VIVA VOCE NORZILA NOH 0008908 - 10122021.pptx

INPLACE ANALYSIS OF
RELOCATABLE PLATFORM FOR
MARGINAL FIELDS
OAV5213 – Research Project 1
For MSc Offshore Engineering, UTP
By NORZILA NOH (0008908)
Supervisor: Dr Montasir Osman Ahmed Ali
UNIVERSITI TEKNOLOGI PETRONAS
Department: Civil & Environmental Engineering
Program : Embassy of Offshore Engineering

PRESENTATION OUTLINES
2
Literature
Review
• Self-Installed
Relocatable
Platform
• Static Analysis
• Accidental Analysis
Scope of Study
Research
Objectives
Problem
Statement
Research
Background
• Marginal Fields
• Offshore Structures
• Relocatable
Platform

PRESENTATION OUTLINES
3
Conclusion &
Recommendations
Discussion
Results
Execution
Schedule
Methodology
• Software, Code &
Standards
• Research Data
• Member Properties
• In-place Analysis

RESEARCH BACKGROUND
1
4
• Marginal Fields
• Offshore Structures
• Relocatable Platform (Jack-up)

1-1. Marginal Fields
5
What
• Small reserve
• Short field life
Challenge
• Meet min. ROI
Target
• Cost Effective
Water Depth
• In Southeast
Asia, mostly
shallow water
Typical Fixed Piled Jacket
Structure

1-2. Offshore Structures
6
Structural
Concept
Environment
Water
Depth
Extraction
Method
Reservoir
Size
Cost
Effective
Short Life
FIXED
STRUCTURE
MOBILE/
FLOATING
STRUCTURE
?

1-3. Relocatable Platform – Jack-up
7
Transit
Install Elevated/
Operation
Self-elevated relocatable unit such as jack-up structure is
another alternative with credits on its mobility and reusability.

1-3. Relocatable Platform – Jack-up
8
a) Lattice Leg (Bracing leg)
Jack-up Structure
b) Tubular Leg (Bracing leg)
Jack-up Structure
Spud Can/
Suction Pile
Leg
Barge Deck
Jacking System

1-3. Relocatable Platform
9
Function Fixed Piled Jacket Jack-up Structure
Foundation Piles, foundation
bearing capacity
Suction pile, spud cans
Installation Barge transport,
launch, upend, piled
foundation
Tow to site – leg up.
Leg down, penetrate,
ballast, pile and
deballast,
Limitation Reusability, mobility Scouring, marine
growth cleaning,
utilization area
Advantage Stability, bigger
topside payload
Reusability, mobility,
smaller topside
payload
Fixed Piled
Jacket Platform
Relocatable
Platform Jack-up
Structure

2. Problem Statement
11
PETRONAS has identified
105 marginal oil fields in
Peninsular Malaysia (equiv.
580 million barrels of crude
oil / 30 million barrels for
each field).
The development
concept of a marginal
field critically needs to
consider COST
EFFECTIVE measures:
1. CAPEX Reduction
2. Rapid Deployment
3. Easy Removal

◦ A comparison of cost and schedule estimation for fixed and
jack-up structures for 30m water depth at Southern Sector
of North Sea had been made.
12
Fixed Jacket Structure (six-
legged)
Category Jack-up Structure (four-legged)
o Fabrication until before start
production > ₤31 million.
o Installation = ₤4.2 million.
o Hook-up = ₤3.2 million.
COST o Fabrication until before start
production > ₤31 million.
o Installation = ₤1 million.
o Hook-up = ₤0.5 million.
21 months SCHEDULE
(design until
equipment pre-
commissioned)
19 months (inclusive the duration
required for long lead equipment 12
months)

