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A. Papanikolaou, NTUA-SDL 1
Review of regulatory framework of Damage Stability of Dry Cargo and Passenger Ships
Two main categories of regulatory concepts and methodologies for the assessment of ship’s damage stability are nowadays in use, namely the deterministic and the probabilistic ones, leading to corresponding regulatory survivability standards (criteria). • Deterministic approaches to ship’s damage stability are based on prescriptive, semi-empirical rules and criteria derived from statistical analysis of historical damage data and practical experience. Because of the semi-empirical way of deriving the applied criteria, these methods cannot ensure a reliable minimum level of required survivability in case of new ship designs deviating from the past, nor is the attained level of ship safety known. • The probabilistic approach to damage stability relies on a rational statistical assessment of historical accidental data and combines this statistical information with semi-empirical criteria to more rationally assess
ship’s survivability by use of a probabilistic concept that takes into account a vast amount of possible damage scenarios with proper weight.
US, Nov 2015
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A. Papanikolaou, NTUA-SDL 2
Assessment methods of damaged stability of ships
•Deterministic Approach • Semi-empirical, prescriptive requirements, e.g. SOLAS74, SOLAS 90 • Performance-based (experimental or numerical simulation approaches), e.g. SOLAS 95 – Stockholm Agreement
• Probabilistic Approach • A.265, equivalent to SOLAS74 • Risk-based, …SOLAS 2009 • Goal-based, …new SOLAS 2016+…
US, Nov 2015
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A. Papanikolaou, NTUA-SDL 3
Deterministic vs. Probabilistic Approach to Ship Stability
The probabilistic assessment allows the determination of ship’s specific survivability (safety) level against capsize in case of flooding due to collision damages through her Attained Subdivision Index (probability of survival collision damages), whereas a deterministic damage stability standard does not correspond to a quantifiable safety level.
US, Nov 2015
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A. Papanikolaou, NTUA-SDL 4
Recent revisions of SOLAS damage stability regulations
(last 40 years) The regulatory requirements on ship’s damage stability differ depeding on ship type: - Passenger ships (SOLAS) - Dry cargo ships (SOLAS) - Liquid cargo ships (MARPOL) Main recent revisions of damage stability regulations for passenger and dry cargo ships.
1974
SOLAS
1974
1990
SOLAS 74
rev. 1990 SOLAS 74
rev. 1992 SOLAS 74 Rev. 1995
199 2 199 5
SOLAS
Part B - 1
Passenger Ships
Dry cargo ships
2009
SOLAS 74 Rev. 2009
SOLAS 74
Rev. 2009
US, Nov 2015
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A. Papanikolaou, NTUA-SDL 5
Passenger ships (deterministic SOLAS 90 requirements)
Main damage stability criteria of SOLAS 90 for passenger ships Examine for the maximum loading draft Intermediate Stages
GZ 0.05m, Range > 7o
θe < 15o
GZ
θ
GM 0.05m
A rea 0.015 m rad
Final Stage
Range 15 degrees
A ngle of inclination
7o 1CFL
12o 2CFL
GZmax GZreq
θrange = min (22o 1C FL, 27o 2CFL, θFLOODING, θ(GZ=0))
Intermediate Stages
GZ 0.05m, Range > 7o
θe < 15o
GZ
θ
GM 0.05m
A rea 0.015 m rad
Final Stage
Range 15 degrees
A ngle of inclination
7o 1CFL
12o 2CFL
GZmax GZreq
θrange = min (22o 1C FL, 27o 2CFL, θFLOODING, θ(GZ=0))
04.0
entHeelingMom
GZreq
Heeling moment: - Due to crowding - Launching of crafts of one side - Due to wind pressure
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A. Papanikolaou, NTUA-SDL 6
RoPax – Ro-Ro passenger ships (deterministic-performance based)
Water On Deck
Stockholm Agreement-Resolution 14: for NW Europe (after the Estonia Accident)
EU Directive 2003/25/EC: for South Europe (after the SAMINA accident)
- In addition to the previously mentioned SOLAS 90 criteria, RoPax ships need to
fulfill the same criteria, assuming certain amount of WOD (Water On Deck,
namely their car deck)
-This hypothetical flood water mass is function of
- Damage freeboard
- Significant wave height in the area of operation
- Max flood water mass:
- 0.5m for 4.0m sign. wave height and 0.5m damage freeboard
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A. Papanikolaou, NTUA-SDL 7
RoPax – Ro-Ro passenger ships (deterministic-performance based)
Water On Deck
-Calculatory method: formal compliance with the specified regulation
Alternatively (equivalent model test method, Res. 14),
- Model tests with model of damaged ship in side waves: equivalent
model test method, performance-based
-Generally: it proves in practice that the formal calculatory method is
by far more onerous (very conservative) with respect to ship’s survival
conditions. Thus, the equivalent model test method is mostly preferred
US, Nov 2015
Pres-4m-out.wmv
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A. Papanikolaou, NTUA-SDL 8
Deterministic or Probabilistic Approach?! Harmonization of existing & new damage stability
regulations
The harmonization of existing damage stability rules was decided by IMO and led to a unified assessment framework based on the probabilistic concept of estimating the damage stability of dry cargo and passenger ships.
The main goal of harmonization referred to the definition of survivability levels for dry cargo and passenger ships that are equivalent to those defined by the at that time in-force regulations for new-buildings.
The outcome of the harmonization process was SOLAS 2009!
