PROBABILISTIC MODELING OF THE COLLISION.pptx

PROBABILISTIC MODELING OF
THE COLLISION FOR
STRIKING SHIP
SIMPLIFIED COLLISION MODEL (SIMCOL)
the extent of damage and local and global residual strength of ship
structures, after accidental events.
PROBABILISTIC DENSITY FUNCTIONS
RISK BASED SHIP DESIGN

Introduction
• Shipping is the fundamental as well as dominant means of transport for the world trade as
the Earth is almost covered by sea. Nearly 90.000 vessels of various size and more than 250
different types, specialized on cargo or passenger trade or both, serve for humanity.
• Yet shipping is the bulk delivery mechanism of international trade, and it plays a massive
part in humanity’s collective well being as billions of tons of raw materials and finished
goods are carried onboard ships between ports and port terminals economically, cleanly
and without mishap everyday.
• However, ships operate in a high-risk environment. In the age of precision navigation and
the satellite era, very many casualties still occur at sea. Even the available advanced and
sophisticated navigation instruments and the enhanced communication technologies have
been unable to halt shipping accidents.
• A shipping accident could be defined as “a usually sudden event or change, occurring
without intent or volition through carelessness, unawareness, ignorance, or
combination of causes and producing an unfortunate result.”
• Any shipping accident, whatever in nature, is an unfortunate event. Should it occur in a
confined area, like a channel or a strait where the traffic is heavy, several as well as serious
risks are likely to be faced. On the other hand, a major shipping accident becomes even
more critical by way of, say, water ingress thus possibly worsening the ship’s damage
stability if exacerbated by heavy weather or strong current. In some other accidents
however the issue becomes more “environmental” due to oil spillage.

• Ship collisions and grounding continue to occur regardless of continuous efforts to prevent such accidents. The
majority of the most catastrophic accidents of ships occurs due to collision and grounding. These accidents are
associated with areas of intense ship traffic and offshore operations such as oil production rigs.
• The injury caused by a ship collision accident not only causes oil spill and ship structure damage but also can
cause degradation of the marine environment, explosions, human losses, blocking of ships traffic and permanent
damage to the ship.
• According to Konopelko (1990), damages to the hull occur in 53% of ships’ accidents. On average, each ship of the
world fleet suffers hull damage once in 10 years with two ships out of one hundred damaged ships being lost.
• Besides holes, there are many damages of the hull that can be identified, such as rupture of elements
(infringement of integrity of a hull structure element due to exhaustion of its plastic deformation limit), cracks
(infringement of integrity of a hull structure element due to fatigue) or one-time overload in area of indents or
bulges resulting from buckling, as well as different kinds of deformations that are observed after accident.
• The assessment of the effect of incidents on the hull structure strength and ship survivability is based on the
damage dimensions, i.e, length, height, depth. The assessment of the effect of changed external loads on the hull
structure is based on data for the wind and wave conditions during the incident and the distance to a place of
refuge, which determines the greatest possible wave load. Therefore, statistical data for damages resulting from
incidents is necessary both in the design stage and in the process of developing operative methods to save the
ship.
• Due to hull damages, a number of events occur leading to reduction of the hull girder strength such as: loss of
longitudinals, asymmetric bending, warping and stress concentrations. The hull girder strength is preserved for
ships with small damages in stormy weather; ships with substantial damages but not exposed to wave loads; and
in cases when the ship’s crew and the salvage company actively and consistently fight for the ships’ survival.
Introduction

Crashworthiness and SIMCOL
• Shipping safety and marine pollution are inextricably linked, and the protection of the
environment from major disasters caused by ships sinking is rather complex.
• Efforts to protect the safety of ships and the sea environment are generally divided into two
classes: active and passive methods.
• Active methods assume that navigation equipment, crew training, and traffic control systems can
prevent accidents from taking place, whereas passive methods attempt to minimize the
consequences by, for instance, enhancing the crashworthiness of hull structures or improving
rescue operations.
• Ship safety following a collision accident event is bound to the collision phenomenon according to
the external dynamics and internal mechanics.
• The external dynamics concern the global motions of the ship during the collision event, whereas
the internal mechanics focus on the volume of the damaged material.
• In ship-to-ship collision events, the impact energy is mainly absorbed by large structural
deformations on the struck ship.
• If the outer shell of the struck ship resists the penetration of the striking ship without the inner
shell rupturing damage to passenger cargo can be minimized and oil spillage and flooding can be
avoided.
• the most promising simplified collisionanalysis alternative was to extend Minorsky’s original
analysis of high-energy collisions by including consideration of shell membrane energy
absorption.

METHOD FOR PREDICTING PROBALISTIC DAMAGE

Damage modelling and Risk based design
• Figure above illustrates the overall process proposed to predict probabilistic damage as a
function of ship structural design.
• (SIMCOL)model will be used to predict probabilistic collision damage extents given a
probabilistic description of collision scenarios.
• The process begins with a set of probabilities and probability density functions (pdfs) defining
possible collision scenarios.
• There are 3 major ship-to-ship collision classifications: puncture, raking and penetrating.
• Based on these pdfs, specific scenarios are selected in a Monte Carlo simulation, and, together
with a specific ship structural design, provide the necessary input to predict damage using
SIMCOL.
• sufficient data is generated to build a set of parametric equations relating probabilistic damage
extent to structural design. These parametric equations can then be used in oil outflow or
damage stability calculations.
• Knowledge of behavior on a global level only (i.e., total energy characteristics like the pioneering
Minorsky formula) is not sufficient. The designer needs detailed knowledge on the component
behavior (bulkheads, girders, plating, etc.) in order to optimize the design for accident loads.
• This mitigation of the collision consequences through designing against loss or collapse is called
Risk-Based-Design

www.safety-at-sea.co.uk
Risk is an Inherent Feature in the Maritime Industry!

The MACHINE model reflects the relationship between humans, technology and environmental elements

Illustration of different levels of failures that can cause
a collision
“The Septigon Model” by Thomas Koester
The scenario lack of awareness and the primary causes behind this
scenario

Marine accidents around the world
• Marine accidents have been occurring ever since men started to set sail. The custom of the trade
has been systematized over time, and later, by the middle of the 19th century, the navigational
standards emerged primarily as regulations for preventing collisions at sea. Since the beginning of
the last century, marine accidents have resulted in maritime industry efforts to improve ship
construction, ship systems reliability and onboard operations organization aiming at reduction of
marine accidents.
• However...

Number of accidents by accident type in the
Gulf of Finland

Marine Casualties & Incidents
• A Marine Casualty can be defined as any
event directly connected with the operations of a
ship that has resulted in any of the following
scenarios:
• the death of, loss of or serious injury to, a person
• the loss, or abandonment of a ship
• material damage to a ship or to
infrastructure
• the stranding or disabling of a ship,
involvement of a ship in a collision
marine
or the
• severe or potential for severe damage to the
environment, brought about by the damage of a
ship.
• A Marine Incident can be defined as any event, or
sequence of events, other than a marine casualty,
which has occurred directly in connection with the
operations of a ship that endangered, or, if not
corrected, would endanger the safety of the ship,
its occupants or any other person or the
environment
• It should be noted that neither a
marine casualty nor incident include a
deliberate act or omission, with the
intention to cause harm to the safety of
a ship, an individual or the
environment.

Classification of casualties according to severity
• Casualties according to their severity can be
classified among:
• Very Serious Casualties which are marine
casualties involving the total loss of the ship
or a death or severe damage to the
environment.
• Serious Casualties which are marine
casualties to ships which do not qualify as
very serious casualties and which involve for
example a fire, collision, grounding, heavy
weather damage, suspected hull defect, etc.,
which result in the ship being unfit to proceed
or pollution.
• Less Serious Casualties which are marine
casualties that don’t qualify as very serious
or serious casualties.
• Note: In Europe only 3.6% of all accidents
reported were classified as very serious,
while 18.1% were serious and 78.3% were
less serious and marine incidents

Safety onboard
Decline in total losses worldwide – 2006 to 2015
5
Large shipping losses have declined by 45%
over the past decade, driven by an increasingly
robust safety environment and self regulation.
Foundered (sunk or submerged) is the main cause of loss
accounting for half (50%) of all losses over the past decade.
Grounding is the second major cause (20%)
Fire is the third major cause (10%)
Collision is the fourth major cause (7.3%)
Source: Allianz Global Corporate & Specialty, Safety and Shipping Review 2015
Watertight doors are important in case of foundering,
grounding, collision and contact damages.

Lessons learned
From major accidents
1912 - The TITANIC collided with an iceberg,
which punctured the ship's hull and water
flooded in.
2007 - The Explorer, struck an unidentified
submerged object, reported to be ice, which
punctured the ship’s hull and water flooded in.
Lessons learned:
- Ship’s need to be designed so that the
flooding of compartments would not
jeopardize the buoyancy and stability of the
ship.
- Both Titanic and Explorer stayed afloat for
many hours due to the watertight
bulkheads, but eventually the ship sank.
Source: www.wikipedia.org
11
Source: www.wikipedia.org

Accidents by ship type in Europe
• The cargo ships category includes general and refrigerated cargo ships,
bulk carriers and vehicle carriers. The great majority of commercial ships
fall into this category. Consequently, it is no surprise that this was also by far
the biggest category for shipping accidents in and around EU.
• The tankers category includes tankers of all kinds, including oil, chemical
and gas tankers. Tankers are a high interest category, given that the Erika
(1999) and Prestige (2002) oil tanker disasters took place off the EU
coast, and that they extensively polluted a large proportion of the western
coastline.
• Container ship accidents can be particularly expensive in insurance terms.
The reason for this is that, tone for tone, ‘box ships’ often carry very high
value cargoes, and they are also increasing in size. Should an entire cargo
be lost or significantly damaged, the costs can be huge as even if a small
number of high value containers are lost overboard, the insurance cost can
be more than the loss of a general cargo ship. Added to this, larger and
larger ships are carrying more and more bunker fuel on board, so the
pollution risk that they pose is increasing
• The passenger ship category includes ferries and cruise ships. There was
no significant loss of life in passenger ship accidents during the last years,
but there were several accidents where the consequences could have been
a lot worse This continues to be a cause for concern, because there were
large numbers of passengers on the vessels, and any one of the accidents
could have become a disaster.

