Transportation Analysis

TRANSPORTATION ANALYSIS OF STEEL JACKET SUBSTRUCTURE USING

MOSES SOFTWARE

NORHAMIMI BINTI MOHD HANAFIAH

A report submitted in partial fulfillment of the

requirements for the award of the degree of

Bachelor of Civil Engineering

Faculty of Civil Engineering

Universiti Teknologi Malaysia

MEI 2009

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ABSTRACT

For many years, offshore structure has been transported on flat topped of barge-

launched type or on its own buoyancy from fabrication yard to offshore installation site.

The final year project emphasises on the transportation analysis of steel jacket

substructure using MOSES software. The result of analysis will give a better insight in

regard to the motion stability of the jacket and the transportation barge. The process of

transporting the jacket by barge need to be evaluated thoroughly by the design engineer

for the purpose of selecting the most economical transportation method. This can be

seamlessly done by considering the acceleration, motions, forces and moments during

the transportation. The barge selected for transportation procedure must be robust and

can greatly withstand the structure total weight as well as the environmental forces

experienced during voyage to installation site. The analysis is based on the actual data of

a project in Malaysia which the jacket is to be transported to the Malaysias oilfield.

MOSES, an acronym for Multi Operational Structural Engineering Simulator, is a

simulation and modelling language with great capability of motion analysis. The

software can be utilised to generate the result of motions, forces and moments of the

jacket members placed on the selected barge due to wave, wind and current effects. The

analysis procedure covers two barges which is the required standard dimension of barge

and an alternative barge as a comparison. The selection of the alternative barge will be

done using trial and error method as for optimization purpose. The selected barge will be

deployed for the jacket transportation as the analysis result satisfies the required

compatibility, limit state condition as well as safety aspects throughout the journey.

ABSTRAK

Selama beberapa tahun, struktur luar pantai telah diangkut di atas barj

permukaan rata jenis peluncuran atau dengan apungannya sendiri dari tempat pembuatan

ke tapak pemasangan luar pantai. Projek tahun akhir ini merangkumi analisis

pengangkutan substruktur jaket besi menggunakan perisian MOSES. Hasil analisis ini

akan memberikan pemahaman yang lebih baik berdasarkan kestabilan pergerakan jaket

dan barj. Proses pengangkutan jaket menggunakan barj perlu dinilai dengan teliti oleh

Jurutera Rekabentuk bagi tujuan memilih kaedah pengangkutan yang paling ekonomik.

Ini boleh dijalankan secara tersusun dengan mempertimbangkan pecutan, gerakan, daya

dan momen semasa proses pengangkutan. Barj yang dipilih untuk prosedur analisis

pengakutan ini haruslah boleh menanggung berat keseluruhan struktur termasuklah daya

persekitaran yang dihadapi semasa pelayaran ke tapak pemasangan. Analisis ini adalah

berdasarkan data sebenar satu projek di Malaysia dimana jaket itu akan diangkut ke

lapangan minyak di Malaysia. MOSES adalah akronim bagi Simulator Pelbagai Operasi

Kejuruteraan Struktur dimana ia menggunakan bahasa simulasi dan permodelan dengan

keupayaan yang tinggi untuk analisis gerakan. Perisian ini boleh digunakan untuk

menghasilkan keputusan bagi pergerakan, daya dan momen yang dihasilkan oleh

anggota jaket yang diletakkan di atas barj yang dipilih berdasarkan keadaan ombak,

angin dan keadaan semasa. Prosedur analisis merangkumi dua barj yang mana satu

daripadanya adalah mengikut dimensi standard barj manakala satu lagi sebagai barj

alternatif bagi tujuan perbandingan. Pemilihan barj alternatif akan dilakukan dengan

cara cuba jaya bagi tujuan pengoptimisan. Barj yang dipilih akan digunakan untuk

pengangkutan jaket kerana keputusan analisis telah memenuhi keperluan kesesuaian,

keadaan had limit dan termasuklah aspek keselamatan sepanjang perjalanan.