13
No Category Saving
1 FEED & Detail Design 43%
2 Refurbished Top Deck + 6 slot well manifold (400MT) 42%
3 Topside Facilities - include the following new items:
- Chemical Injection Skids (4 nos), Diesel Injection Skid (1 no),
MPFM (1 no)
- Instrument Panel / PLC Control System
- All other items refurbished
36%
4 New build jacket + anodes + boat landing (400MT) 0%
5 New & Reused Piles 42” x 4 nos (500MT) 26%
6 Transportation to site -98%
7 Installation, utilizing 800MT HLV
8 Commissioning
9 Project Management 11%
ESTIMATED TOTAL EPC COST SAVINGS 38%
Case Study for Reused of Topside for a Jacket Platform
The Proposed novel relocatable offshore platform:
◦ Will reduce the CAPEX
◦ Will reduce the decommissioning cost significantly compared to conventional platforms

14
Conventionally, installation of
jack-up requirement to use
heavy lift / tow barges and pile
driving hammers.
At remote area, it cause
higher cost and longer
schedule.
SELF-INSTALLED
RELOCATABLE
PLATFORM
- Using Suction Pile
1. CAPEX Reduction
2. Rapid Deployment
3. Easy Removal

3. Objectives
16
Study aim: To develop new concept of relocatable offshore
platform that can suit Malaysian waters.
To develop a numerical model for the relocatable platform using
commercial software.
To carry out in-place analysis by simulating the environmental
parameters in Malaysian waters.
To assess the stability of this relocatable platform in case of losing
critical member. Few structural members with highest stress will be
omitted to observe the impact of the jack-up structure.
1
2
3

◦ Proposed platform with four-legged lattice columns.
◦ Metocean parameters of multiple marginal oil fields within the
Malaysia’s shallow waters (maximum of 62m).
◦ In-place analysis of the structure under the hydrodynamic loadings
(consists of waves, wind and current).
◦ The foundation is idealized to be pinned support and soil-pile
interaction is excluded.
◦ Earthquake is not covered in this study.
◦ The topsides equipment and architectures are assumed to be
simplified as a single topside load at the center of the jack-up.
◦ Fatigue, other accident and pre-services analyses such as push over
analysis, transit analysis, lifting analysis are not covered in this study.
4. Scope of Study
18
Proposed Relocatable
Platform Jack-up
Structure

LITERATURE REVIEW
5
19
Literature
Review
Self-
Installed
Relocatable
Platform
Static
Analysis

(D.P. Tuturea – Conoco Inc, G.Jackson – Arup
Energy et al. 2002)
◦ A four-legged self-installing steel gravity
relocatable platform.
◦ A steel gravity or skirted base.
◦ The leg is designed to be connected at the
side of the barge deck.
5-1. Relocatable Platforms
20
Hang Tuah MOPU

(Nagendran C. Nadarajah, Renata Anita De Raj,
Mahendran Suppiah, et al 2011)
In 2010, a self-elevating mobile platform with:
◦ removable wellhead deck
◦ removable subsea conductor frame
◦ subsea conductor frame the jacket legs and
part of the foundation at the same time.
21
Suction-piled Stacked Frame
(SSF) platform

(Frank Slangen, Wim Bal and Mark Riemers et al 2011)
◦ 5 deck levels platform supported by 4 tubular unbraced legs, founded
on 4 huge suction piles.
◦ Connection decks is designed to allow sliding of the leg during
installation.
◦ Three conductors run through one of the 4 legs, whereby one well will
run through the inside of the suction pile.
22
FE-FA platform

(Borneo Seaoffshore, Brian Chang et al 2018)
◦ Mono-Column Platform (MCP) is a self-
elevating relocatable jack-up with single
column at the center supported with mat-
supported footing works for 120m water
depth.
◦ It has lighter version targeting shallow water
below 90m.
23
Mono-Column Platform

(P.A. Thomas, N. Tcherniguin, A. Maconochie and
J. Oliphant, TECHNIP et al 2007)
◦ Three-legged self-installed jack-up founded
on retractable suction piles.
◦ Retractable caisson within each leg.
◦ Associated with each caisson is a suction
pump facility.
24
Retractable Suction Pile
Jack-up Platform

