An Offshore supply vessel is a multi-task vessel and has to be designed for many different purposes. This is contrary to most other ships used worldwide. In general, the geographical location where the offshore activity takes place is an important indicator of the choice of supply vessel. Factors like weather conditions, the amount of equipment needed and the distance from the shore are important for what properties the vessel should have. The deep-water oilfield market is becoming more important as the conventional oilfield market in shallow water cannot meet the energy requirements from the consuming market. The Offshore Supply Vessels (hereafter it is called OSVs) market is becoming booming and the demand for OSVs has never reached the extent like today in previous periods. In this project, an offshore supply vessel will be designed according to ABS Rules.

1. Offshore Support Vessels Design
By:
Ahmed Taha Abd El-Mawla

2. Contents
• Design Of Vessel
• Intact Stability
• Construction Of Vessel
• Structural Design : Hull Girder ,Secondary ,Tertiary
• Resistance Of The Vessel
• Power And Machinery Selection
• Design Procedure Of Propeller
• Propeller Cavitation
• Ship Motions and Seakeeping

3. Design and operating capabilities
• Large and open aft deck.
• Highly maneuverable, particularly at low speed.
• Storage for offshore exploration and production activities:
such as bulk mud and cement, potable water
• Wheel house all - round visibility (have forward & aft control)
• High engine power for towing operations.
• Some OSVs are equipped with big fire pump with monitors for external
firefighting system.
• Dynamic Positioning (DP) system is very important for all types of OSVs.

4. Features of offshore supply vessel
Work deck
Anchor roller
Steering gear
Ducted propeller
Stern TubeTransverse Thruster
Tanks For dry bulk
Deck cranes
Propeller shaftGear box
Maine engine
Life raft
MOB-boat with crane
Storage reel for steel
wires for anchor
BridgeFirefighting monitor
Switchboard

5. Design of vessel
• The design of a ship is an iterative process, in which early estimates
are made.
• Then repeatedly corrected.
• Design and Construction – IMO A.469 (XII)
• Design spiral• Main Particulars
Length overall = 20 m
Length B.P. = 19.3 m
Breath moulded = 6.66 m
Depth moulded = 3.3 m
Design draught = 2 m

6. Design of vessel
• Lines Plans
Before After

7. • Generation of the hull surface
Design of vessel

8. • General Arrangements
Design of vessel
Outboard Profile

10. • Preliminary hydrostatic calculations
Displacement 122.9 t
Volume (displaced) 119.895 m^3
Draft Amidships 2 m
Immersed depth 2.015 m
WL Length 19.392 m
Beam max extents on WL 6.144 m
Wetted Area 136.187 m^2
Max sect. area 7.821 m^2
Waterpl. Area 105.717 m^2
Prismatic coeff. (Cp) 0.79
Block coeff. (Cb) 0.499
Max Sect. area coeff. (Cm) 0.636
Waterpl. area coeff. (Cwp) 0.887
LCB length -0.158 m
LCF length -0.504 m
LCB % -0.813
LCF % -2.599
KB 1.333 m
BMt 2.41 m
BML 23.723 m
GMt corrected 3.743 m
GML 25.056 m
KMt 3.743 m
KML 25.056 m
Immersion (TPc) 1.084 tonne/cm
MTc 1.588 tonne.m
Design of vessel

11. Intact Stability
• Loading Conditions
1. Light weight Condition
2. Full load Condition
3. Vessel with 10% of consumables ,departure condition.
4. Vessel with 10% of consumables ,arrival condition.

12. Equilibrium
Draft Amidships m 1.960
Displacement t 118.3
Heel deg 0.0
Draft at FP m 2.012
Draft at AP m 1.909
Draft at LCF m 1.958
Trim (+ve by stern) m -0.103
WL Length m 19.399
Beam max 6.123
LCB. (+ve fwd) m -0.018
LCF. (+ve fwd) m -0.479
Full load Condition
KB m 1.309
KG fluid m 1.749
BMt m 2.447
BML m 24.444
GMt corrected m 2.006
GML m 24.003
KMt m 3.755
KML m 25.752
Immersion (TPc) tonne/cm 1.075
MTc tonne.m 1.464
Max deck inclination deg 0.3033
Trim angle (+ve by stern) deg -0.3033
𝑮𝑴 = 𝑲𝑴 − 𝑲𝑮 = 3.755-1.749 = 2.006

13. Large Angle Stability
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 10 20 30 40 50 60 70 80 90 100 110 120
GZm
Heel θ deg.
Full Load GZ - θ Curve
GZ
Initial GM
Max GZ
Range of Stability
θ 𝒇
Initial GM
Max GZ
θ