Types of casualty events
Casualty events are unwanted events in
which there was some kind of energy
release with impact on people and/or
ship including its equipment and its
cargo or environment.
• According to literature and experience
the major types of casualty events can
be classified among the following
categories:
• Capsizing/Listing:
is a casualty where the ship no longer
floats in the right side-up mode due to:
negative initial stability (negative meta-
centric height), or transversal shift of the
centre of gravity, or the impact of
external forces.
•Capsizing: when the ship is tipped over
until disabled;
•Listing: when the ship has a permanent
heel or angle of roll.

• Collision :
• Collision is a casualty
caused by ships striking or
being struck by another
ship, regardless of whether
the ships are underway,
anchored or moored. This
type of casualty event does
not include ships striking
underwater wrecks. The
collision can be with other
ship or with multiple ships
or ship not underway.

• Contact :
Contact is a casualty caused by ships
striking or being struck by an external object.
The objects can be: Floating object (cargo,
ice, other or unknown); Fixed object, but not
the sea bottom; or Flying object.
• Grounding/stranding :
occurs when a moving navigating ship,
either under command, under Power, or not
under command, Drift(ing), striking the sea
bottom, shore or underwater wrecks

Types of casualty events (cont.)
• Fire/explosion :
an uncontrolled ignition of
flammable chemicals and other
materials on board of a ship:
•Fire is the uncontrolled
process of combustion
characterized by heat or
smoke or flame or any
combination of these.
•Explosion is an uncontrolled
release of energy which causes a
pressure discontinuity or blast
wave.

Types of casualty events (cont.)
•Foundering:
Foundering is considered when the vessel
has sunk. Foundering should only be
regarded as the first casualty event if we
do not know the details of the flooding
which caused the vessel to founder. In the
chain of events foundering can be the last
casualty event in this case there is the
need to add accidental events.
•Flooding:
Flooding refers to a casualty when a
vessel takes water on board and can be:
-Progressive if the water flow is gradual
-Massive if the water flow is extensive.

• Hull failure :
Consists of a failure affecting the general structural strength of the ship.
• Loss of control: A total or temporary loss of the ability to operate or
manoeuvre the ship, failure of electric power, or to contain on board cargo or
other substances:
1. Loss of electrical power is the loss of the electrical supply to the ship or
facility;
2. Loss of propulsion power is the loss of propulsion because of machinery
failure;
3. Loss of directional control is the loss of the ability to steer the ship;
4. Loss of containment is an accidental spill or damage or loss of cargo or
other substances carried onboard a ship.
• Missing:
a casualty to a ship whose fate is undetermined with no information having
being received on the loss and whereabouts after a reasonable period of time.

• Non-accidental events:
Non accidental events are intentional events as a result of illegal or hostile acts therefore they are
not marine casualties or incidents.
• They are:
•Acts of war: any act, against a ship or the people on board, by a State that would effectively
terminate the normal international law of peacetime and activate the international law of war
•Criminal acts: any crime, including an act, omission, or possession under the laws of a State or
local government, which poses a substantial threat to people on board of a ship or to property (e.g.
terrorism, sabotage, piracy)
•Illegal discharge: an intentional discharge of polluting substances, oil or other noxious
substances, from ships
•Other casualties: Other intentional act that incur loss of or damage to a ship or environmental
damage or harm to people on board.

TYPES OF HULL DAMAGE
• According to Konopelko (1990), damages to the hull occur in 53% of ships’ accidents. On average, each ship
of the world fleet suffers hull damage once in 10 years with two-ships out of one hundred damaged ships
being lost.
• A great variety of incidents exist, such as collisions, grounding, explosions and fires severe storms, etc.
Therefore, a great variety of hull structure damages exist as well.
• Besides holes, there are many damages of the hull that can be identified, such as rupture of elements
(infringement of integrity of a hull structure element due to exhaustion of its plastic deformation limit),
cracks (infringement of integrity of a hull structure element due to fatigue) or one-time overload in area of
indents or bulges resulting from buckling, as well as different kinds of deformations that are observed after
accident.
• The assessment of the effect of incidents on the hull structure strength and ship survivability is based on
the damage dimensions, i.e, length, height, depth. The assessment of the effect of changed external loads
on the hull structure is based on data for the wind and wave conditions during the incident and the
distance to a place of refuge, which determines the greatest possible wave load. Therefore, statistical
data for damages resulting from incidents is necessary both in the design stage and in the process of
developing operative methods to save the ship
• The following types of residual deformations can be defined (see Fig. 1): indentions (local plate permanent
deflection in some areas between stiffeners); corrugation (permanent deflections of several adjacent areas
of plate between stiffeners); dents (local permanent deflection of a panel, which includes the plate and
supporting stiffeners); bulge (permanent deflection of the stiffener‘s web plate or the stiffener’s attached
plate)

Classification of
incidents’ damages of
vessel’s structures
influencing the hull
strength

Types of damage to ship’s hull in collisions and allisions
• holes - a hollow space in the ship’s hull with an opening on one side.
• rupture - of elements, an infringement of integrity of a hull structure element due to exhaustion of its plastic
deformation limit.
• cracks - infringement of integrity of a hull structure element due to fatigue) or one-time overload in area of
contact.
• Gashes – puncture leading to tear progressively can lead to water ingress but not enough to sink the vessel.
• Corrugation - permanent deflections of several adjacent areas of plate between stiffeners.
• Indentations, Indentions, - local plate permanent deflection in some areas between stiffeners).
• Indents - deformations resulting from buckling, as well as different kinds of deformations that are observed after
accident.
• Dents - local permanent deflection of a panel, which includes the plate and supporting
stiffeners,
• Bulges - permanent deflection of the stiffener‘s web plate or the stiffener’s attached plate.
• Scrapes – surface aberration leading to damage to paints and minor metal erosions not leading to any puncture.
residual deformations

Holes- a hollow space in something solid, as a
ship’s hull, with an opening on one side

Rupture - Rupture of longitudinals and plates

Cracks - in shell and framing a very narrow gap between
two things, eg. two hull plates, frames etc. or between two
parts of a thing

Dents, indentations
• DENT= a hollow in the surface of something which has been caused
by hitting or pressing it.
• INDENTATION = a shallow hole or cut in the surface or edge of
something.
• Two types of deformation modes are identified, namely local denting
and sliding deformation
• Denting of web girders
• Indentation of a bare plate (a) before fracture, (b) after fracture
• The deformation mode of local denting of web girders is widely
experienced during ship collision and grounding
• Shell plating is subjected to lateral indentation

Dents, indentations, a depression in the ship’s hull
made by a blow or by pressure in a collision or
allison, ice etc

Bulges
• a shallow hole or cut in the surface of the shell plating or ship's plates
developing after impact.
• a form of passive defense against naval torpedoes occasionally
employed in warship construction for protection, esp. in warships.
• in ship collision ... load becomes large enough, buckling occurs and
they develop local bulges the plate bulges out of the original plane of
the girder and folds to both sides in turn
•

Deflection, deformation, buckling
• DEFLECTION = the movement of a structure or structural member
when subjected to a load.
• DEFORMATION = the changing of form or shape of a plate or
structural member, as by stress.
• large plastic deformations and shape distortion of longitudinals
subjected to combined loads: lateral indentation, bending moment
and axial force.
• Buckling is characterized by a sudden sideways deflection of a
structural member such as brackets and stiffeners of longitudinals
• Deformation and buckling of transverses

Scratches, bruises and scrapes
SCRAPE = drag or pull a hard or sharp implement along
or across the ship’s side, bow or stern, shell plating etc.

Gashes
• GASH = a long deep cut in the surface of the ship’s hull (shell plating,
plates, etc.)

Other types and causes of damage
• Ramming damage – ramming, eg. a war a ship against another ship resulting in the destruction of the ships
involved)
• Slamming - the impact of the bottom structure of a ship onto the sea surface. It is mainly observed while
sailing in waves, when the bow raises from the water and subsequently impacts on it.
• Slamming induces extremely high loads to ship structures and is taken into consideration when designing
ships.
• Racking – (When a ship is rolling, the accelerations on the ship's structure are liable to cause distortion in the
transverse direction. The deck tends to move laterally relative to the bottom structure, and the shell on one
side to move vertically relative to the other side.
• Bending – The bending moment is the amount of bending caused to the ship's hull by external forces. For
example, The bending moment is the highest in the midship section when the ship's ends are supported by
crests of a wave ,known as `sagging' or `positive bending
• Pounding (When a ship is pitching, the bows often lift clear of the water and then slam down heavily onto
the sea, subjecting the forepart to severe pounding
• Panting – (Panting is an in and out motion of the plating which occurs at the end of the vessel due to the
variation in water pressure as the vessel pitches in a seaway. The effect is accentuated at the bow when
making headway)
• Buckling – ( happens when a force presses on a slender structure and makes it collapse, Collins Dict.)
(buckling is a mathematical instability that leads to a failure mode. When a structure is subjected to
compressive stress, buckling may occur. Buckling is characterized by a sudden sideways deflection of a
structural member. )

Investigation on design aspect of ship failures
• A statistical understanding of ocean waves has been fundamental to the design and
monitoring of marine and naval structures due to the random nature of the seas.
• Traditionally, ships have been designed to resist all loads expected to arise in their seagoing
environment. The objective in structural design has been to maintain a ship’s structural
integrity for normal operating conditions. A combination of the most severe loads is usually
selected as the nominal design load.
• Society expects that a cargo ship will deliver its cargo safely during a routine transit, but not
necessarily while transiting through a hurricane. Therefore, heavy weather guidance
systems exist.
• Public sensation increases each time there is a major loss of ships, cargo and life at sea, or
when there is oil pollution from damaged ships. This motivates the development of design
procedures and related analysis methods for accidental loads, in particular, the loads due to
ship collision or grounding accidents.
• A catastrophic failure is in the realm of societally acceptable risk and risk probability, but
the fiscal and operational cost of losing a capital asset like a Navy warship is still great.
• More specifically, the ability to understand the risk and frequency of catastrophic events
have been topics of interest in numerous fields. In a practical sense, ship designers write
specifications to deliver a product that will perform in the worst reasonable situation.

