probabilistic damage stability rules for cargo ships and sps (part b – solas 2009) paris, march...

Probabilistic Damage Stability Rules for cargo shipsand SPS (Part B – SOLAS 2009)

Paris, March 2011

Marine Technical DepartmentStability Section (DT5)

2SOLAS 2009– New Probabilistic Damage Stability Rules – Copyright Bureau Veritas, March 2011

Probabilistic concept

Stability criteria to be satisfied

Parameters to be considered

Concepts for simplified analysis

Openings, controls & escape routes

Bottom damage

Minimum required GM

SOLAS 92 and SOLAS 2009

CONTENTS

APPLICATION

SOLAS PART B – 1

MSC.281(85) : Explanatory notes to SOLAS CH II-1

Dry cargo ships with type B freeboard

L > 80 m, if constructed on or after 1 January 2009

L is the length as defined in the ICLL in force

For SPS : MSC.266(84) : application depending on

flag requirements.

PROBABILISTIC CONCEPT

What is the basis of the probabilistic concept?

The probabilistic concept is based on the probability of survival after collision (damaged ship condition)

This probability of survival is expressed by the attained index A

The attained index A is obtained from the summation of the partial indices As, Ap, Al

For which values of attained index A do we consider a ship as surviving?

The requirement for the survivability of the ship is set by the required index R

Therefore, the attained index A is to be compared with the required index R

STABILITY CRITERIA TO BE SATISFIED

Four criteria need to satisfied for cargo ships/SPS

1. As ≥ 0.5R/0.9R, and

2. Ap ≥ 0.5R/0.9R, and

3. Al ≥ 0.5R/0.9R, and

4. A ≥ R

Partial attained index

As : corresponds to the deepest subdivision draught ds

Ap :corresponds to the partial subdivision draught dp

Al : corresponds to the lightest subdivision draught dl

REQUIRED INDEX R FOR CARGO SHIPS

Where:

Ro = R as calculated for Ls > 100 m

10080,

100,152

REQUIRED INDEX R FOR PASSENGER SHIPS/SPS

225,155.2

000,51

N= N1+ 2 N2 with

N1, number of persons for whom lifeboats are provided and

N2, number of persons the ship is permitted to carry in excess of N1

N can be reduced to a minimum of N1+N2 subject to the agreement of the flag

Each partial attained index is a summation of the contribution from all damage cases taken into consideration, using the following formula:

Where:

i : damaged zone or group of compartments under consideration

c : the considered loading condition

lps A2.0A4.0A4.0A

ATTAINED INDEX A

1iiiiic ]sv)[r(pA

Example:

p(j=3) : represents the probability that only zone number 3 will be flooded taking into account the transverse subdivision (factors r1, r2, r3)

FACTORS OF PROBABILITY

Example 1: Calculation of damage cases

Vertical limit: v1

Penetration: r1

Case Nr Damaged spaces

Transverse extent (r)

Vertical extent (v) s-factor

1 3 r1 v1 s3

2 3+2 r1 v1 s32

3 3+2+1 r1 v1 s321

Select the case whichgives the smallest value for s: MIN {s3;s32;s321}

Vertical limit: v2 = 1Penetration: r1

4 3+4 r1 1 - v1 s34

5 3+4+2 r1 1 - v1 s342

6 3+4+2+1 r1 1 - v1 s3421

Select the case whichgives the smallest value for s: MIN{s34;s342;s3421}

Vertical limit: v1

Penetration: r2

4 3+6 1 - r1 v1 s36

5 3+6+2+5 1 - r1 v1 s3625

6a 3+6+2+5+1 1 - r1 v1 s36251

6b 3+6+2+5+1+8 1 - r1 v1 s362518

Select the case whichgives the smallest value for s: MIN{s36;s3625;s36251/s362518}

Case 6a or 6b depending onB/2 exceeding the CL or not

PARAMETERS TO BE CONSIDERED

Watertight bulkheads and decks

Weathertight bulkheads and decks

Doors (watertight, weathertight of sufficient tightness and strength to restrict the flow

Air pipes

Ventilators

Piping systems

Horizontal evacuation routes

Vertical escape hatches

Controls: operation of watertight doors, equalisation arrangements, valves on piping or ventilation ducts, etc.)

Permeability of spaces

PARAMETERS TO BE CONSIDERED

Other figures for permeability may be used if substantiated by calculation

Spaces Permeability

at draught ds

Permeability

at draught dp

Permeability

at draught dl

Appropriated to stores 0.60 0.60 0.60

Occupied by accommodation 0.95 0.95 0.95

Occupied by machinery 0.85 0.85 0.85

Void spaces 0.95 0.95 0.95

Intended for liquids 0 or 0.95 * 0 or 0.95 * 0 or 0.95 *

Dry cargo spaces 0.70 0.80 0.95

Container spaces 0.70 0.80 0.95

Ro-ro spaces 0.90 0.90 0.95

Cargo liquids 0.70 0.80 0.95

* whichever results in the more severe

Specific requirements for SPS

CONCEPTS FOR SIMPLIFYING THE ANALYSIS

V-lines concept

Important factors for the calculation of the s-value:

θe : Equilibrium heel angle

θv : Angle where GZ < 0 or submersion of unprotected openings (downflooding point: openings cannot be closed weathertight)

V-lines concept

The envelope curve of worst waterlines after damage for all the damage cases giving positive contribution to the attained index A

Type of V-lines

“Watertight V-lines” derived from equilibrium heel angle (final or intermediate stages of flooding)

“Weathertight V-lines” derived from positive range (of GZ-curve)

Input for the calculation of the V-lines

Bulkheads limiting the boundary of damage under consideration

Decks limiting the boundary of damage under consideration

V-lines concept

V-lines from positive range

V-lines from equilibrium

Construction

Scantling calculation (sufficient strength to resist flooding loads)

Machinery

Position of ventilators, air pipes

Electricity

Control of watertight doors, valves, etc.

