낙하체 충돌을 고려한 심해저 매니폴드 보호 구조물 설계

Abstract

Subsea structures are always subjected to accidental risks induced by fishing gears, dropped objects, etc. This paper presents a design of the subsea manifold protective structure against dropped object impacts. Probable dropped object scenarios were established considering the shapes and masses of the dropped objects. Design layout of the manifold protective structure was proposed with the detailed scantlings and material specifications. A method applicable to the pipelinesspecified in DNV-RP-F107(DNV, 2010) was applied to calculate the annual probabilities of the dropped objects hitting the subsea manifold. The nonlinear finite element analyses provided the structural consequences due to the dropped object impacts such as the maximum deflections of the protective structure and the local fracture occurrences. A user-subroutine to implement the three-dimensional fracture strain surface was used to judge whether local fractures occurs. The proposed protective structure was proved to withstand the dropped object impact loads in terms of the maximum deflections even though the local fractures can induce accelerated corrosion.