SHIP COLLISION RESEARCH HISTORY
• Minorsky (1959) made the first tentative to analyze the collision dynamics of two
ships initially in the context of transporting radioactive materials.
• His method examines the direct frontal collision on lateral hull of a struck ship,
considered as the worst condition by the author. The ships are considered as rigid
bodies, the collision is assumed to be completely inelastic and it is assumed linear
displacements of both ships, with no rotations.
• The dissipated energy estimation is based on the conservation of momentum, kinetic
energy and inelastic work. An added mass linked to the struck ship to include the
hydrodynamic effect was estimated in 40% of the struck ship mass.
• His model presents an empirical formulation derived from data of 26 actual ship to
ship collisions, which relates the volume of damaged structural steel to the energy
absorbed during the ship collision.
• His formula is generally considered valid only for high-energy collisions given a poor
correlation in low-energy cases.
• Woisin (1979) extended this formulation to include low-energy collisions and
Vaughan (1978) established a new formulation to relate energy with damaged
material volume including the area of tearing in his formulation.

• The basic principle of these methods is that both striking and struck ships are decomposed into simple
components such as plates, stiffeners, web frames, panels etc.
• The external dynamics commands the global movements of both ships and the deformation energy
absorbed in the collision is estimated by summing all the energies absorbed by each component
separately.
• The external dynamics commands the global movements of both ships and the deformation energy
absorbed in the collision is estimated by summing all the energies absorbed by each component
separately.
• The first methods are based on plastic membrane tension analysis for low-energy ship collisions before
failure, McDermott (1974) and Rosenblatt (1975) They assumed that only struck ship absorbs plastic
energy. Reckling (1981, 1983) provides an extension of this method in which striking bow is also allowed
to deform.
• Later, Petersen (1982) includes the hydrodynamics forces acting during the horizontal motion of the
striking ship by accomplishing added masses and damping in each section of the hull.
• These researches presented theoretical formulations to describe the dynamics of both ships. Blok and
Dekker (1979) and Blok et al. (1983) developed experiments involving scaled model of lateral ship
collision against a static protected jetty. This work focused in the analysis of the hydrodynamic mass
influence over the collision mode, collision speed and stiffness of the jetty fenders. The scaled ship was a
VLCC, carried at full load at velocities between 0.04 to 0.3 m/s.

• His procedure estimates the stress state of the ship components along the ship collision event. This
method only considers perpendicular collision, known contact force, non-rotational ship displacement,
additional masses (to represent the hydrodynamic effects); the struck ship was considered as an elastic
beam with uniform moment of inertia.
• The dynamic properties of the involved materials are not considered. This method allowed estimating the
critical velocity, i.e. the minimum striking ship velocity, to initiate failure in the target hull.
• A considerable collision energy absorbed by the striking bow was found, but the energy absorbed by the
membrane hull is actually not as significant as supposed. In general, this method gave a rough prediction
of a ship collision scenario to understand all the involved variables.
• Some works enhanced these methods by analyzing diverse aspects of these procedures. Hence, in the
study of Yang and Caldwell (1988), a kinematic method of plasticity to predict the crushing strength of a
bow structure in a ship collision event was applied. It is estimated by summing all the energy dissipated
by each structural element.
• The energy absorbed by the axial crumpling of plate elements in the bow structure was the most
significant part of all the dissipated collision energy as observed also in experimental tests. An increasing
of the mean crushing force due high strain rates effects was detected. Then, Samuelides and Frieze (1989)
developed a numerical algorithm in which both dynamic structural and transient hydrodynamic responses
during a ship collision event are coupled in the time-step solution.
• So the dynamic stiffness of the struck ship and the force yielded by the fluid are continuously updated
during the simulation. The non-linearities and strain rate sensitivity of the material are also considered
and the critical speed of collision was estimated. Egge and Böckenhauer (1991) evaluated the absorbed
plastic deformation energy using the ultimate load method for low-energy ship collision analysis

• In the study of Parks and Ammerman (1996) the range of validity of Minorsky model depending on the
absorbed energy in a ship collision event is discussed and the inclusion of the basic failure mode of
Akita (1972) is recommended.
• Suzuki et al. (2000) also evaluate the efficacy of the Minorsky model by using a simplified rigid plastic
analysis of the collision between two tanker ships, one ten times bigger than the other, and
demonstrate that Minorsky gives an incorrect estimation of the energy in case of striking or struck ship
is much stronger than the other.
• Finally, Reardon and Sprung (1996) enhanced the formulation of Minorsky and extended for low-
energy collisions by adding other 16 actual ship collisions data.
• Pedersen and Zhang (1999) developed a ship collision simulation employing an analytical method to
evaluate the plastic deformation and rupture of the ship structure based on deformation mechanisms
coupled with the external dynamic formulations and a collision probability analysis.
• The entire structure was divided in axial crushing modes L, T and X, which contains its plastic
deformation behavior and the non-linear solution, and for the material failure three well-known
criteria were reviewed: tensile tearing, transverse shear and energy density failure mode. Then,
Pedersen et al. (2000) evaluated the ship structure damage using this analytical method.
• The striking bow is considered as a deformable structure and also as a rigid body. This research
demonstrated that only in some cases the assumption of the striking bow as a rigid body is true and
also that transversely stiffened bows are significantly softer than the longitudinally stiffened ones.
• In the same year, Pedersen and Zhang (2000) demonstrated that the assumption of the collision
damages, when normalized by the main dimensions of the ship, having the same probability density
distributions, in spite of the structural design and ship size, is an error.

• Actually, normalized collision damage depends on the size of the ship, as verified by actual statistical
data. For instance, larger ships or the use of more resistant naval steel shows damage relatively smaller.
• Some institutions made efforts to systematize these analytical methods. For that reason, here are also
reviewed some numerical codes to couple both external dynamics and internal mechanics analyses of a
ship collision event.
• The SIMCOL algorithm was originally developed by Crake (1995) and Brown (2002). It uses the time-
domain simultaneous analysis of external dynamics and internal mechanics of a ship collision event.
• Initially, the external dynamics is based in the formulations of Hutchison for three degrees of freedom
(1986) and the internal mechanics on the works of Rosenblatt (1975) and Reardon and Sprung (1996).
• However, this model assumes that, after the inelastic collision, both ships move together as a single
body. Some years later, Pedersen and Zhang (1998) and Zhang (1999) also developed similar generalized
formulations for the external dynamics collision of two ships, a ship with a floating log, a ship with a rigid
wall and a ship with an offshore structure.
• Based on further research, test runs and the need to include a broad range of design and scenario
variables, improvements were progressively made by Chen (2000), Brown and Chen (2002), Brown and
Sajdak (2004) and Vakkalanka (2000) such as introducing friction forces, lateral deformation of the web
frames (considered previously as rigid), the vertical extent of the striking bow as well as analyzing the
importance of considering a deformable bow of the striking ship.
• This software allows analyses with different ship velocities, collision angles and longitudinal position of
the struck ship. Thus, Brown et al. (2002) joined the SIMCOL software and Monte Carlo optimization
method to minimize the collision damage using a sample of 1000 ship collision scenarios. The probability
of damage penetration and crashworthiness were estimated.

• Brown and Chen (2002) used these external dynamic formulations to develop probability density functions to
describe the damage in struck ship in ship collision. The type of ships and their speeds, collision angle and the
striking ship displacement are treated as independent variables. Other parameters are fixed based in the
statistics of worldwide ship data
• Their mathematical models include also friction at the contact point so sliding motion is included. Pedersen
and Li (2009) analyzed the elastic energy that can be stored in elastic hull vibrations during a ship collision
applying the external dynamic formulations seen previously.
• The elastic vibration of the ship hull is estimated using a simple uniform free beam model to represent the
global bending vibration of the struck ship during the ship collision.
• Only the striking ship is still considered as a rigid body. The elastic energy absorbed by the bending vibration of
struck ship can vary from 1 to 6% depending of the characteristics of ships and contact point.
• The results showed that the added mass coefficients obtained experimentally are higher and vary depending
whether the ship collision is eccentric or not, Fig. 3a. Tabri et al. (2008) also developed ship collision
experiments involving scaled models. The ship motion and the contact force were measured during the
experiments, Fig. 3b.
• The motion analysis. showed that ship motion was nearly linear up to the contact force reached its maximum.
During contact, a small angular motion was observed and it increased significantly after contact was lost. The
results of scaled model tests, large-scale experiments and an analytical model were compared.
• The mass ratio resulted to be more significant than the collision velocity and structural response, in the case of
symmetry collisions, for the estimation of the dissipated deformation energy. Tabri et al. (2009b) validated the
scenario of four ship collisions by comparing with experimental results from scaled ship models.