Safety

Horizontal evacuation routes

Vertical escape hatch

Escape routes, etc.

Stability

Verification of progressive flooding

No immersion of openings

Watertight openings

Weathertight

openings

Safe Area concept

Area far away from side shell (damage)

Probability (r-factor) to have damage to area close to CL is very small

Piping system as much as possible positioned close to the CL

Maximum penetration is the boundary of the safe area (r2) instead of CL

Way to simplify the investigation of progressive flooding

Negligible impact on attained index A: r3 = 1 – r2 is very small

No Safe Area

Investigation on progressive flooding for each damage case giving positive contribution to the attained index A

Fitting of valves to prevent progressive flooding

Maximum penetration is CL (or B/2)

Shadow of Tank concept

Damage case:

Damage in zone 1

Consequences:

Damage in space 1

Damage of pipe

Progressive flooding of space 3

Damage case:

Damage in zone 1

Consequences:

Damage in space 1

(No damage of pipe)

(No progressive flooding of space 3)

Damage case:

Damage in zone 2, up to r

Consequences:

Damage in space 2

Damage of pipe

Progressive flooding of space 3

Damage case:

Damage in zone 2

Consequences:

up to r1: damage in space 2 (no damage of pipe, no progressive flooding of space 3)

up to r2: damage in space 2, space 3 and pipe

OPENINGS, CONTROLS AND ESCAPE ROUTES

s = 0 (means: ship is not surviving), if position of

Air pipes, ventilators and openings closed by means of weathertight doors or hatch covers through which progressive flooding may take place

Horizontal evacuation route

is below the waterline at final equilibrium

Vertical escape hatch

Controls for the operation of watertight doors, equalisation devices, valves on piping or on ventilation ducts intended to maintain the integrity of watertight bulkheads above the bulkhead deck

Any part of piping or ventilation ducts not fitted with watertight means of closure, carried through a watertight boundary

is below the waterline in intermediate stages or at final equilibrium

OPENINGS, CONTROLS AND ESCAPE ROUTES

s not automatically 0 if position of

Air pipes, ventilators and openings closed by means of weathertight doors or hatch covers through which progressive flooding may take place

Horizontal evacuation route and vertical escape hatch

Controls for the operation of watertight doors, equalisation devices, valves on piping or on ventilation ducts intended to maintain the integrity of watertight bulkheads above the bulkhead deck

is above the V-lines

Any part of piping or ventilation ducts carried through a watertight boundary is fitted with valves able to prevent progressive flooding

SIMPLIFIED ANALYSIS – SUMMARY

V-lines concept

Safe Area concept

Pipes and valves are adjacent to a bulkhead (longitudinal/transverse) or deck

Provision: the separation distance is of the same order as the stiffening structure

Total cross sectional area of pipe < 710 mm2 (where possible)

Otherwise:

Investigation on progressive flooding for each damage case

If pipes and valves are outside the order of the stiffening structure, introduction of a gap or additional zone and investigation of progressive flooding

LOCATION OF VALVES AT BULKHEADS

Example:

SURVIVABILITY FACTORS

}{ ,,ite,intermedia imomifinali ssorsMINs sintermediate and smom not applicable to cargo ships but to passenger ships/SPS

S intermediate and S mom

→ S intermediate to be calculated for passenger ships only if :

► progressive flooding / equalization before cross flooding

greater than > 60 s

►Non watertight bulkheads restricting the immediate flow of water such as A class fire bulkheads, incenerator room, refrigerated spaces.

BOTTOM DAMAGE

Double bottom height [m] Bottom damage

h ≥ MIN{B/20,2}hmin = 0.76 NO

MINIMUM REQUIRED GM

pr, v-factors s-factor

Geometry of watertight

arrangement

Loading condition

Operationaltrim range ≤

0.5% Ls

Operational trimrange ≥ 0.5% Ls

p: longitudinal direction

r: transverse direction

v: vertical direction

Light draught

(dl)VCGl Actual Actual

Partial draught

(dp)VCGp 0 0

≠0 with steps≤1% Ls

Deepest draught

(ds)VCGs 0 0

≠0 with steps≤1% Ls

If the attained index A = pr v s satisfies the stability criteria of SOLAS 2009, the minimum GM-curve is drawn based on the chosen VCGs

Minimum GM-curve = envelope GM-curve covering calculations for different trim values

MINIMUM REQUIRED GM

2. SOLAS 92 and SOLAS 2009

► SOLAS 1992 (cargo ships)

Calculations for 2 draughts (deepest & partial)

No partial index requirements

Permeability for cargo holds is constant and equal to 0.70

Damage extent is up to CL

Calculations are performed at even keel (trim = 0)

► SOLAS 2009 (cargo and passenger ships)

Calculation for 3 draughts (deepest, light service & partial)

Partial indices Ai ≥ 0.5R

Permeability of cargo holds is function of draughts and cargo type

Damage extent is up to B/2

Calculations are performed for several trims if range of operational trims exceed +/- 0.5% Ls (subdivision length)

Thank you for your attention

probabilistic damage stability rules for cargo ships and sps (part b – solas 2009) paris, march...

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