJECT IMPACTS

Subsea pipelines transporting crude oil, liquified natural gas and carbon dioxide have been installed offshore for the past decades. However, there are many situations where heavy objects may drop from significant heights over subsea pipelines. These scenarios typically happen during crane operations on platforms, lifting operations from supply vessels, and accidental structural component failure. Such accidents can pose a significant threat to subsea pipelines due to the large mass and velocity of the dropped objects. Therefore, proper analysis and design shall be performed for subsea pipelines under accidental dropped objects impacts. However, present guidelines for the analysis and design of subsea pipelines subjected to dropped object impacts are limited and often based on simplified assumptions. The interaction of the dropped object and the impacted pipeline is often disregarded. In this study, dynamic analyses of subsea pipelines under dropped shipping containers are performed. Finite element models of steel pipelines with and without concrete coating were developed. The structural deformation and damage to both the dropped container and the impacted pipeline are considered. Numerical simulations were performed to investigate the effect of impact angle and pipeline dimensions. The contribution of concrete coating to impact resistance is also discussed. Design considerations were also proposed for dropped object protection of subsea pipelines based on numerical results.