• Their evaluation involves an external dynamic model of a nonsymmetric ship collisions event
considering six degrees of freedom for each ship, an arbitrary impact location and collision angle. The
contact force is evaluated by the integral of the surface resistance at the contact interface.
• Tabri et al. (2008, 2009a) studied the effect of the large forces generated by the sloshing in ballast
tanks of the struck ship. This sloshing model simulates the liquid cargo using an equivalent mass-
spring-damper system.
• The dynamic generalized model takes into account all aspects of the previous model including the
elastic bending of the struck ship and the sloshing model. When compared with experimental tests, the
results reveal the significance of the sloshing effect, which stored 32% of the kinetic impact energy
instead of transferring it to the ship structure.
• Also Zhang and Suzuki (2007) analyzed the structural response of a struck liquid cargo-filled tank during
a ship collision event to model the fluid-structure interaction in liquid-filled cargo tank.
• Three different numerical methods were compared: Lagrangian–Eulerian finite elements, Lagrangian
finite elements and linear sloshing model, revealing significant differences on the motion and
structural response. Lagrangian–Eulerian resulted to be the most efficient method given its relative low
computational processing cost.
• Awal and Islam (2008) investigated the ship capsizing due to collision with another ship in calm water
using a dynamic modeling with rigid ships. The mathematical model is validated by comparing the
kinetic energy losses obtained by other authors. The maximum amplitude of the roll motion is related
to parameters such as striking velocity, coefficient of restitution, collision angle, collision time and
vertical position of hitting point to find the survivability associated to the collision event.

• Structural strength in collision, grounding or internal accidents (such as an explosion) has
attracted very little attention. computational tools have allowed designers to replicate
model testing, ship systems performance, and model ship process in a digital space.
• By integrating these decision support tools into the design process, it is now feasible for
designers and decision makers to evaluate a much wider design space than ever before.
• The wave groups approach presented in this work provides a deeper understanding of the
probability of extreme events in ship motion and loading conditions to inform functional
requirements of for a risk-based design approach.
• The final phase of the study is a discussion on the application of this approach for
quantifying event statistics using on systems engineering technical feasibility and barriers
of entry for achieving a near-real-time risk decision support system based on wave groups.
• In the past decades, many attempts have been made to measure incident wave
characteristics at sea; however, all attempts have been overwhelmed by the non-linearities
of the sea and the ship's structure.
• Protection of a ship and the cargo it carries from damages incurred by accidents, though an
essential issue in the design of watercraft, has been focused on subdividing a ship into
compartments. National and international standards (Load Line, MARPOL, SOLAS,
Classification Societies’ Rules) have established requirements for watertight bulkheads and
subdivision.

What is design?
• No exact definition
- The application of knowledge/science to solve a problem
- Knowledge synthesis
- Optimization
- Engineering

Design models
Any design task involves the
determination of a design model
Always an abstraction (generalization)
of an artefact
• Approximate representation
Should be limited to areas of interest
• The level of detail (model fidelity) should
be adapted to the design task
• A higher level of detail/complexity not
always better
Picture: http://akerarctic.fi/
Picture: https://mec.ee

Design terminology
Design model
Parameters
Variable(s) Constraints
Performance assessment
Design objectives
External uncertainty
Internal uncertainty

Prescriptive regulations
• Ship design is traditionally regulated by
prescriptive design rules and regulations
- Dates back to a time when ship design was more art
than science
• Often determined based on experience
- Determined in the form space
• Determine the required means of achieving safety
objectives
- Alternative names
• Deterministic rules, i.e., rules that require a specific
solution assumed to provide a specific deterministic
performance
• Specification rules, i.e., rules that specify the required
solution
SOLAS (The International
Convention for the Safety
of Life at Sea ) convention
(1st version)
Picture: Willy Stöwer
(Re)design
Build
T
est
Evaluate

Prescriptive regulations
Examples of prescriptive rules:
• To avoid structural failure
- Min scantlings, corrosion margins, design loads,
etc.
• To avoid loss of stability
- GZ-curve requirements, etc.
• To mitigate the consequences of a collision
- Longitudinal bulkheads, etc.
• To mitigate the consequences of grounding
- Double bottom requirements
• To mitigate the consequences of a fire
- Max allowed fire zone size, etc.
Prescriptive rules  Prescriptive-based
design
Additional examples of
prescriptive rules:

Pros of prescriptive-based design
• Quick and straight-forward to apply, and to verify compliance
- Well suited for “standard” designs
• Jenkins: “For vessels which are standard and where there is high confidence that the
prescriptive regime achieves a good level of safety, there is little reason to change from a
wholly prescriptive approach”
• Based on real life experience (what works)  small risk for ending up
with a very bad design (at least for standard designs)

Cons of presciptive-based design
• Limited feasible design space
- Rules act as design constraints, potentially preventing new innovative solutions
• The efficiency of the solution depends on the efficiency of the rules
- Traditionally failed to be proactive
• Rule development traditionally driven by individual catastrophic events, often in response to
public outrage
• Cost efficiency not always considered
- Often determined based on existing designs (empirical data) the rules might not be
effective/optimal for new types of designs/operations
- The level of safety provided by the rules not known (the objective is generally not
defined)  responsibility transferred to rule maker  Does not encourage “safety
thinking”
• Does not encourage safety above the minimum required level

Trend towards goal-based regulations
Driving factors
• Multiple weaknesses of prescriptive-based design
• Ever increasing level of knowledge, improving performance assessment
tools, and more powerful computers  Ever improving ability to assess
various types of ship performance
• Larger, more complex ships
• Strong competition, low profit margins  Design optimization
• Increased “safety thinking” (corporate social responsibility)
- Accidents are bad for business, safety pays off

Goal-based regulations
• Goal-based rules
- Design criteria determined in the
function space in terms of goals and
functional requirements (FRs) to meet
the goals
- Defines what the goal is that has to be
achieved
• E.g. the maximum evacuation time is 10
min
- Alternative name: performance-based
rules
• Goal-based rules  Goal-based
design (GBD)
Figure: Jenkins 2012

Risk-based regulations
• Risk-based rules: goals and FRs determined in risk terms
- E.g. the maximum accepted individual risk is 10−3
- Alternative name: probabilistic-rules
• Risk-based rules Risk-based design (RBD)
- Can be considered as a subcategory of goal-based design
- SADEFOR: “RBD is a formalised methodology that integrates systematically risk
assessment in the design process with prevention/reduction of risk embedded as a
design objective, alongside “conventional” design objectives”
- Broader definition of RBD: “Design under uncertainty”

Goal/Risk-based design
Design model
Parameters
Variable(s) Constraints
Performance assessment
Design objectives
External uncertainty
Internal uncertainty
Risk assessment / Safety
performance assessment
Rules and regulations

What is risk-based ship design and approval?
A new methodology integrating
probabilistic / risk-based
approaches in the design process
for ships and ship systems
Safety is one additional design
objective along traditional
objectives such as speed and cargo
capacity
Risk is used as measure to evaluate
effectiveness of design changes
with respect to safety
Risk-based approval is the process
of approving risk-based designed
ships and their intended operation
Safety through Innovation

Motivations to use risk-based approaches
Implement a new and safe solution
which cannot be approved today
- example: alternative design and
arrangements for fire safety
Optimise an existing solution which
is in range of being approved today
- example: probabilistic damage
stability
Both ideas need
- a new design approach that
includes safety as objective
- a modern regulatory framework
McNeece
ColorLine

Expected benefits
Owners and operators benefit from
improved economics of novel solutions
- example: more cabins with balcony
on a cruise ship with larger than
prescribed lifeboats
Yards and equipment manufacturers
benefit from sustained competitive
position
- example: offer innovative layouts
for cruise ship super structures
- example: offer new ship systems
with increased safety performance
- example: reduce production costs
with new fire insulation layout
With proof of safety compliance
becoming more complex, patenting new
solutions becomes more attractive.
Chantiers de l’Atlantique
http://www.mes.co.jp

The RBD – Road map
Innovative ship designs
year 1
Risk-based design (concept, methodology,
framework, risk-cost models, design environment)
FSA studies
Concepts for safety-critical technologies
Risk-based regulatory framework
Final designs
Approval in principle
Training
Dissemination and exploitation
year 2 year 3 year 4
Demo
Demo
Methods
and Tools
Regulatory
Framework
Application
Supporting
Actions
Selection of the
two best designs
Safety-performance prediction tools
Benchmarking

Pros of goal/risk-based design
• ”Any” solution that meet the goal(s) and the related functional
requirement(s) is acceptable  Expanded feasible design space
• Safety becomes measurable  Possible to determine goals, application
of the most cost-efficient risk control measures
• Proactive risk management= not limited to past experience
• Safety responsibility is transferred from the regulator to the designer
(owner)  Encourages “safety thinking”

Cons of goal/risk-based design
Time and resource consuming (requires a significant
investment)
• Only motivated if significant potential for improvement
Risk of misleading performance assessments
• Need to provide confidence to the regulators regarding the presented
risk assessment and related risk control measures
• Larger, more expensive ships increased risk
- The robustness of modelling validation, data used and so on needs to reflect the
potential scale of consequences

Cons of goal/risk-based design
Both passive (design) and active (operational) risk control
measures considered  The ship need to be operated as
planned throughout its lifetime
• Challenging for instance in the case of change of ownership  New
safety culture, different (lower) level of competence
- Sufficient documentation needed to explain the rational used when optimizing the
design

Challenges and for risk-based design
Availability of advanced simulation
software and experimental tools to
predict ship and system
performance at sea in extreme and
accidental conditions
Determination of involved
uncertainty through tool validation
and benchmarking
Harmonisation of risk models to
ensure consistent application
Parametric modelling of ships and
integration of tools to fully exploit
optimisation potentials

Challenges for risk-based approval
Formal establishment of risk-based
regulatory framework at IMO linked
to Goal-based Standards and the
Safety-Level Approach
Uniform interpretation of modern
regulations to ensure consistent
application to increase ship safety
Agreed top-level risk acceptance
criteria at IMO
Derivation of lower-level functional
risk acceptance criteria through
continuous submission of Formal
Safety Assessment studies
Fairplay
Peterswerft