TABLE OF CONTENT

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ABSTRACT iv

ABSTRAK v

TABLE OF CONTENT vi

LIST OF TABLES xi

LIST OF FIGURES xiii

LIST OF ABBREVIATIONS xiv

LIST OF SYMBOLS xv

LIST OF APPENDICES xvi

1 INTRODUCTION

1.1 Introduction 1

1.2 Problem Statement 2

1.3 Objectives 3

1.4 Scope of Study 4

1.5 Significance of Study 5

2 LITERATURE REVIEW

2.1 Introduction 6

2.2 General Informartion 8

2.2.1 Sea State Criteria 8

2.2.2 MOSES Sign Convention, Coordinate System, Units

9

2.2.3 Sign Convention 9

2.3 Environmental Criteria 12

2.3.1 Basic Considerations 12

2.3.2 Risk Levels 12

2.3.3 Reduced Criteria 13

2.3.4 Practical Application 14

2.3.5 Long Transportation 15

2.3.6 Statistical Reservations 16

2.4 Motion Criteria 17

2.4.1 Empirical Approach 17

2.4.2 Analytical Methods 18

2.4.2.1 Design Storm 18

2.5 Motion Responses 19

2.5.1 Periods 19

2.5.2 Motions Response on Computer Programs 20

2.6 Strength Criteria 21

2.6.1 Loadings 21

2.6.2 Overhang 22

2.6.3 Fatigue 22

2.6.4 Seafastening 22

2.6.5 Cribbing 23

2.7 Stability 23

2.7.1 Intact Stability 23

2.7.1.1 Wind Overtuning 24

2.7.1.2 Wind Velocity 24

2.7.1.3 Angle of Downflooding 24

2.7.2 Damage Stability 25

2.7.2.1 Range of stability 25

2.7.2.2 Wind Overtuning 25

2.7.2.3 Wind Velocity 25

3 METHODOLOGY

3.1 Introduction 26

3.2 Barge Selection 27

3.3 Computer Modelling 28

3.3.1 Modifications 28

3.3.2 Boundary Condition 29

3.3.3 Design Criteria for Transportation 30

3.3.4 Other Consideration 31

3.4 Loads 31

3.4.1 Basic Load Cases 32

3.5 Transportation Analysis 33

3.5.1 Weight Grown Factors 33

3.5.2 Design Load Factors 34

3.5.3 Load Combinations 34

3.6 Hydrostatic and Stability Computations 36

3.6.1 Tow Condition 36

3.6.2 Stability Assessment 36

3.6.3 Intact Stability 37

3.6.4 Damage Stability 38

3.7 MOSES Output 40

3.7.1 Motion, force and Moment 40

3.7.2 Summary of Single Amplitude Motion 40

3.7.3 Summary of Single Amplitude Forces and Moments

40

3.7.4 Summary of Acceleration 40

3.7.5 Flow Chart of Work Procedures 41

4 RESULTS AND DISCUSSIONS

4.1 Introduction 42

4.2 Barge Selection Result 42

4.3 Barge Information 45

4.3.1 Standard Barge 45

4.3.2 Alternative Barge 46

4.4 Payloads Data 47

4.4.1 Substructure 47

4.5 Radii of Gyration and Windage Area for Substructure 48

4.5.1 Accordance to Standard Barge 48

4.5.2 Accordance to Alternative Barge 49

4.6 Hydrostatic and Stability Computations 50

4.6.1 Tow Condition 50

4.6.1.1 Substructure on Standard barge 50

4.6.1.2 Substructure on Alternative Barge 50

4.7 Tow Condition Summary 51

4.7.1 Tow Condition of Substructure on Standard Barge

51

4.7.2 Tow Condition of Substructure on Alternative Barge

52

4.8 Summary of Hydrostatic and Stability Analysis 53


4.8.1.1 Intact Stability Check 53

4.8.1.2 Damage Stability Check 54


4.8.2.1 Intact Stability Check 55

4.8.2.2 Damage Stability Check 56

4.9 Motion Output 57

4.9.1 Motion, Force and Moment 57

4.9.2 Summary of Single Amplitude Motion 58

4.9.2.1 Accordance to Standard Barge 58

4.9.2.2 Accordance to Alternative Barge 59

4.9.3 Summary of Single Amplitude Forces and Moments 60



4.9.4 Summary of Acceleration 62



4.10 MOSES Output 64



5 CONCLUSIONS

5.1 Introduction 88

5.2 Conclusion 89

5.3 Recommendation for Future Research 91

REFERENCES 92

APPENDICES 94

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Tows from Peninsular Malaysia to Sabah waters for 1-year Return period

8

3.1 Towing Metocean Criteria 30

3.2 Transportation Analysis Basic Load Cases 32

3.3 Weight Growth Factors 33

3.4 LRFD Load Factors 34

3.5 Load combinations 35

4.1 Dimension and result of selected barges 43

4.2 Result of towing condition 44

4.3 Particulars of Standard barge 45

4.4 Particulars of Alternative barge 46

4.5 Ballast pattern of Standard barge 50

4.6 Ballast pattern of Alternative barge 51

4.7 Summary of single amplitude motion on Standard barge 58

4.8 Summary of single amplitude motion on Alternative barge 59

4.9 Summary of single amplitude forces and moments on Standard barge

60

4.10 Summary of single amplitude forces and moments on Alternative barge

61

4.11 Summary of acceleration on Standard barge 62

4.12 Summary of acceleration on Alternative barge 63

5.1 Dimension of selected barges 89

5.2 Result of ballast pattern of selected barges 90

LIST OF FIGURE

FIGURE NO. TITLE PAGE

2.1 Barge Coordinate System 11

LIST OF ABBREVIATIONS

MOSES - Multi Operational Structural Engineering Simulator

API-RP2A - American Petroleum Institute

ISSC - International Ship Structure Congress

SES - Standard Engineering Specifications

SACS - Structural Analysis Computer System

COG - Centre of Gravity

LIST OF SYMBOLS

+ve - Positive

-ve - Negative

% - Percent

- Inch

TP - Peak Period

G - Gravity

- Degree

- Heel Angle

LIST OF APPENDICES

APPENDIX TITLE PAGE

A User Interface before run the software (input) 94

B User Interface after run the software (output) 96

C AutoCAD Modelling 98

CHAPTER 1

INTRODUCTION

1.1 Introduction

Offshore structures used for oil and gas extraction have the common function of

providing a safe, dry working environment for the equipment and personnel who operate

the platform (Yahaya, 2008). The traditional offshore installation shown an utilises a

welded steel, tubular framework jacket to support the topside facilities. The single

jacket installation is typical of the rig found in deep water environment. An offshore

structure installation usually consists of four project phases which is loadout,

seafastening, offshore transportation and installation (Yahaya, 2008).

