Damage Stability
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Transcript of Damage Stability
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An insight into various Damage Stability Standards
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Scope• Damage Stability an Introduction
• Evolution of Damage stability rules
• Comparison of damage lengths
• Comparison of other damage criteria
• Probabilistic analysis of damage Stability
• Damages Post WW II – Change of threat
• Latest developments
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Introduction• Terms associated with Damage stability –
– Susceptibility• Signature management• Countermeasure
– Vulnerability• Impairment after damage• Ability to recover
– Survivability• Positioning of bulkheads• Location of damage control deck• Openings in WT bulkheads• System Designs
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History of Damage stability rules• 1947- Study by BuShips
– 24 ships with torpedo hits during World War II analysed– Length Criteria developed ( 15 % LBP)
• Adoption of Wind Criteria from Sarchin and Goldberg, 1962– Pacific Typhoon 1944 , US lost 790 men and 3
destroyers .
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Comparison of Damage Stability Criteria –
Deterministic Approach
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Basic considerations for stability after damage
• Length of damage.
• Residual Reserve of buoyancy (only Considered till WT bulkhead deck)
• Angle of list
• Ability to resist wind and roll
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After effects of Damage
• Parallel sinkage.
• List
• Trim
• Reduced ability to resist wind and roll
30% loss of ROB
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Length of damage criteria
• 12.5% for other ships
Hospital ships/ Troop carriers
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• UK/US – Bkhd to be WT upto deck above apex of V – line
• Japan – No Bkhd penetration below damage control deck
• Canada – No WT door/hatch below damage waterline on main WT bulkheads.
• Germany - Doors below Bulkhead deck may be given along ships center line
Provision of Openings
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V Line – US Navy
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V Line – UK Navy
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Merchant Navy
• WT sliding doors – allowed below damage waterline– Electrically/ hydraulically operated– Remote operability
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List/Loll after DamageCountry UK US JAPAN ITAL
YCANADA FRANCE GERMANY
Angle of List/ Loll
< 200 < 150 - < 150 < 150 < 200
<150 after cross flooding
< 250
Cargo Vessel
Passenger Vessel
25 0 - 300 7 0 - 150
SOLAS
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Roll back angleCountry UK US JAPAN ITALY CANADA FRANCE GERMANY
Angle of List/ Loll
150 100
for a 5000 t ship
Calculates as per Sea State
- < 150
for a 5000 t ship
150 -
RUSSIA
Roll amplitude = kX1X 2Y
K – Appendage factorX1 – B/TX 2 - C B
Y – sqrt(GM)/B
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Post Damage - Roll curve US Navy
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Origin – Roll back angle
• Not clearly specified in any literature.
• 250 roll observed during WW II – intact ships
• Ships roll depends on –– Sea State– GM of the Ship– Geometry of the Hull
Japan & Russia – Considers Sea State for calculation of roll
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Other Criteria
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Damage stability philosophies
• Canada – – Heel after flooding kept min. expending least Reserve
buoyancy (Cross flooding)
• Germany – – Probability analysis for assessment of damage effects , if
Ship design not satisfying their criteria
• Italy - – Survivability - primary concern choosing dimensions, hull
form, subdivision and systems– Ability to continue mission. (Systems design)
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• United Kingdom – – Placement of transverse bulkheads, adequate reserves
of buoyancy and stability – Preserve mobility and operational functions.
• Australia - – Adopted from US navy – changed loading cond.
Damage stability philosophies
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Probabilistic Damage Stability – SOLAS (MSC 281(85))
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Calculation Method
• Damage is assumed to have occurred • Probability of damage location and extent p • Probability that the vessel can survive s• Probability of vessel surviving this damage p . s • Attained Subdivision Index (A)
– Total probability of survival as sum of all probabilities A = Σ (pi . si)
• R is the required subdivision index – Formula based on length, No. of passengers R
• Requirement is that A > R A > R • Probabilities are based on actual statistics of casualties
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Inputs for Pi• 3 loading cases considered.
– Deep– Partial– Light
• Max. adjacent zones to damage• Longitudinal zone location & Subdivision• Transverse subdivision
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Inputs for Si• Equilibrium heel angle
• Down flooding angle
• GZmax before down flooding.
• Range – From equilibrium angle to downflooding angle
• Flooding stage – Before reaching equilibrium
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Damages Post World War II – changes in threat
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Post world War II
• Underwater mines , Korean war – 4 minesweepers lost, larger ships survived damage
but left nonoperational
• Above water combat damage – Exocet missiles , Aerial Bombs– Ships sunk by firefighting water
• Collision - Routine operation
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Summary - Major damages post WW II
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Warship Damage Stability – Latest developments
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Latest Trends in ship design• Increased payload to displacement ratio
• Enhanced Weapon and sensor capability, Reduced RCS
• Reduction in structural weight
• Design for Enhanced Survivability
• Capability to continue mission
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Probabilistic approach• Susceptibility ( PH ) – Inability to intercept and
being detected (Signature management/ Countermeasures)
• Vulnerability ( PV ) - Impairment during a damage
• Killability, PK = PH x PV
• Probability of Survival = 1 - PK
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Probabilistic approach
• Point of hit– Depends on Weapon
• Exocet hits at Waterline level• Harpoon hits at Superstructure level.• Heat seeking missiles on funnel and engine
area
• Length of damage – Warhead used.
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Survivability Index for naval Ships
One of the proposed model of survivability index
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Conclusion
• Ship design for – Vulnerability & Survivability
• Optimal watertight compartmentation• Variety of damage scenarios and
operational/environmental conditions.• Location of Damage control deck
– Restrictions • Space requirements for accommodation,
weapon, vital systems• Minimization of structural weight
Very difficult without an
optimisation algorithm.
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Way Ahead
• Database of previous damages – effects/causes
• Understand and define our priority-– Survivability ( Bhkd positioning, form)– Fight Hurt ( System design)
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THANK YOU
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Type 21 Frigate- HMS Ardent - hit by 1,000 lb aerialbombs- Sank
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Type 42 Air Defence Destroyer - HMS Sheffield - AM39 Exocet. - Warhead failed to explode but Caused Uncontrollable Fire/Sunk
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• Ships designed for critical damage of 15 % LBP survived
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Extent of damage• Longitudinal-
- 15% LBP along the length • Transverse-
- Only one side of the double bottom tank
• Vertical-- Till the bulkhead deck
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15% LBP Damage Simulation
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15% LBP Damage Simulation
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Wind Criteria
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Dynamic Stability Simulation
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Costa Concordia- Italian Cruise ship sinking
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NAPA Simulation-Costa Serena
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NAPA Simulation-Costa Serena
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NAPA Simulation-Costa Serena