(Sanam Aghmady et al 2008)
◦ Investigate the impacts of environmental loads on the total base shear
force and overturning moment, of real life jack-up structures using SACS
software and in-house computer program.
◦ Shear and overturning moment governed by wave forces.
◦ Increase member diameter improve base shear but low relative change
in the overturning moment.
5-2 Inplace Analysis
25

(E.T.R.Dean, R.G.James, A.N.Schofield, and Y
.Tsu Kamoto et al 1995)
◦ Simulation of 3 leg jack-up platform
subjected to horizontal load.
◦ Results shows the rotational stiffness of
spud can, leg length and leg flexural
rigidity can affect the of moment fixity.
◦ The fixity also degrades with increasing
horizontal load.
◦ Longer leg under high lateral load has
smaller fixity as compared to short leg
under low lateral loads .
5-2 Inplace Analysis
26

METHODOLOGY
6
27
• Software, Codes and Standards
• Research Data
• Member Properties
• In-place Analysis
Member
Properties
Software,
Code &
Standards
Research
Data
In-Place
Analysis
Finish
Fail
Success
Repeat

6-1 Software, Code and Standards
28
Commercial software
1. API RP2A-WSD 21st Edition
2. AISC-ASD 13th edition
3. SNAME (Society of Naval Architects and Marine
Engineers) - Guidelines for Site Specific Assessment of
Mobile Jack-Up Units.
4. DNV-OS-C104 - Structural Design of Self-Elevating
Units.
5. HSE-UK - Guidelines for Jack-Up Rigs with
Particular Reference to Foundation Integrity, MSL
Engineering.
6. ISO 19905-1/2012 – Site Specific Assessment of
Mobile Offshore Units – Part 1: Jack-ups
7. PTS 34.19.10.30, Design of Fixed Offshore
Structures
SOFTWARE CODE AND STANDARD

6-2 Research Data
29
◦ This design of this
relocatable platform is to
suit for benign and calm
condition based on few
areas in Malaysia namely
Erb West and Samarang
field.
◦ The environmental data
required to determine the
loads to this study as per
specified in Appendix L of
PTS 34.19.10.30, Design of
Fixed Offshore Structures
(Rev.7).

◦ Four-lattice legged founded on spud can.
◦ The platforms is expected to serve in 3 to
4 locations, which around 5 year at each
location, water depth 30-62m.
◦ Material grades and dimensions will be
further defined in next stages.
6-3. Member Properties
30
Platform Shape Square shaped
Platform Dimension 36m x 36m each square shaped
Number of Leg 4 legs
Leg dimension 4m x 4m each square shaped
Centre-to-centre Leg Spacing 30m
Leg Height 104m
Air Gap 12.5m
Topside Payload 2500MT
Foundation Spud can

◦ For extreme case, SNAME RP recommend to design based on 50-year extreme
environmental load but due to limitation of environmental information, writer is referring
Appendix L of PTS 34.19.10.30, Design of Fixed Offshore Structures for 100-year extreme
wave, wind, and current data.
◦ Static in-place analysis is performed by considering loading conditions:
1. Still Water Case for 1-Year Condition (Design Operating Condition)
2. 100-Year Condition (Design Extreme Condition).
◦ Design and strength of structures are expressed in Unity Checks (UC) <1.0.
◦ The pile soil interaction is neglected in this analysis. The bottom legs is pinned supports.
◦ For both operating and extreme conditions, eight wave headings to be considered.
◦ 1-minute sustained wind speed to be applied associated with the direction of wave
conditions.
◦ A one – third increase in basic allowable stresses was applied in accordance with API-
RP2A-WSD only for 100-years extreme condition.
6-4 In-place Analysis
31

◦ Hydrodynamic Coefficients (PTS 34.19.10.30):
◦ Marine Growth (PTS 34.19.10.30):
- dry unit weight of marine growth is 10kN/m3
- Based on the marine growth profiles, profile at East Peninsular
Malaysia is adopted for both Erb West and Samarang case
studies for better conservativeness.
6-4 In-place Analysis – Design Parameters
32