Offshore transportation phase will comprises the tow to the location offshore and

the analysis to confirm the resistance of the structure and the barge toward the related

load like acceleration, motions, forces and moments during the transportation as well as

the ballast for positioning procedure. Transportation analysis will be done after the steel

jacket placed on the barge and be start towing to the oilfield by considering the sea-state

criteria and related environmental load (Chakabarti, 1994).

Tubular steel jackets are completely fabricated onshore prior to transportation to

site by dumb barge. The smaller jackets may be lifted in place by a floating crane whilst

the larger jackets may employ floatation devices to assist in their installation once

launched from the barge (Mather, 2000). The floatation devices are sequentially flooded

to enable the jacket to sink slowly into its final resting place. Once located on the

seabed the jackets are normally secured by foundation piles.

Transportation analysis is one of an important phase to be done during analysis

process as one step closer to installation process (Guy, Clifford, 1980). These analysis

need to be undertaken to calculate acceleration, motions, forces and moments faced by

the structure and the barge during transportation. All the values were used to determine

whether the barge selected were able to retain the structure total lift weight during the

transportation.

1.2 Problem Statement

To choose the right size of barge is very important depend on the size of the

structure since there is a variety size of barge in the region. If the barge selected is too

big the structure for sure is safe for the transportation but in is not sustain in term of its

cost. The barge selected has to be sure can resist the structure total weight with the

environmental force faced during the transportation.

In order to minimize the associated risk and secure safe transportation from the

fabrication yard to the offshore site, it is important to plan the transportation operation

carefully by considering the aspect required by the procedure. There is also some

guideline from API-RP2A that should be considered like previous experience along the

tow route, seasonal weather system and also appropriate return period for determining

design wind, wave and current condition, characteristic of the tow such as size, structure,

sensitivity and cost.

With the ballast value required known to obtain the required degree of pitch,

towing procedure will run smoothly. If the ballast analysis is not taken during analysis

stage, the structure may be failed during positioning stage and the barge will have a risk

of overturning.

1.3 Objectives

The objective of the transportation analysis is to demonstrate whether the

structure can resist the forces induced by the motions of the combined structure and

barge system without exceeding the allowable stresses. The analysis was carried out to

achieve following specific objectives:

1. To select the most economical and sustainable barge to transport the jacket

compared to required dimension of barge.

2. To calculate the ballast value based on tow condition.

3. To determine hydrostatic and stability value for towing condition.

4. To determine the acceleration, motions, forces and moments during

transportation by considering environmental load.

1.4 Scope of Study

The scope of the research will be focus on the outcome of the analysis using

marine software program MOSES. MOSES software will be used in designing and

analysis process. MOSES, an acronym for Multi Operational Structural Engineering

Simulator, is a simulation and modelling language. The analysis is based on the actual

data of a project in Malaysia which the jacket is to be transported to the Malaysias

oilfield. Motions, forces and moments are derived using ISSC spectrum using

specification sea state of 6.20 m (20.34 ft) significant wave height and mean period of

12.20 sec. These represent the tow condition for Sabah/Sarawak summer tow. The

result will be run on a selected barge and a barge with requirement size (SES 10.1). No

seafastening will be considered in the computer model as a preparation for worst case

scenario.

The motion forces and moments were generated using MOSES. These forces

and moments, coupled with the corresponding motion accelerations. A full motion

analysis of the barge was performed with results of maximum barge responses, payload

forces and moments obtained for beam (90o), quartering (135

o) and head (180

o) seas.

The analysis will be undertaken at ProEight Offshore Engineering Sdn. Bhd.

with supervision by Design Engineers as a collaboration project with MMC Oil and Gas

Engineering Sdn. Bhd. Guidelines for the transportation have been made with

referenced to Sarawak Shell Berhad Standard Engineering Specification on

Transportation of Substructure and Platform Components and General Transport.

1.5 Significance of Study

The research will show a result of transportation analysis using MOSES software

and the result is commonly used to make an analysis for offshore structure transportation

and as a preliminary study for installation phase. The result will show the compatibility

of the selected barge with the structure based on the acceleration, motions, forces and

moments as the outcome of MOSES.

This research summarized analyses undertaken for the generation of motion

accelerations and forces due to the transportation of steel jacket substructure. The

structure is to be transported to the existing oilfield in Sarawak.

The selection of the transportation barges were based on the feasibility studies

done earlier before running the transportation analysis. The resultant centre of rotation

and relative centre of gravity, as well as the location of the substructure will be shown in

a drawing that will be included in this research report.

Transportation Analysis

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