14. CRITERIA REQUIRED
Area between 0 and angle
of maximum GZ
3.1513 𝒎. 𝒅𝒆𝒈
Area from 30 to 40 deg. 1.7189 𝒎. 𝒅𝒆𝒈
Maximum GZ 0.200 𝒎
Angle of maximum GZ ≥15 𝒅𝒆𝒈
Initial GMt 0.150 𝒎
full load
Condition
23.7920
𝒎. 𝒅𝒆𝒈
9.9358 𝒎. 𝒅𝒆𝒈
1.005 𝒎
38.2 𝒅𝒆𝒈
2.006 𝒎
IMO A.749 (18) Ch4,5 Offshore supply vessels

15. Construction of vessel
• Calculation in detail according to the ABS rules:
Offshore Support Vessels 2016-Part 3 Hull Construction and Equipment
• CHAPTER 2: Hull Structures and Arrangements

16. Midship Section
6.667 m
0.5 m 1.65 m
Long.
L.75*50*6
C.G.
T.150*130*123.3 m
Deck 7.5mm PL.
Side 7.5mm PL.
Bottom 8mm PL.

17. 3D Model Representation

18. Structural Design Loads
• Direction of the working load
• Frequency of occurrence
• Distribution pattern on the hull structure
• Behavior in the time domain
the best way to categorize loads on the hull structure is as follows:
• Longitudinal strength loads
• Transverse strength loads
• Local strength loads

19. Strength Evaluation
• If structural damage to a ship occurs, it means that the load acting on
the structure must have exceeded the maximum limit of structural
strength

20. Procedure of Structural Strength Evaluation
• Determine an initial system of
structural members
• Presume a magnitude ,
direction and probability of
load
• Assume failure mode of
structure due to load
• Select an appropriate analysis
method
• Choice of an acceptable
strength criteria for particular
failure mode
• Evaluation of the response for
given criteria

21. Modes of structural failure
the following modes are significant for structural designers:
• Yielding
assume that a tensile load is gradually applied to a structure, then
some elongation might be induced and be proportional to the load
increment as long as the load is small. Once the load exceeds a certain
critical value, then elongation would increase rapidly.
• Buckling
• Fatigue

22. Hull Girder Loading
• Ship hull girder loads consist of static and dynamic components.
• The still-water component results from the difference between the
distributions of the various weight items and the distribution of the
supporting buoyancy forces along the ship length.
• The design load is the maximum load likely to occur over a specified
period of time.

24. The Nature of Hull Girder Loads
A ship floating at rest in still-water is subject to gravitational forces and
hydrostatic pressures over the immersed volume of the hull.
Hull girder loads could be categorized as follows:
• Hull girder bending moment
• Hull girder shear loading
• Hull girder torsion loading
• Local loadings

25. Stillwater Shear Force and Bending Moment
• The longitudinal strength of a ship, the ship hull girder may be treated
as a non-uniform beam.
Wave-Induced Components
• The wave induced shear force and bending moment components
result from the distribution of the forces of support throughout the
length of a ship during her passage among waves.
Dynamic bending moment (whipping, slamming)
The Nature of Hull Girder Loads

26. Secondary Loading and Stresses
For longitudinally stiffened bottom structures, the strength members
sustaining secondary stresses are bottom girders, bottom and tank top
longitudinal and plating

27. Secondary Loading in Bottom Assemblies

28. Creating and Analyzing a Model in ANSYS :
• Creating a Project Schematic, here Analysis
Systems is Static Structural
• add or modify material data at Engineering
Data
• Creating a Geometry
• Applying a boundary condition and a load to
the model
• Meshing the model
• Creating a solution module
• Start the analysis
• Viewing the results of analysis

29. Bottom Total Deformation

30. Bottom Equivalent Stress

31. Bottom Total Bending Moment

32. Bottom Axial Force

33. Total Shear Force

34. Torsional Moment

37. Side Total Deformation

38. Side Equivalent Stress

39. Side Total Bending Moment

40. Side Axial Force

41. Side Total Shear Force

43. Tertiary Loading and Stresses
1. Tertiary Loading Stresses on Bottom Plating
2. Tertiary Loading Stresses on Bottom Longitudinal
3. Tertiary Loading Stresses on Bottom transverse
4. Tertiary Loading Stresses on Tank Top Longitudinal
5. Tertiary Loading Stresses on Side Longitudinal
6. Tertiary Loading and Stresses on Deck Longitudinal