◦ Air Gap (SNAME and PTS 34.19.10.30):
▫ air gap is 1.5m above the maximum extreme wave height. In this
study, the seabed subsidence condition is excluded.
◦ Splash Zone (PTS 34.19.10.30):
▫ region in the range of +5.0m and -3.0m from the Mean Sea Level
(MSL).
◦ Corrosion Allowance (PTS 34.19.10.30):
1. 6mm of thickness for primary members such as legs and vertical
diagonal members and
2. 3mm for horizontal members.
6-4 In-place Analysis – Design Parameters
33

◦ the soil and foundation parameter are excluded, and the analysis is
simplified assuming a planar seabed.
◦ The topside load is assumed to be at the centre of the platform and
any COG envelope shifting required further detail study.
◦ Also considered only 1 level barge deck.
◦ The platform is expected to be connected conductor supported by
other structural framing, therefore any lateral loads from conductor
are not expected to be considered in this study. Helicopter deck or
crane are not to be incorporated in detail at this stage.
6.4 In-place Analysis – Simplification
34

6-4 Static In-place Analysis
35
Structural
Modelling
Member
Properties
Load Inputs
Seastate Inputs
• 1-year Operating
Condition
• 100-year Storm
Condition
In-place Analysis
Result Checking -
UC for member
and joint
Finish

◦ Gravity loads + live loads (factor 0.6) + environmental loads 8
directions.
6.4 In-place Analysis – Load Combination
36
Basic
Load
Case
Description
Load Combination Factors
OPERATING CONDITION STORM CONDITION
1001 1002 1003 1004 1005 1006 1007 1008 3001 3002 3003 3004 3005 3006 3007 3008
BBA Self-Generated Weight of the Structure 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
BBB Topside Payload (2500MT) 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
LLA Live Load (20kPa) 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60
OW+X Operating Wind in +X Direction (0o) 1.00 0.707 0.707 1.00
0.70
7
0.70
7
OW+Y Operating Wind in +Y Direction (90o) 0.707 1.00 0.707
0.70
7
1.00
0.70
7
OW-X Operating Wind in -X Direction (180o) 0.707 1.00 0.707
0.70
7
1.00
0.70
7
OW-Y Operating Wind in -Y Direction (270o) 0.707 1.00 0.707
0.70
7
1.00
0.70
7
SW+X Storm Wind in +X Direction (0o)
SW+Y Storm Wind in +Y Direction (90o)
SW-X Storm Wind in -X Direction (180o)
SW-Y Storm Wind in -Y Direction (270o)
201 Operating Wave and Current at Samarang in 0o 1.00
202
Operating Wave and Current at Samarang in
45o
1.00
203
90o
1.00
204
135o
1.00
205
180o
1.00
206
225o
1.00
207
270o
1.00
208
315o
1.00
401 Storm Wave and Current at Samarang in 0o 1.00

1. Member with maximum stress is identified from inplace analysis and
omitted to observe the impact to the whole structure.
2. The platform stability is assessed by removing the pinned fixity at one
of each leg to observe the effect globally – tested with Erb West.
6.4 Accidental Analysis
37

EXECUTION PLAN
Yellow
Is the color of gold,
butter and ripe
lemons. In the
spectrum of visible
light, yellow is found
between green and
orange.
Blue
Is the colour of the
clear sky and the
deep sea. It is
located between
violet and green on
the optical spectrum.
Red
Is the color of blood,
and because of this
it has historically
been associated with
sacrifice, danger and
courage.
39