Expected effects on ship operation
Operation must reflect any relevant
assumptions used in the design and
approval process
Special training needed for owners
and crew to learn the risk-based
approaches involved
Clear and concise documentation in
an agreed format needed onboard
the vessel to ensure that PSC does
not lead to vessels being delayed or
detained
Integration with other risk-based
approaches in ship operation like
ISM, risk-based inspection and
reliability-centred maintenance
Fairplay
Fairplay

73
• Can the extensive knowledge acquired during the
design development be used to manage
operational (residual) risk and to address ER?
73
RBD Impimplementation Example
LCRM (Operation): Oasis of the Seas Pilot Study

• The International Maritime Organization (IMO) took first steps in 2009 to shift the
maritime industry from prescriptive design standards to a risk-based system.
• This shift was driven by the conflict between technological advances in manufacturing
and computation with a design envelope that was limited by regulation.
• This foray into Risk-Based Ship Design (RBSD), the quantification of extreme events
statistics on ship design.
• A ship may collapse after an accident because of inadequate longitudinal strength.
However, the consequences of an accident on a ship’s strength are seldom
investigated. Although there are some papers published on the residual strength of
damaged ship hulls, this field still remains unexplored.
• Traditionally, quantifying the risk using physics-based models has been a resource-
intensive process to develop a method of characterizing the statistics of the rare events
at a fraction of the computational cost.
• Typical designs of 67 commercial ships, including 21 double hull tankers, 18 bulk
carriers, 22 single hull tankers and six container carriers, which have lost portions of
bottom shell plating and side shell plating, are analyzed to obtain such simple
equations for predicting residual strength of damaged ships.

• The proportion of catastrophic failures to the number of vessels at sea has shrunk in the
past half century because of rule-based design standards and improved quality assurance
practices.
• A catastrophic failure is in the realm of societally acceptable risk and risk probability, but
the fiscal and operational cost of losing a capital asset like a Navy warship is still great.
• Risk that was acceptable 70 years ago is not necessarily acceptable today. whether a
more efficient and accurate approach to the quantification of extreme events in ship
design exists?
• How would it affect ship design, ship operations, and ongoing science? With overall
objective of improving the safety of the ships structure.
• Historically, in the maritime industry, regulations were a reaction to major accidents or
disasters. In many cases, these regulations resulted from an ad hoc safety assessment
process seeking to reduce public and political pressures for action. Such processes favor
quick solutions over a rigorous technical analysis that explores the cost versus benefits of
solutions.
• Worse, this reactive approach has made the regulation system more complex as
amendments are continually made, thus leaving limited room for innovation and
advancement in the industry.

• The transition to risk-based approaches began with probabilistic damage
stability standards in the 1960s, but took decades to be introduced by the
International Convention for the Safety of Life at Sea (SOLAS).
• Project HARDER (1999 to 2003) investigated elements of the traditional
approach and proposed a new formulation for the probabilistic damage stability
employing enhanced computational models and statistical methods.
• The final recommendations from this study were adopted in 2005, prompting a
four-year study, Project SAFEDOR (Design, Operation and Regulation for Safety),
across a consortium of fifty-two European organizations to incorporate risk-
based approaches into ship design, operations, and regulations.
• The maritime industry, in one way or another, has been caught between
two main design drivers:
• (1) economic drivers to push more cargo faster and cheaper; and
• (2) societal drivers to reduce losses at sea and to do less harm to the environment.
• Under these pressures and limitations of traditional prescriptive regulations,
ship designs quickly reached a sub-optimum optimal.

Requirements
Final Concept
Design Solution
Logistics Business
Needed functions, basic
“Perceived” Risk
services, costs, earning potential, all accident categories
etc…
Lo
P
ne
grp
fo
ro
rm
m
ea
na
nd
c
e
e
, podF
pu
ro
n
pc
ut
ls
io
io
n
na
, litR
yegulatiS
on
a
sf:e
stu
y
bd
R
iv
u
is
lie
os
n,
Expected safety level for
double hull, LSA, fire
protection, etc.
low NOx/SOx, high speed,
manoeuvrability, etc.
Owner
Time
Contract
Design Today: Rules-Based Design
Concept
Design Studies
Concept
Design Studies
Yard
Experience, T
alent! Available Knowledge
Design Tools
& methods
Damage stability and
survival capaility Trim, intact stability
Cost estimates
Light ship weight and
capacities
Proportions and Final design Powering and propulsion
preliminary powering arrangement
Lines and body plan Structure arrangement
and strength
Hydrostatics and General arrangement
hull shape Hull arrangement and
Dillon, 1969 and Erichsen 1989 freeboard
Logbased WP1
Input (Module 1 to 6)
survival capaility
Cost estimates
Logbased WP1
Lines and body plan
Hydrostatics and
hull shape
Dillon, 1969 and Erichsen 1989
Hull arrangement and
freeboard
General arrangement
Powering and propulsion
arrangement
capacities
Structure arrangement
and strength
Trim, intact stability
Final design
Proportions and
preliminary powering

Safety is treated as Rule Compliance
 This can not nurture a safety culture!
Quality
Evasion Culture Safety Culture
Compliance Culture
%

Safety is treated as Constraint
 Safety eats on innovation potential
Innovation
Functionality
Performance
Safety rules
potential
Design Solutions Space

SOLAS 90 and SOLAS 2009 are meant to provide
the same safety level for damage stability of
passenger ships  they do not!
Safety Level of a Design is unknown
SOLAS 2009
SOLAS’ 90 Ships
Ships

• Incompatibility of design and performance
evaluation tools, time limitations, lack of an
integrated design environment; all hinder
design optimisation in the design process.
• Lack of a formal optimisation process also
implies that life-cycle issues (future costs /
earning potential) are not being taken
“explicitly” into account in design decision-
making.
 optimal design solutions are not possible!
Meeting Safety Expectations is left to Chance

Shipping Society
Science &
T
echnology
Safety
Need for change
• escalation in size
• specialisation
• higher speed
• construction materials
• over-capacity
• greater complexity
• more information
• less time
• competition
• manning
• ageing fleet
• public expectation
for higher safety
• Increased public
regard for human life
and environment
• media coverage
• political pressures
• phenomenal progress
• rapid technological
change
• better technical
capabilities
• innovation potential
• cost-effective safety
The Changing Face of Ship Safety
Safety Drivers
12

Traditional approaches to safety (rules-based)
are experiential and with change happening
faster than experience is gained, the "safety
system" is unsustainable.
Need for a New Safety System
The Changing Face of Ship Safety
Need for Change

Requirements
Concept
Design Studies
Final Concept
Design Solution
Logistics Business “Perceived” Risk
Needed functions, basic Expected safety level for
services, costs, earning potential, all accident categories
Time
Contract
Experience, T
alent!
survival capaility Trim, intact stability
Cost estimates
capacities
Proportions and Final design Powering and propulsion
preliminary powering arrangement
Lines and body plan Structure arrangement
and strength
Hydrostatics and General arrangement
hull shape Hull arrangement and
Dillon, 1969 and Erichsen 1989 freeboard
Logbased WP1
Logbased WP1
Lines and body plan
Hydrostatics and
hull shape
Dillon, 1969 and Erichsen 1989
Hull arrangement and
freeboard
General arrangement
arrangement
etc…
Lo
P
ne
grp
fo
ro
rm
m
ea
na
nd
c
e
e
, podF
pu
ro
n
pc
ut
ls
io
io
n
na
, litR
yegulatiS
on
a
sf:e
stu
y
S
bd
R
a
iv
f
u
ie
s
lie
to
y
s
n,
double hull, L
O
Sb
Aj
,e
fic
retives
protection, etc.
low NOx/SOx, high speed,
manoeuvrability, etc.
Owner
Yard
of “
St
S
ruca
ture
fa
e
rra
t
ny
geme
P
nt erformance”
b
and
y
stre
F
ngth
irst-Principles
preliminary powering
Tools
Available Knowledge
Des
A
ig
d
nd
Ti
o
to
io
ls
nal
Functi methods
quirements
survival capaility
Cost estimates
Power
V
ing
e
an
r
d
i
pr
f
o
i
pu
c
lsi
a
on
tion
capacities
Trim, intact stability
Final design
Proportions and
onal Re
Design Criteria
Risk-Based Design
Safety is an Objective
15

RBD High-Level Framework
RBD  Design with known safety level
Integrated Design Environment
[Software Platform]
Evaluation of ship
performance
Requirements and
Constraints
Ship functions and
performance criteria
Performance
Expectations
Design safety goals
Definition of design safety goa
and functional requirements / preferences
Identification of hazards
Identification of possible design solutions
(focus on accident prevention)
Identific
relevant
ation of critical functions, systems
key safety parameters
ation of critical/design scenarios
g, fire, system failure, etc)
and
Identific
(floodin
Risk Analysis
How probable? How serious?
(Level of detail depends on design stage)
Risk Assessment
Implementation of risk control measures
(focus on preventing occurrence of accidents)
(i)
(v)
(iii)
(ii)
SAFETY ASSESSMENT PROCEDURE
safety
performance
Design
Decision-
making
echnical company/society
SHIP DESIGN
risk
t
performance
costs
aesthetics
values, preferences
Systems, components,
hardware
(design solution)
fitness for purpose
feasibility
(iv)
Meeting
Safety
Objectives
Satisfying
Design
Goals
16

Sustainable System for Coninuous Improvement
• A formal process to address risk at the
design stage (risk reduction / mitigation), in
operation (managing residual risk) and
ultimately in accidents (crisis management),
ensuring in all cases an acceptable level of
risk (safety assurance).
• A formal process facilitates measurement of
safety performance, which constitutes the
basis for continuous improvement (Virtuous
Cycle).
17
Life-Cycle Risk Management

