Introduction

Subsea structures generally contain some equipment. This can be anything from from valves to umbilical termination units. If the structure contains equipment, then this is usually protected from objects dropped from the water surface by means of a roof panel.

The dropped objects considered can be anything from small hand tools (wrench) to large objects dropped from cranes. The design has to withstand the impacts from these objects, and energy methods are used in the design.

Typical loads from NORSOK U001:

It's worth noting that the force generated during the impact is used in the roof support design and foundation design.

Notable Projects

Project Name
Project Number
Notes
Wage Paladin
KW 694
CATS Tee Tie-In Structure
West DON & DON South West
KW 1009

Riser Base Structure
Gravity Based Foundation, Multiple Headers

Subsea Distribution Unit Protection Strucutre
Pile Foundations, 'Fishing Friendly' design

SSIV Protection Structure
Gravity Based Foundation

 

Codes & Standards

Company
Title
Doc Number / Date
NORSOK
Subsea Production Systems
U001

 

Books

Author
Title
Chapter

 

Related Subjects

Structural Global Analyses
Structural Appurtenances
Structural Foundations
Lifting
Weight Take Off

Dropped Objects

Return

roof

The roof is generally fabricated using steel grating similar to that used for walkways (shown below), which is supported with a frame structure.

As the grating is relatively flexible compared to the partent structure and supporting frame, plastic deformation in the bearing bars of the grating section absorbs the impact energy. This allows the rest of the structural members to remain elastic.

grating
test