8.1 Inplace Analysis – Load Tables (Erb West)
41
Basic
Load
Case
Description
Fx Fy Fz Mx My Mz
kN kN kN kNm kNm kNm
BBA Self-Generated Weight of the Structure 0 0 -26898 -511050 511050 0
BBB Topside Payload (2500MT) 0 0 -29188 -554572 554572 0
LLA Live Load (20kPa) 0 0 -27600 -524400 524400 0
OW+X Operating Wind in +X Direction (0o) 165 0 0 0 24846 -3129
OW+Y Operating Wind in +Y Direction (90o) 0 165 0 -24851 0 3141
OW-X Operating Wind in -X Direction (180o) -165 0 0 0 -24814 3156
OW-Y Operating Wind in -Y Direction (270o) 0 -165 0 24808 0 -3124
SW+X Storm Wind in +X Direction (0o) 695 0 0 0 101487 -13201
SW+Y Storm Wind in +Y Direction (90o) 0 695 0 -101491 0 13201
SW-X Storm Wind in -X Direction (180o) -695 0 0 0 -101489 13201
SW-Y Storm Wind in -Y Direction (270o) 0 -695 0 101489 0 -13201
101 Operating Wave and Current at Erb West in 0o 151 0 -10 -194 9154 -2864
102 Operating Wave & Current at Erb West in 45o 114 114 -9 -7343 7343 0
103 Operating Wave & Current at Erb West in 90o 0 151 -10 -9154 194 2864
104 Operating Wave & Current at Erb West in 135o -114 114 -9 -7367 -7041 4345
105 Operating Wave & Current at Erb West in 180o -151 0 -11 -204 -8756 2864
106 Operating Wave & Current at Erb West in 225o -114 -114 -9 7013 -7013 0
107 Operating Wave & Current at Erb West in 270o 0 -151 -11 8756 204 -2864
108 Operating Wave & Current at Erb West in 315o 114 -114 -9 7041 7367 -4345
301 Storm Wave and Current at Erb West in 0o 828 0 -5 -89 52624 -15725
302 Storm Wave and Current at Erb West in 45o 612 612 -31 -39682 39682 0
303 Storm Wave and Current at Erb West in 90o 0 828 -5 -52624 89 15725
304 Storm Wave and Current at Erb West in 135o -618 618 -15 -39541 -38984 23496
305 Storm Wave and Current at Erb West in 180o -827 0 -33 -626 -50788 15722
306 Storm Wave and Current at Erb West in 225o -617 -617 -21 38910 -38910 0
307 Storm Wave and Current at Erb West in 270o 0 -827 -33 50788 626 -15722
308 Storm Wave and Current at Erb West in 315o 618 -618 -15 38984 39541 -23496

8.1 Inplace Analysis – Load Tables (Erb West)
42
No
Combined
Load Case
Fx Fy Fz Mx My Mz
Operating Loads + 1-year Environmental Loads (Operating Condition)
1 1001 316 0 -72957 -1386369 1419978 -5993
2 1002 231 231 -72956 -1411088 1410888 8
3 1003 0 316 -72957 -1420180 1386173 6005
4 1004 -231 231 -72955 -1411111 1361394 8797
5 1005 -316 0 -72958 -1386378 1352409 6020
6 1006 -231 -231 -72956 -1361622 1361422 23
7 1007 0 -316 -72958 -1352611 1386182 -5987
8 1008 231 -231 -72955 -1361594 1410911 -8766
Operating Loads + 100-year Environmental Loads (Storm Condition)
1 3001 1522 0 -56392 -1071624 1225449 -28926
2 3002 1103 1103 -56418 -1182971 1182771 0
3 3003 0 1522 -56392 -1225649 1071427 28926
4 3004 -1110 1110 -56402 -1182830 960602 42162
5 3005 -1522 0 -56420 -1072160 919061 28923
6 3006 -1109 -1109 -56408 -960872 960676 0
7 3007 0 -1522 -56420 -919257 1071964 -28923
8 3008 1110 -1110 -56402 -960798 1182630 -42162

