Proposed Joint Industry Project-

ULTIMATE STRENGTH LIMIT STATE CRITERIA

for SHIP-SHAPE FPSO NEW-BUILDS & CONVERSIONS

and SHUTTLE TANKERS

by

Dr Paul A Frieze

PhD, CEng, FRINA, MIStructE, MSNAME, ACIArb

PAFA Consulting EngineersHofer House

185 Uxbridge RoadHampton MiddlesexTW12 1BN UK

INTRODUCTION

1. ISO/TC 8/SC 8 Ship Structures has just voted affirmatively on a New Work

Item to develop an ISO Standard on Guidelines for the Ultimate Strength Limit State

(ULS) Assessment of Tankers, Bulkers, and related ship structures.

2. The strength formulations will apply to ship structure components plus the

hull girder and will allow for the effects of corrosion, fatigue cracking and damage due

to accidents. They will not deal with other relevant limit states such a fatigue and

serviceability.

3. The Standard will address the common forms of overall and local loading,

namely, wave bending and still water loads, bow and bottom slamming, greenwater,

cargo, thermal and sloshing. It will also address finite element modelling issues.

INTRODUCTION - II

1. The Project Leader is Professor Jeom Paik, Pusan National University,

Korea, who also prepared the proposal. Professor Paik is the author of a recent book

on Ultimate Limit State Design of Steel Plated Structures.

2. Professor Paik will prepare most of the draft on the strength formulations

and will draw heavily on his book for this. He has set himself a target of six months to

complete the first draft.

3. Professor Paik has requested PAFA Consulting Engineers to assist in

drawing up the requirements for slamming, greenwater and sloshing based on PAFA’s

work for UK HSE and its involvement in SafeFlow.

INTRODUCTION - III

1. Currently, ISO Standard 19904, Floating Structures for Petroleum & Natural

Gas Industries, is being finalised, under the auspices of ISO/TC 67/SC 7/WG 5, by an

Editing Panel (Bob Wolfram, Andrea Mangiavacchi & Paul Frieze) and is scheduled

for issue as a Draft International Standard (DIS) in September 2003.

2. ISO 19904 deals with FPSOs (includes FPSs, FSUs, etc), spars, TLPs and

semi-submersibles. It assumes Class Rules are used for sizing FPSO scantlings.

3. ISO 19904 should be in a limit state format but cannot be, in full, because

of, generally, the Working Stress Design basis of Class Rules.

4. Class Rules cannot deal readily with damaged or corroded ship structures

and thus are not generally suitable for application in the case of Conversions.

JIP OBJECTIVES

1. To develop ISO Standard Guidelines for the Ultimate Strength Limit State

Assessment of a) FPSOs and b) Shuttle Tankers.

2. For b) Shuttle Tankers, to achieve this by actively participating in the

ISO/TC 8/SC 8 Work Group on ISO Standard Guidelines for the Ultimate Strength

Limit State Assessment of Tankers, Bulkers, and related ship structures to include:

i) loadings due to greenwater, wave slam and sloshing,

ii) derivation of load and resistance factors

JIP OBJECTIVES - II

and introducing requirements peculiar to shuttle tankers, eg,

iii) normal loadings due to hawser and/or flexible hose connections to

FPSOs, dynamic positioning, or other arising from interactions with FPSOs

during offloading and related activities

iv) potential accidental loadings peculiar to shuttle tanker/FPSO

operations.

JIP OBJECTIVES - III

3. For a) FPSOs, to achieve this by (re)activating the ISO/TC 67/SC 7/WG 5

Panel on Structural Strength and including:

i) normal loadings peculiar to FPSOs such as a basic 100-year return

period design event and consistent side structure and transverse structure

events, effect of prolonged ‘head to seas’ exposure, heavy and concentrated

topsides loads and/or restraints, offloading, and connections to shuttle tankers.

ii) potential accidental loadings peculiar to shuttle tanker/FPSO

operations.

JIP OBJECTIVES - IV

iii) components peculiar to FPSOs such as turrets

iv) achieving compatibility/consistency with the requirements of ISO 19904 Floating Structures

v) derivation of the load and resistance factors, of which the latter may differ depending on whether they relate to New Builds or Conversions.

SCHEDULE & COSTS

The support effort for the workings of ISO/TC 8/SC 8 and the parallel complementary

work on shuttle tankers needs to put in motion shortly in order to comply with the

timetable set by ISO/TC 8/SC 8. The major effort on this should be completed this

year.

A preliminary estimate for the cost of this phase is £30,000 $48,000.

The significantly more intensive effort required to adapt the Guidelines to FPSO New

Builds and Conversions will take place in 2004 and is expected to cost some £125,00

$200,000.

DELIVERABLES

The prime Deliverable will be an ISO Standard on Guidelines for the Ultimate

Strength Limit State Assessment of FPSO New Builds & Conversions that:

a) deals with all standard ship structure components as well as the hull girder

plus those components peculiar to FPSOs such as turrets

b) allows for the effects of corrosion, fatigue cracking and accidental damage.

c) accounts for normal ship overall and local loadings but set in a 100-year

return period framework plus loadings peculiar to FPSOs (head to seas, heavy

concentrated topsides, shuttle tanker interactions)

DELIVERABLES - II

FPSO New Builds & Conversions Standard (cont.)

d) identifies relevant accidental loads (shuttle tankers)

e) addresses finite element modelling issues

f) specifies appropriate load and resistance factors differentiating between New

Builds & Conversions as necessary.

DELIVERABLES - III

The secondary Deliverable will be an ISO Standard on Guidelines for the Ultimate

Strength Limit State Assessment of (Shuttle) Tankers, Bulkers, and related ship

structures that deals with standard ship structure components and hull girders and their

loadings as well as:

g) addresses normal and accidental loadings due to shuttle tanker/FPSO

interactions

h) provides partial load and resistance factors relevant for shuttle tankers.

BENEFITS OF PARTICIPATION

The ISO Standard Guidelines will provide hull girder and component (including side and transverse structure) strength formulations that are:

* In a ULS format

* Account for typical aging and accidental damage

* Applicable to FPSOs- 100-year return period events, head to seas, heavy/concentrated topsides loads, wave slam, greenwater, sloshing, offloading, connections to shuttle tankers- accidental loadings peculiar to shuttle tanker/FPSO operations- both New Builds and Conversions

BENEFITS OF PARTICIPATION - II

* Applicable to shuttle tankers- relevant loadings as above- loadings due to hawser and/or flexible hose connections to FPSOs, dynamic positioning, other interactions during offloading - accidental loadings peculiar to shuttle tanker/FPSO operations

* Load and resistance factors appropriate to FPSOs & shuttle tankers

* Independent of class rules

* Consistent and compatible with the safety format and levels in ISO Standard 19904 Floating Structures for Petroleum & Natural Gas Industries.

NEXT STAGE

A Preliminary Draft of the Proposal has already been issued to a limited number of

potentially interested parties for their views and comments. Most of these have now

been received.

The Proposal will be revised to take account of these and and any further comments

/views that might be expressed here today or following this meeting.

The revised Proposal will be formally issued.