Life-Cycle Risk Management
Design, Construction (SLE), Operation (MRR)
Safety
Policy
Feedback and
Improvement
Performance
Measurement
Implementation
HAZID, QRA, RA, CBA
Safety
Management
Strategy / Plan
Safety
Management
Organisation
SMS

19
RBD Impimplementation
Motivation
Alternative Design and Arrangements
 local level
SOLAS Ch. I, Regulation 5 (certain systems - excemptions)
SOLAS Ch. II, Regulation 17 (Fire Safety)
SOLAS Ch. III, Regulation 38 (LSA Code)
SOLAS Ch. I, Regulation 4 (Damage Stability – equivalence)
(RBD) Design Optimisation
 ship/platform level
 HSC Code / SRtP / SPS Code / Polar Code
 Safety level
 Goal-Based Standards

• Establishing a Design team
• Preliminary (qualitative) analysis
– Definition of scope
– Development of casualty scenarios
– Development of trial alternative designs
• Quantitative analysis
– Quantification of design scenarios
– Development of Performance criteria
– Evaluation of trial alternative designs
• Documentation
Preliminary
Approval
Final
Approval
20
RBD Impimplementation – AD&A
IMO Guidelines – Overview

Goal/risk-based maritime regulations
Important goal/risk based maritime regulations include
• Goal-based standards (GBS)
• Formal safety assessment
• Safety equivalence
• Probabilistic damage stability
• Probabilistic oil outflow performance
• Polar Code

Goal-based standards (GBS)
• High-level standards and procedures that are to be met through
• regulations, rules and standards for ship
• Rules for rules
- Rules for how to develop goal-based rules/standards
• GBS are comprised of at least
- One goal
- Functional requirement(s) associated with that goal
- Instruments necessary for demonstrating and verifying that the associated rules and
• regulations for ships conform to the goals and functional requirements.

• The basic principles to be applicable to all goal-based
• standards/regulations developed by IMO are:
- Broad, over-arching safety, environmental and/or security standards that ships are required to
meet during their lifecycle
- The required level to be achieved by the requirements applied by class societies and
• other recognized organizations, Administrations and IMO
- Clear, demonstrable, verifiable, long standing, implementable and achievable, irrespective
of ship design and technology
- Specific enough in order not to be open to differing interpretations
• IMO instruments using the GBS approach are the Polar Code, IGF Code,
and Goal-based ship construction standards for bulk carriers and oil
tankers

Goals (Tier 1)
• Goals are high-level objectives to be
met. A goal should address the
issue(s) of concern and reflect the
required level of safety.
- Examples (top-level goals)
• No accidents leading to total ship loss (collisions,
groundings, stranding, fires, etc.)
• No loss of human life due to ship related accidents
• Low impact to the environment (no air emissions,
low noise, low wash)
• Minimum impact to the environment in case of a
ship accident

Functional requirements (Tier II)
• FRs provide the criteria to be satisfied in
order to meet the goals
• Once a goal has been set, FRs are
defined. They should cover all
functions/areas necessary to meet the
goal, and be developed based on
experience, an assessment of existing
regulations, and/or systematic analysis
of relevant hazards

Example of how goal-based functional
requirements for ship structure
could be derived

Verification of conformity (Tier III)
• Instruments necessary for demonstrating
and verifying that the associated rules and
regulations for ships conform to the goals
and functional requirements.
• The verification process should be
transparent and result in a consistent
outcome irrespective of the evaluator

Verification of conformity (Tier III)
• Verification of conformity should
- be based on techniques varying from first
principle models to historic data
- be based on analyses using proven and
established technology
- be based on defined clear qualitative and
quantitative criteria with a preference of
quantitative values
- check whether currently known modes and
causes of failure are covered
- be verified by independent auditors and/or
appropriate IMO organs, as decided by IMO

Rules and regulations for ships (Tier
IV)
• Rules and regulations for ships are
the detailed requirements developed
by IMO, national Administrations
and/or classification societies and
applied by national Administrations
and/or classification societies acting as
recognized organizations in order to
meet the goals and functional
requirements.

Industry practices and standards
(Tier V)
• Industry standards, codes of practice
and safety and quality systems for
shipbuilding, ship operation,
maintenance, training, manning, etc.,
may be incorporated into or referenced
in the rules/regulations

Monitoring
• Monitoring is a method of evaluating
the effectiveness of goals (Tier I),
functional requirements (Tier II), rules
and regulations (Tier IV) and
standards/practices (Tier V) as well as
attempting to identify risks not addressed
in the initial rules/regulations
development.
• In order to verify that the risk of shipping
is kept as low as reasonably practicable,
GBS framework should be continuously
monitored and systematically analysed.

Quantification of Extreme Events
• Since the IMO adopted RBSD as a regulatory framework, the maritime industry
has gradually shifted to better quantify and predict rare and
catastrophic events.
• The challenge with this approach, lies in modeling these systems of systems. In
many cases, the physics we use are computationally demanding and the cost at
stake continues to grow.
• To observe such an event, the direct Monte Carlo approach would have to
produce 500,000 hours of simulation. Further, to achieve the level of statistical
significance, this event should be observed no less than 10 times, totaling
5,000,000 hours of simulations for a single combination of speed a heading.
Quickly, the size of this analysis becomes insurmountable even for the most
advanced computer clusters.
• The alternative to capturing statistics of these extreme events, extreme value
theory (EVT) fit by mathematical models. The precept for EVT is that rare events
are similar in their behavior based on some nonlinear physical property.

Mitigation Analysis
Systems Availability
Evacuation & Rescue
Accident Causality Analysis
Casualty Threshold /Safe Return to Port
Consequence Analysis
Flooding survivability analysis
Scenarios
Scenarios Flooding survivability analysis
Scenarios Fire safety analysis
Collision
Grounding/
Stranding
Fire Systems Availability
Evacuation & Rescue
Systems Availability
Evacuation & Rescue
Safety Level (Total Risk)
RBD Impimplementation – PSS
IMO Framework for Passenger Ship Safety

Example Loss Scenario
Flooding | Collision
Water ingress (hull breach)
Loss of stability
Abandonment
Navigation failure
prevention
mitigation
34

Safety measures and risk assessments
• The safety measures of maritime transportation were influenced by several groups:
ship designer, ship operators and maritime societies.
The ship designers influence by safe design of bridge layout, navigational equipments, engine
and steering control, maneuverability, and redundancy.
The ship operators influence by safe operation of ship speed, manning levels, crew attitude
and training, and maintenance.
The maritime societies influence by safe aiding and monitoring of vessel traffic systems, pilots,
traffic lanes, aids to navigation (i.e. AIS, GPS) and safety inspection procedures.
• However, the effectiveness of maritime safety measures are eventually evaluated
under rigorous navigation and collision conditions with respect to the vessel
operator’s decisions.
• The analysis of vessel navigation information will help to detect collision situations
and to assess collision risk. The collision risk should be evaluated in real-time by
vessels and/or Vessel Traffic Monitoring and Information Systems (VTMIS) in order
to guarantee safety and security measures in maritime transportation.

• The mathematical formulation of collision detection between two vessels
can be divided in two methods: Closest Point Approach method (CPA) that
is a two dimensional method (2D) and Predicted Area of Danger method
(PAD) that is a three dimensional method (3D).
• The CPA method consists of calculating the shortest distance between two
vessels and assessing the collision risk that could be predicted with respect
to each vessel domain. However, the CPA method alone cannot be
implemented in the evaluation process of collision risk, since it does not
consider the vessel size, course and speed variations.
• The PAD method consists of modeling one vessel possible trajectories as
an inverted cone and the other vessel trajectory as an inverted cylinder,
being the region of both object intersections categorized into the
Predicted Area of Danger. Both vessels’ size, course and speed conditions
could be integrated into the geometry of the objects of navigational
trajectories in this study .
Safety measures and risk assessments

RiskPLL  EN FN i
i1
Nmax
FN N  frN i
iN
Nmax
1E-05
1E-04
1E-03
1E-02
1E-01
1E+00
1 10 100
Fatalities [N]
1000 10000
Frequency
of
N
or
more
fatalities
per
ship
year
35
Risk Model

fr N fr hz  pr N hz 
nhz

j1
N j
j
hz
N
36
Risk Model

Aft peak bulkhead Machinery space bulkhead Collision bulkhead
New requirements for Minor damage concept (still deterministic) for passenger
double bottom vessels, but no specific requirements on location of watertight
subdivision. Required index to be met
Aft peak bulkhead Machinery space bulkhead Collision bulkhead
New requirements for
double bottom
Minor damage concept (still deterministic) for passenger
vessels, but no specific requirements on location of watertight
subdivision. Required index to be met
A > R
n
 ( pi  si ) =
i=1
38
Statutory Assessment – SOLAS 2009

Formal safety assessment (FSA)
An approach for the determination of new or modified rules at IMO
using risk analyses and cost benefit assessments
• Transparent and systematic comparison of various risk control options
“FSA is a structured and
systematic methodology,
aimed at enhancing
maritime safety, including
protection of life, health, the
marine environment and
property by using risk
analysis and cost benefit
assessment” (IMO)

Risk acceptance criteria
• The max accepted individual risk
• The max accepted societal risk
• The max expenditure to avoid a statistical
fatality in accordance with the principle of As
Low As Reasonably Practicable (ALARP)
- Not static, approx. USD 1.5-3 million