8.1 Inplace Analysis – Load Tables (Samarang)
43
Basic
Load
Case
Description
Fx Fy Fz Mx My Mz
BBA Self-Generated Weight of the Structure 0 0 -28278 -537263 537263 0
BBB Topside Payload (2500MT) 0 0 -29188 -554572 554572 0
LLA Live Load (20kPa) 0 0 -27600 -524400 524400 0
OW+X Operating Wind in +X Direction (0o) 193 0 0 0 25247 -3686
OW+Y Operating Wind in +Y Direction (90o) 0 193 0 -25516 0 3671
OW-X Operating Wind in -X Direction (180o) -193 0 0 0 -25520 3660
OW-Y Operating Wind in -Y Direction (270o) 0 -193 0 25540 0 -3671
SW+X Storm Wind in +X Direction (0o) 527 0 0 0 69535 -10004
SW+Y Storm Wind in +Y Direction (90o) 0 527 0 -69526 0 10004
SW-X Storm Wind in -X Direction (180o) -526 0 0 0 -69558 10038
SW-Y Storm Wind in -Y Direction (270o) 0 -526 0 69552 0 -9982
201 Operating Wave and Current at Samarang in 0o 266 0 0 2 12825 -5050
202 Operating Wave and Current at Samarang in 45o 185 185 -20 -9511 9511 0
203 Operating Wave and Current at Samarang in 90o 0 266 0 -12825 -2 5050
204 Operating Wave and Current at Samarang in 135o -185 185 -15 -9449 -8891 7025
205 Operating Wave and Current at Samarang in 180o -266 0 2 47 -12887 5055
206 Operating Wave and Current at Samarang in 225o -184 -184 -10 8961 -8961 0
207 Operating Wave and Current at Samarang in 270o 0 -266 2 12887 -47 -5055
208 Operating Wave and Current at Samarang in 315o 185 -185 -15 8891 9449 -7025
401 Storm Wave and Current at Samarang in 0o 1275 0 -36 -683 64811 -24233
402 Storm Wave and Current at Samarang in 45o 885 885 -48 -46145 46145 0
403 Storm Wave and Current at Samarang in 90o 0 1275 -36 -64811 683 24233
304 Storm Wave and Current at Samarang in 135o -885 885 -52 -46252 -44282 33634
405 Storm Wave and Current at Samarang in 180o -1277 0 -44 -834 -63364 24262
46 Storm Wave and Current at Samarang in 225o -875 -875 -28 44353 -44353 0
407 Storm Wave and Current at Samarang in 270o 0 -1277 -44 63364 834 -24262
408 Storm Wave and Current at Samarang in 315o 885 -885 -52 44282 46252 -33634

8.1 Inplace Analysis – Load Tables (Samarang)
44
No
Combined
Load Case
Fx Fy Fz Mx My Mz
1 2001 459 0 -74026 -1406472 1444547 -8736
2 2002 321 321 -74046 -1434025 1433835 -11
3 2003 0 459 -74026 -1444816 1406473 8721
4 2004 -321 321 -74041 -1433963 1379541 12208
5 2005 -459 0 -74024 -1406427 1368068 8715
6 2006 -321 -321 -74036 -1379457 1379471 -7
7 2007 0 -459 -74024 -1368048 1406428 -8726
8 2008 321 -321 -74041 -1379527 1433773 -12226
Operating Loads + 100-year Environmental Loads (Storm Condition)
1 4001 1802 0 -57502 -1092518 1226181 -34236
2 4002 1257 1257 -57514 -1187134 1187141 0
3 4003 0 1802 -57502 -1226172 1092518 34236
4 4004 -1257 1257 -57518 -1187241 998376 47804
5 4005 -1803 0 -57510 -1092668 958914 34300
6 4006 -1247 -1247 -57494 -998309 998305 39
7 4007 0 -1803 -57510 -958920 1092669 -34245
8 4008 1257 -1257 -57518 -998380 1187248 -47764

8.1 Inplace Analysis – Member UC (Erb West)
45
No
Member
Number
Description Member
Group
Member Section Load
Comb
Member
UC
Remarks
1 0410-0405 Deck B01 PG1500x800x30x45 1008 0.87 OK
2 0037-0039 Column C72 OD 700x25 1008 0.45 OK
3 0214-1039 Bracing GR1 OD 406.4x19.05 1002 0.25 OK