Status at that time (years 2000-2003, project HARDER)
REFERENCE: MSC1/Circ. 1226 (2007): Interim explanatory notes to the SOLAS Chapter II-1 Subdivision and damage Stability Regulations
Basic ship type In force regulation Model
Dry cargo ships SOLAS B-1 Probabilistic
Passenger ships Resolution A.265 Probabilistic
Passenger ships SOLAS 90
(SOLAS 95)
Deterministic
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A. Papanikolaou, NTUA-SDL 9
SOLAS 2009 – Damage stability
Calculation of the attained subdivision index Α
Pi-factor: Probability that only the compartment or group of compartments under consideration may be flooded. • Maximum damage length changed to 60 m in SOLAS 2009 (noting that it was 3%L + 3m, but not more than 11m in SOLAS 90!). • Damages of up to B/2 should be assumed (allowing penetration of longitudinal centre line bulkheads) REFERENCE: MSC1/Circ. 1226 (2007): Interim explanatory notes to the SOLAS Chapter II-1 Subdivision and damage Stability Regulations
tj
j
jjji svPA1
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A. Papanikolaou, NTUA-SDL 10
Details of Probabilistic Model
Basic Approach
Probability that the ship will encounter
damage, P1
Probability of the resulting damage
location and extent, P2
Probability of the ship surviving the
damage, P3
Probabilistic Analysis of damage survivability
Probability that the ship will encounter
damage, P1
Probability of the resulting damage
location and extent, P2
Probability of the ship surviving the
damage, P3
Probabilistic Analysis of damage survivability
Probability that the ship will encounter
damage, P1
Probability of the resulting damage
location and extent, P2
Probability of the ship surviving the
damage, P3
Probabilistic Analysis of damage survivability
Probability that the ship will encounter
damage, P1
Probability of the resulting damage
location and extent, P2
Probability of the ship surviving the
damage, P3
Probabilistic Analysis of damage survivability
Collision/ Contact Grounding Ramming Fire/Explosion Other
Accidents
A, R
Indices
Deterministic Elements
in Probabilistic Rules
Collision/ Contact Grounding Ramming Fire/Explosion Other
Accidents
A, R
Indices
Deterministic Elements
in Probabilistic Rules Examination of probable damage scenarios
Loss of Watertight Integrity
A (710) vs. B (199) - 1.2 Damage length
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
l/Lpp
f(x)
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
F(x
)
PDF-A
PDF-B
CDF-A
CDF-B
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A. Papanikolaou, NTUA-SDL
Risk Model (Event Tree) for collisions of cruise ships
11
Slow sinking: 72% Fatalities: 5%
Fast sinking: 18% Fatalities: 80%
27.0%
42.3077% Sinking (A-Index)
73.0%
Water ingress
4.0%
57.6923% 0.006%
37.5% Operational State
27.0%
42.3077% Sinking (A-Index)
73.0%
Water ingress
23.0%
57.6923% 0.0348%
27.0%
11.7647% Sinking (A-Index)
73.0%
Water ingress
73.0%
88.2353% 0.1688%
0.699% Initiator
62.5% 0.4369%
Collision
99.301% 99.301%
Ship type
No
Yes
Struck
En Route
Yes
No
No
Limited Waters
Yes
No
No
Terminal
Yes
No
No
Striking
Yes
Yes
Yes
US, Nov 2015
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A. Papanikolaou, NTUA-SDL 12
Probabilistic Model
The probability of survival of a ship after a damage (LOWI) due to collision with another ship of comparable size is expressed by the Attained Subdivision Index A. When calculating this index, a series of different damage scenarios for pre-determined loading conditions (full and partial load) are taken into account. The general form of the index A is the following:
wfi: weight functions for the various loading conditions (full, partial, light) Αi : attained subdivision index for each examined loading draft The attained subdivision index should not be less that the required index R, which is specified in the SOLAS regulations.
ii AwfA
Required Index R 1. Cargo ships, function of L 2. Passenger ships, function of L,
number of POB N and N1 (lifeboat capacity)
Summation of attained indices for various loading conditions: A = 0.4As + 0.4Ap + 0.2Al
32
11CNCL
CR
S
Dry Cargo Ships (L>100m): C1=128, C2=0, C3=152. Passenger Ships: C1=5000, C2=2.5, C3=15225.
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A. Papanikolaou, NTUA-SDL 13
Modelling of survivability levels
The general formulation of new required survivability levels (project HARDER)
It should be noted, that due to the large scatter of the sample data of passenger ships, part of which were exhibiting unacceptably low attained indices, two alternative formulations for the R index were originally proposed by SLF47 for adoption by MSC 80. Alternative 1 corresponds to the best regression fitting of a reduced sample of ships with satisfactory levels of survivability, whereas Alternative 2 (finally adopted) considers an enhanced sample of passenger ships at worse regression fitting.
32
11CNCL
CR
S
Required Subdivision Index
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 1000 2000 3000 4000 5000 6000
L + N
A,
R
A-f_heel_int
SLF47 Proposal,
Alt 2
C1=5000,
C2=2.5
C3=15225
SLF47 Proposal,
Alt 1
C1=2500, C2=3.5
C3=5413
Following a series of deliberations at IMO-SLF-MSC, IMO-MSC80 (2005), the finally adopted the following numerals for the Ci coefficients
Dry Cargo Ships (L>100m): C1=128, C2=0, C3=152. Passenger Ships: C1=5000, C2=2.5, C3=15225.
US, Nov 2015
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A. Papanikolaou, NTUA-SDL
Comparison of Required Subdivision Indices
25
200005
230012
pobRIndex
000,6for97.0
000,1for9.0
1
pob
pob
RIndex
Pending final discussions/approval
by IMO
US, Nov 2015
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