The acceptable individual risk depends on if the risk is
taken voluntarily or involuntarily.
Risk acceptance criteria proposed by Norway
• Max tolerable risk for workers (crew member), 10−3 per
year
• Max tolerable risk for public (passenger), 10−4 per year
Costs with regard to individual and societal risks could
be expressed in terms of the cost of averting fatality
(cost per-life-saved, value of life)
• The IMO recommended indices for presentation of RCOs
cost effectiveness in relation to safety of life are Gross
Cost of Averting a Fatality (GCAF) and Net Cost of
Averting a Fatality (NCAF)
• Values will depend on geographic location, local economy,
and type of activity and public tolerance of risk

Formal safety assessment
Limited application of FSA
• Probably because the FSA process is highly technical and complex,
taking approx. 1 year to complete
FSA has to date not been applied on environmental risk control
measures
- No agreed on environmental risk measures or criteria

Safety equivalence
General principle
• Any solution may deviate from the prescriptive requirements if the
alternative design meet the intent of the goal and functional requirements
concerned and provide an equivalent level of safety as the prescriptive
design
To prove equivalency, a design must to be analyzed, evaluated, and
approved in accordance with IMO guidelines
Also referred to as “alternative design”
Challenges
• How to assess and compare the safety performance of the prescriptive
solution with that of the alternative solutions
• Prerequisites
- Agreed on and comparable safety performance measures
- Safety performance assessment methods

Safety equivalence
Alternative design and arrangements
for fire safety
• Prescriptive rule
- Max allowed length of fire zone: 40 m
• Application of the principle of safety
equivalence enables large open public
spaces
• Equivalency demonstrated by advanced
numerical fire simulations + evacuation
simulations
Photo: Color line

Objective: to ensure sufficient damage stability
• A ship's ability to survive various flooding scenarios is quantified in
terms of the subdivision index A (degree of subdivision)
A=σ 𝑝𝑖 𝑠𝑖 , A ≥ 𝑅
𝑝𝑖 = the probability that the compartment or group of compartments under consideration may be
flooded
𝑠𝑖 = the probability of survival after flooding of the compartment or group of compartments in
question (calculated based on a ship’s GZ curve for the damage scenario in question)
R= minimum required subdivision
• Determined based on real-life accidents
• Different designs with the same index value are considered equally safe
• R is determined based on ships whose damage stability is considered
satisfactory  Not related to any specific level of safety risk!
• Operational aspects (active measures) not considered
Propabilistic damage stability

Propabilistic oil outflow performance
Objective: to limit accidental oil outflow
• A ship's ability in limiting oil outflow is quantified in terms of a
measure referred to as oil outflow performance
- Also referred to as pollution prevention index
• Determined based on a probabilistic approach utilizing damage
statistics of real life incidents
- Related calculations are complex and extensive and therefore carried out using
dedicated software tools
• Weakness: the index does not relate to any explicit level of
environmental risk
- The IMO has not agreed on any environmental risk measures or criteria

Regulations
MARPOL Annex I-Regulations for the
Prevention of Pollution by Oil,
• In terms of ship design, the most important
environmental convention
• Requires all tankers above 5,000 DWT to be
fitted with a double hull
• Regulates the maximum allowed tank size

Regulations
Double hull generally considered the most
efficient type of accidental discharge
prevention system
• Weaknesses related to ship stability,
maintenance costs, and fatigue
• Found to be cost-inefficient
IMO's Probabilistic Oil Outflow Method
• Effectiveness quantified in terms of a vessel’s
oil outflow performance (ENV safety index)
determined based on a probabilistic approach
utilizing damage statistics
- An alternative design can be accepted if its oil outflow
performance is at least as good as that of a standard
design
- Oil outflow performance not related to any actual ENV
risk measure
Alternative design:
The Coulombi Egg concept

Regulations - Proposals
Cost of Averting a Tonne of oil Spilt (CATS)
• Cost-effectiveness criteria for considered risk control options
• Risk reducing measures are to be implemented if:
CATS < F ∗ Ctot
F = Insurance factor ≈ 1.5
Ctot = Total costs of an ocurred spill ≈ USD 40,000 (global average)
Weaknesses / critisism
• The consequence of one tonne of spilled oil is highly dependent on the
where the release takes place
• The US Marine Board indicated that the relationship between spill size and
environmental consequence is nonlinear
- Per-tonne clean-up cost decreases with spill size  discount for large spills

Based on the NORSOK standard
• Recovery time as criteria
- The maximum acceptable frequency of an accidental event is specified as a
percentage of the related recovery time
• Suitable for a specific area
Environmental damage category Recovery time
Insignificant < 1 month
Minor 1 month – 1 year
Moderate 2 – 3 years
Considerable 3-10 years
Serious > 10 years

Source: SAFEDOR
project, D.4.5.2- Risk
Evaluation Criteria

Collision risk assessment
• The proposed detection process consists of the derivation of relative navigation
trajectory and course-speed vector between two vessels that could use to
evaluate prior collision/near collision conditions.
The proposed collision detection process consists of following steps;
the observation of both vessels’ positions;
the estimation of both vessels’ velocities, accelerations and navigational trajectories;
the calculation of the vessel relative navigational trajectory and relative course-speed
vector of a selected vessel with respect to other vessel.
• The observation of relative navigation trajectory and relative course-speed
vector of the other vessel could use to improve the detection of collision
situations.
• The relative navigation trajectory could illustrate as a conventional bearing
observation situation.
• However, the relative course-speed vector of the other vessel can be used as an
additional tool that could improve the collision detection process.

what extent the respondents considered the primary causes contribute to the scenario lack of awareness

• It is assumed that both vessels’ positions are measured by conventional AIS
and GPS systems.
• However, there are many challenges faced by the systems during its
position measurements:
The first, the AIS and GPS position signals can be associated with sensor noise and/or
system errors, therefore the measurements accuracy would be compromised.
The second, the vessels are maneuvering under varying sea conditions; the own and
target vessel kinematics and dynamics could be associated with time-varying
parameter conditions.
• The extended Kalman filter, one of the well known estimation algorithms,
to overcome previous challenges and to estimate accurate vessel states is
proposed.
• The main contribution of this study can be summarized as the estimation
of vessel’s relative navigation trajectory and course-speed vector based on
parameter uncertainties in vessel maneuvering that can be used to detect
potential collision situations among vessels.

• The main objective of the CRA module is to evaluate the
collision risk and the expected time until collision of each
target vessel with respect to vessel navigation.
• The CRA module will transfer collision risk information to
the SAF (Sequential Action Formation)module for
collision avoidance actions.
• The mathematical formulation of detection of collision
situations is presented in this section. Therefore, the
section is divided into three sections of derivation of
system model, formulation of measurement model and
Extended Kalman filter.
• In the system model section, a mathematical model for a two
vessel collision situation is derived.
• In the measurement model section, the observations of
available vessel states are formulated.
• In the extended Kalman filter section, the procedure for the
estimation of relative vessel navigation trajectory and course-
speed vector is presented.

Two vessel collision situation
1. The own vessel, the vessel that is equipped with
the INS, is located in point O (xo, yo).
2. The target vessel, the vessel that needs to be
avoided, is located at point A (xa, ya).
3. The own vessel speed and course conditions are
represented by Vo and χo respectively.
4. The target vessel speed and course conditions are
represented by Va and χa respectively.
5. The own and target vessels’ instantaneous radius
of curvature of maneuvering are presented by Ro
and Ra.
6. The x and y velocity components of the own and
target vessels are presented by vxo, vyo,vxa and
vya respectively.
7. The own and target vessels’ normal and
tangential acceleration components are
presented by ano, ato, ana and ata respectively.
8. The collision encounter angle between vessels is
presented by θa.

Types of collisions
• Ship-ship collision occurs if a ship strikes another ship.
• Collisions can be divided into crossing, merging, head-on, and overtaking
collisions
• Ship collisions are normally classified into two groups, namely
ship-ship collisions and head-on collisions.
• Ship-ship collision represents a situation in which the bow of a striking ship
collides with the side structure of another struck (collided) ship.
• Contrary to the case of grounding, it is not essential to divide collisions into
powered and drifting collisions as in a collision situation there are two
ships involved and it is enough that one of the ships is able to avoid the
other.
• Thus, mechanical failures are not an important reason for ship-ship
collisions.
• Head-on collision typically represents a situation in which the bow of a
vessel collides with fixed rigid walls such as piers and bridge abutments.

Collision Risk Assessment
• One of the outcomes of these studies is the concept of risk-based design (RBD)
for ships where the major criterion for RBD is the ability of a ship to survive in
damage conditions.
• Although a general framework for this purpose is provided by the International
Maritime Organisation, few researchers have approached this topic in a holistic
manner.
• Most of the models utilize the concept of a fault tree (FT) or event tree (ET)
following Boolean logic, which in some cases may not fully reflect reality, as the
events being analysed may take more than just two states.
• Furthermore FT and ET allow one-way inference, which in turn may limit their
applicability in the field of systematic risk mitigation and management.
• Probabilistic Risk Assessment (PRA) in complex sociotechnical systems, where
alternative, hybrid approaches have been proposed, utilising FT, ET and
Bayesian Belief Networks.