44. Tertiary Loading on Bottom Plating
Creating and Analyzing a Model in ABAQUS/CAE:
• Creating a Model Database
• Creating Models
• Creating Parts
• Creating materials
• Defining and assigning section properties
• Assembling the model
• Defining analysis steps
• Applying a boundary condition and loads
• Meshing the model
• Creating and submitting an analysis job
• Viewing the results of analysis

45. Tertiary Loading on Bottom Plating

46. Tertiary Loading on Bottom Longitudinal

47. Tertiary Loading on transverse

48. Tertiary Loading on Tank Top Longitudinal

49. Tertiary Loading on Side Longitudinal

50. Tertiary Loading on Deck Longitudinal

51. Tertiary Loading and Stress Summary

52. Resistance of the vessel
0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
0 2 4 6 8 10 12 14 16 18 20 22
ResistanceKN
Speed Knot
Resistance
Holtrop Res
Compton Res110.7 KN

53. 𝑸𝑷𝑪 = 𝟔𝟒 %
𝜼𝒕 = 𝟗𝟓 %
𝑩𝑯𝑷 = 𝟔𝟓 %
Power And Machinery Selection
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
0 2 4 6 8 10 12 14 16 18 20 22
PowerKW
Speed KN
Power
Holtrop Pow
Compton Pow
797 KW

54. Estimate total calm water
Resistance Rt at Speed Vs
Effective power PE = Rt * Vs
Estimate quasi-propulsive coefficient
Estimate Wake and Thrust Deduction
Estimate
ηH = hull efficiency
ηR = relative rotative efficiency
ηs = Shaft efficiency
Brake power
η 𝒉𝒖𝒍𝒍
P 𝑬 P 𝑻 P 𝑫 P 𝒔𝒉𝒂𝒇𝒕 P 𝑮 P 𝒃
η 𝑮.𝑩η 𝑺𝒉𝒇𝒕η 𝒐
P 𝒐
η 𝑹𝑹
η 𝑩
η 𝑫= QPC
η 𝑻
Delivered power , Shaft power
ηG = Reduction Gear

55. Manual Using MAXSURF

56. Machinery selection C18 ACERT TIER 3

57. Calculate the effective power 𝑃𝐸
Assume quasi-propulsive coefficient
Calculate the delivered power 𝑃𝐷
Using 𝑩 𝑷 - 𝛿 charts
Calculate the propeller diameter 𝑫 𝒐
higher open water efficiency 𝜂
𝑃𝑂 from all 𝑩 𝑷 - 𝛿 charts
Calculate the speed of advance 𝑉𝑎 of
the propeller VA = VS ( 1 - w )
Calculate the ship hull
efficiency, 𝜂𝐻𝐿
Re-calculate quasi-propulsive
coefficient,
QPC= 𝜂𝑃𝑂 ∙ 𝜂𝑅𝑅 ∙ 𝜂𝐻𝐿
BP =
PD
0.5 n
VA
, Z = 4
𝑫 𝒐 =
δopt VA
n
Compare the calculated QPC with that
initially assumed value, then iterated
several times , starting with the resultant
QPC
Design Procedures of propeller
0.64
398.65 KW
622.89 KW
12.686 Knot
26.123
3.8059 ft
60 %
𝜹 = 𝟏𝟖𝟎
𝜂𝑃𝑂 = 60%

60. The cavitation forms
Detrimental effects of cavitation,
• Effects on propeller performance
• Cavitation damage of propellers
• Cavitation-induced vibrations and noise.

61. Prediction of Propeller Cavitation by Keller Method

62. Overall seakeeping performance
• The sea states
ranges of wave height, period
and direction
• The ship responses
ship speed and the ship’s heading
• Limiting conditions

63. Wave Spectra Representation
• Irregular ocean waves are typically described in terms of a wave
spectrum. This describes a wave energy distribution as a function of
wave frequency.

65. Characterizing Vessel Response
The Response Amplitude Operator (RAO) :
• describes how the response of the vessel varies with frequency.
• It may be seen that the RAOs tend to unity at low frequency, this is
where the vessel simply moves up and down with the wave
• At high frequency, the response tends to zero since the effect of many
very short waves cancel out over the length of the vessel
• An RAO value of greater than unity indicates that the vessel's
response is greater than the wave amplitude (or slope).

68. Motion Sickness Incidence (MSI)

70. Root Mean Square (RMS)
m0 : The mean square, of the spectrum is :
the area under the spectrum and gives a measure of the total
response of the vessel.
The RMS is the square root of the mean square
SA = Significant Amplitude is twice the RMS value
m0 RMS SA

71. -40
-30
-20
-10
0
10
20
30
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
roll[deg]
time[s]
Roll Decay
Roll Decay

75. Thank You