8.1 Inplace Analysis – Member UC (Samarang)
46
No
Member
Number
Description Member
Group
Member Section Load
Comb
Member
UC
Remarks
1 0410-0405 Deck B01 PG1500x800x30x45 2008 0.87 OK
2 0017-0030 Column C72 OD700x25 2006 0.47 OK
3 1039-0255 Bracing GR1 OD 406.4x19.05 2001 0.25 OK

8.1 Inplace Analysis – Deflection
47
All members are checked for
their relative deflections in
operating and storm conditions.
ERB WEST
SAMARANG

8.1 Inplace Analysis – Support Reaction
48
All members are checked for their relative deflections in operating and
storm conditions.

8.1 Inplace Analysis – Erb West (Operating)
49

8.1 Inplace Analysis – Erb West (Storm)
50

8.1 Inplace Analysis – Samarang (Operating)
51

8.1 Inplace Analysis – Samarang (Storm)
52

8.2 Accidental Analysis – Member High Stress Omitted
53
◦ Member with highest stress is located at the
inside barge deck supporting the upper
barge deck.
◦ Tested only using Erb West Data.
◦ Revised UC as below:

54
◦ Revised deflection as below:

55
◦ Revised reaction as below:

8.2 Accidental Analysis – Losing One Leg
56
◦ Tested only using Erb
West Data due to
longer utilized leg
length as compared to
Samarang.
◦ Results just to give
overall view and
pattern on the failure
◦ The underside of the
barge deck experience
high stress

57
◦ Deflection Shape:

58
◦ Support Reaction:

9.1 Inplace Analysis
60
◦ From the inplace analysis run from the two studied field, Erb West
and Samarang. The member stresses are not showing any
significant difference
◦ It is expected that if the soil parameters is included, better
comparison on the inservice analysis can be made.
◦ Since the gravity loads are applied at the centre symmetrically, it is
more obvious to identify the critical leg with regards to the direction
of the environmental loadings.
◦ During head or beam sea wave directions (0o, 90o, 180o and 270o),
the farthest outer column experienced highest reaction. While during
diagonal wave direction (45o, 135o, 225o and 315o), the farthest corner
leg experienced highest reaction. These explained in figures below.

9.1 Inplace Analysis
62
◦ In overall, support reactions are higher at Samarang field as
compared to Erb West though the water depth is lesser than Erb
West. The 1-year and 100-year wave period, (Tass) values for
Samarang are higher compared to Erb West. It is concluded that the
wave period causes a significant shear force impact to the structure.

63
◦ After removing the member with highest stress (UC=0.87),
surprisingly the highest member unity check reduced from 0.87 to
0.81.
◦ The deflection also improved from maximum of deflection UC of 0.93
to 0.92.
◦ The reaction still shows the same distribution pattern as in inplace
analysis.
◦ The overall outcome may happen when there are redundant
function and stress distribution among the members. Therefore, the
member can be omitted in further optimization exercise.

64
◦ Highest member stress
experienced by underside of
the barge deck.
◦ The three other legs experience
very high stress
◦ Possibility of collapse or
deformation need to be further
examined using elastic plastic
analytical software.
◦ In all wave direction, Leg 3,
specifically the inward corner
(Joint 0013) experienced the
highest reactions.

CONCLUSIONS &
RECOMMENDATIONS
10
65

Conclusions
66
◦ This new concept of relocatable offshore platform can be considered
as an option to be further studied and optimized.
◦ The inplace analysis shows acceptable.
◦ Losing 1 leg can cause catastrophic damage to the structure,
environment, and personnel on duty. Therefore, any possible events
that may cause platform instability need to extremely scrutinized
and studied to avoid such incident.
◦ Further study may require soil information for dynamic analysis and
soil-structure interaction for better outcomes.
◦ It is also recommended that the jacking system connecting the hull
and the column can be designed as pinned-type connection.

70
https://2hoffshore.com/wp-
content/uploads/2016/02/2012-OSEA-Modular-Design-
for-Low-Cost-Minimum-Facilities-Platforms.pdf pg15

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