1. A fundamental stage of any risk analysis, and one which affects all the following stages, is scenario identification. This
includes proper description of the knowledge about an MTS and its behaviour in a certain situation (e.g. an accident
befalling a ship).
2. This means that a risk framework should be capable of reflecting the right variables in the right way, considering the
associated uncertainty along with a clear definition of the initial assumptions.
3. When it comes to describing the evolution of the accident the framework attempts to capture the causality, which makes
the framework systematic. Its modular nature allows continuous improvement and adaptation to various locations and
conditions, thus making its transferable.
4. Most of the existing models adopted for risk assessment in maritime transportation are defined in a spatio-temporal,
stochastic framework; However, these models often disregard causal relationships between input variables (e.g. ship size,
collision speed, collision angle, relative striking location, and weather) and output variables (e.g. the ship capsizing).
5. These relations are hidden under single probabilities (e.g. the probability of flooding given a collision or the probability of a
severe collision) or probability density functions (e.g. a PDF representing the extent of the damage caused by a collision).
6. This way of representing data disregards the causality in the scenario, and therefore substantial elements of risk analysis
are missed, i.e. the links among variables and their mutual relationship, This ultimately increases the uncertainty of the
model. some of the above-mentioned shortcomings of the existing models can be addressed by applying BBNs to a risk-
analysis framework.
7. First, BBNs allow multi-scenario thinking, which not only focuses on an undesired end event (a collision) but also provides
insight into the process of the evolution of an accident. Second, BBNs structure reflects the causality in the process being
analysed allowing further knowledge-based decision-making. Third, BBNs can efficiently handle the uncertainties about
variables and the uncertainties about the relations among variables, and represent those in the outcome.
Bayesian Belief Networks (BBNs)

• BBNs allow reasoning in both directions, pointing out the most vulnerable nodes and the most effective ways of
improving the outcome of the model. Thus the back-propagation of the probabilities can be utilised in the
recommendation phase of risk assessment.
• Moreover, BBNs allow the adaptation of a formal risk definition following the well-founded idea of triplet given by
Kaplan. Triplet attempts to answer the following questions: what can go wrong in the system?; how likely is it that it
will go wrong ?; and what are the consequences if the assumed scenario occurs?
• A formal, and well-established definition of risk in decision analysis is “a condition under which it is possible both to
define a comprehensive set of all possible outcomes and to resolve a discrete set of probabilities across this array of
outcomes”.
• By adopting this framework, and BBNs as tools for probabilistic modeling, it is possible to apply modified risk
perspective of Kaplan, which for this paper reads as follows: -
• where S stands for a set of scenarios which comprises the same chain of events, described by the same explanatory
variables but the variables and their relations can be described by adopting different assumptions. background
knowledge of the process being analyzed – BK
• L is a set of likelihoods corresponding to the set of consequences C, for a given set of scenarios (S) and given
combination of anticipated assumptions governing the model parameters.
1. The effect of changes in the predefined relations between variables, called likelihood functions (LFs), can be
quantified. This is accomplished by performing a so-called influence analysis.
2. This analysis is especially important in the case of LFs which are not based on solid foundations. All of these analyses
allow BBNs-based risk framework to represent the level of available BK about the domain in question in a transparent
and systematic way.
Kaplans Risk Assessment

Quantitative collision risk assessment

Likelihood – L
• In the field of risk analysis in engineering systems, three methods of
interpreting the likelihood are usually followed: the relative frequency,
subjective probability and a mixture of these called the probability of
frequency;
• The numbers derived from various sources are combined with the use of BBNs,
which encode the probability density function governing a set of random
variables by determining a set of conditional probability functions (CPFs).
• Each variable is annotated with a CPF, which represents the probability of the
variable given the values of its parents in the graph:
• The CPF describes all the conditional probabilities for all the possible
combinations of the states of the parent nodes.
• If a node does not have parents, its CPF reduces to an unconditional
probability function, also referred to as a prior probability of that variable.

Conditional probability function
• From a mathematical viewpoint, classical BBNs are a pair N = {G, P}, where
G =(V,E) is a directed acyclic graph (DAG) with its nodes (V) and edges (E),
while P is a set of probability distributions of V.
• Therefore, BBNs representing a set of variables and their dependencies
consist of two parts, namely a quantitative (P) and a qualitative (G).
• Therefore, a network N = {G, P}, is an efficient representation of a joint
probability distribution P(V) over V, given the structure of G following the
formula: -
• The CPFs are relevant elements of the framework; first, they govern the
flow of knowledge through the framework, and second, they constitute a
link between the qualitative and quantitative parts of the framework.

Risk framework definition
• The aim of the proposed framework it to estimate the risk in MTS,
focusing on selected accidental scenarios that, ultimately, lead to the loss
of a struck ship.
• These scenarios are
I. the inner hull of the ship that is struck is breached and consequent flooding is
experienced; this can result further in the loss of the ship;
II. the ship that is struck has no significant hull damage; however, the ship is
disabled and drifts, thus experiencing significant rolling as a result of wave and
wind action, which can result further in the ship capsizing.
• The loss of the ship is expected if two consecutive limits are exceeded,
namely crashworthiness and stability.

• The five-step procedure defining the risk framework as follows: -
1. defining what to model;
2. defining the variables;
3. developing the qualitative part of the framework;
4. developing the quantitative part of the framework;
5. validating the framework.
• Subsequently the corresponding probabilities of the limits being exceeded given
the traffic and environmental conditions are evaluated on the basis of the model
presented here.
• For this purposes the following general factors are taken into consideration: the
composition of the maritime traffic in the sea area being analysed, the collision
dynamics, hydrodynamics of the ship and her loading conditions.
• Ultimately, the cumulative number of fatalities (N) resulting from an accident is
modelled utilising the concept of the rate of fatalities. This rate is determined taking
into account time for evacuating a ship and time for a ship to capsize.
• All these, along with the associated probabilities (P) for a given number of fatalities,
are finally depicted in a F N diagram, which can be considered as a risk picture.
Risk framework definition

Defining the variables
• The causality in the process of open-sea collision that is being analysed by defining the relevant
variables and constructing logical relations between them.
• Thus the framework consists of four major parts, covering the following areas:
i. collision-relevant parameters;
ii. capsizing-relevant parameters;
iii. the response to an accident;
iv. quantification of the consequences.
• The collision relevant parameters are obtained from a maritime traffic simulator, which utilizes
AIS data and accident statistics.
• Ship capsizing is conditional upon various events, of which the most relevant are : -
i. the collision speed and angle for the given ship mass ratios, leading to the rupture of the inner hull of a struck ship
conditional upon a collision;
ii. the extent of damage leading to the significant ingress of water, conditional upon the inner hull being ruptured;
iii. the hydrometeorological conditions contributing to the ship capsizing given the significant ingress of water;
iv. the maximum roll angle at which a disabled, intact ship capsizes.
• To reduce the number of probabilities that need to be determined to evaluate the framework,
the parametric probability distributions (PPDs) for the variables were used.
• These provide simple computation rules for obtaining the required probabilities

Collision probability
• The probability of a collision between two ships in the open sea in which the ship
is struck by another ship is estimated by means of the dynamic maritime traffic
simulator (DMTS),
• The input to the DMTS is taken from the Automatic Identification System (AIS),
augmented with harbour statistics concerning the cargo types that are traded.
• The annual frequency of such an accident, attributing equal chances of being
struck and striking to a ship involved in a collision equals 0.1. This means that a
collision in which a ship is involved would happen every 10 years.
• The annual frequency of an accident in the open-sea in which a ship is struck are
obtained, 0.07 from the DMTS, and 0.0075 from the accident statistics.
• Therefore it is assumed that the “true frequency” might fall between these two
numbers, and they are considered as limits for a uniform distribution estimating
the probability of an open-sea collision.

• First, the initial value of this parameter is obtained from the DMTS, and then it is considered as
the input value for the statistical models, thus arriving at the actual collision speed. There are
several different
statistical models for estimating the collision speed and collision angle;
• Therefore, this concept is applied here with the following assumptions:
1. the velocity of a striking ship A follows a uniform distribution for velocities between zero and 75% of her
initial speed, then the probability decreases triangularly to zero at her initial speed.
2. the velocity of a struck ship B is approximated by a triangular distribution with the most likely value equal
to zero and a maximum value equal to her initial speed;
3. the initial speed values of A and B are obtained from the DMTS;
4. the collision angle, defined as the difference in the headings of two colliding ships, is uniformly
distributed between 10◦ and 170◦.
• Then, applying the four-step random sampling Monte Carlo procedure, the distribution of the
actual collision speed is estimated as follows: -
1. sample the initial speed of a striking ship obtained from the MDTS, then use it as an input to determine
the appropriate uniform-triangular distribution; subsequently sample the speed from this distribution
randomly, and store it as VA
2. sample the initial speed of a struck ship obtained from the MDTS and use it as an input to the triangular
distribution; subsequently sample the speed from this distribution randomly, and store it as VB;
3. randomly sample the collision angle α from the uniform distribution;
Collision probability

Collision consequence
 CONSEQUENCE CANNOT ONLY BE RELATED TO THE STRUCTURAL DAMAGE OF THE VESSEL.
 HUMAN SAFETY, EFFECT ON ENVIRONMENT, ECONOMIC CONSEQUNCE, REPUTATION OF SHIPPING COMPANY,
AMOUNT OF OIL OUTFLOW MUST BE INCLUDED IN ANALYSIS.

Collision consequence
• The consequences of a collision, can be separated into
consequences for the vessel as minor damages, severe damage
or total loss, consequences for human safety or for the
environment.
• From these may follow consequences for the shipping company
in the form of a bad reputation or economic consequences.
• The individual consequences are listed as the following: -
1) Human safety
2) Consequences for the vessel
3) Environmental consequences
4) Consequences of reputation
5) Economic consequences

Human safety
• Human safety is normally not directly affected by a collision, but in the case of
severe damage to the vessel, the vessel may capsize and lives may be lost.
• Especially, collisions involving passenger ships may result in a high risk. Minor
injuries may also arise during the collision, mainly due to de-acceleration.
• Loss of lives or injuries may result in a bad reputation for the vessel and the
company and have consequences.
• It has been, however, seen in the risk assessment and calculation of fatality that
during the ship loss with sinkage in the case of progressive flooding and in case of
low time to sink or collapse the probability rate of fatalities are quiet high.
• In fact in case of capsize either due asymmetrical flooding and /or due to the
overturning in the wind and waves due to loss of stability and dead ship condition
due to machinery damage the the probability rate of fatalities are highest.

PROBABILISTIC MODELING OF THE COLLISION.pptx

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