CONFIDENTIAL: for internal use only

BASIC COURSE FOR SURVEYORS - Module 7

HULL STRUCTURE
Rev. 1

Section 6 – Elements of strength of materials

Section 1 – Introduction
pag 33
pag 4

Section 2 – Reference Documentation
6.1 Elasticity pag 33
pag 5
6.2 Stress and strain pag 34
2.1 The SOLAS Convention pag 5
6.2.1 Tension and compression pag 34

Section 3 – Definitions pag 6
6.2.2 Shear pag 36
3.1 Geometry of the ship pag 6
6.3 Beams pag 36
3.2 Structural parts of the ship pag 7
6.3.1 Bending in Beams pag 38
3.3 Ship Dimensions pag 7
6.3.2 Bending stress in a beam pag 39
3.4 Ship and cargo weights pag 8
6.3.3 Shear stress in a beam pag 41
3.5 Pictures pag 8
6.3.4 Normal Stress pag 41

Section 4 – Ship Arrangement pag 14
6.4 Plates pag 42
4.1 Main zones of the ship pag 14
6.4.1 Plating with stiffening pag 42

Section 7 – Materials
4.1.1 Cargo Area pag 14
pag 44
4.1.2 Fore part pag 15
7.1 General pag 44
4.1.3 Machinery space pag 15
7.2 Steel pag 44
4.1.4 Aft part pag 16
7.2.1 Steel Types pag 44
4.1.5 Superstructure pag 17
7.2.2 Steel Grades pag 45

Section 8 – Loads
4.1.6 Exceptions pag 17
pag 47

Section 5 – Ship Structure pag 18
8.1 Environmental loads pag 47
5.1 Main structural boundaries of the ship pag 18
8.2 Ship weight and cargo pag 47
5.1.1 External boundaries pag 18
8.3 Loading Conditions pag 48

Section 9 – Hull girder strength 49

5.1.2 Internal subdivisions pag 19
pag
5.1.3 Decks pag 19
9.1 The ship as a beam pag 49
5.1.4 Side and bottom pag 19
9.2 Loads on the ship girder in still water pag 49
5.1.5 Inner bottom pag 20
9.2.1 Weight and buoyancy for a barge in still water pag 50
5.1.6 Inner side pag 21
9.2.2 Weight and buoyancy for a ship in still water pag 50
5.1.7 Longitudinal Bulkheads pag 22
9.3 Loads on the ship girder in waves pag 51
5.1.8 Transversal Bulkheads pag 22
9.3.1 Weight and buoyancy for a barge on waves pag 51
5.1.9 Particular structures for Bulk Carriers pag 23
9.3.2 Weight and buoyancy for a ship in waves pag 52
5.1.10 Openings pag 24
9.4 Verification pag 52
5.2 Structure components pag 25
9.4.1 The ship’ girder’s section pag 52
5.2.1 General pag 25

Section 10 – Verification of ship scantlings pag 54
5.2.2 Plating pag 26
10.1 Navigation notation load reduction coefficients pag 54
5.2.3 Stiffeners pag 28
10.1.1 Navigation notations pag 54
5.2.4 Primary supporting members pag 29
10.2 Structural analyses based on the “net scantling concept” pag 55
5.2.5 Pillars pag 30
10.2.1 Use of the “net scantling concept” at the design stage pag 55
5.2.6 Corrugated Bulkheads pag 31
 10.2.2 Use of the “net scantling concept” during the survey 11.8 Superstructures pag 75

Section 12 – Structure of different ship types

of ships in service pag 56
pag 76
10.3 Strength criteria and limit states pag 57
12.1 Passenger ships pag 76
10.3.1 General pag 57
12.2 Ro-ro ships pag 77
10.3.2 Yielding limit state pag 58
12.3 General dry cargo ships pag 78
10.3.3 Strength of plating under lateral loads pag 59
12.4 Ships for carrying cargo in bulk pag 79
10.3.4 Buckling limit state pag 59
12.4.1 Bulk Carriers pag 79
10.3.5 Ultimate strength pag 59
12.4.2 Ore Carriers pag 82
10.3.6 Fatigue pag 60
12.4.3 Obo pag 82

Section 11 – Ship structures in detail pag 61
12.5 Tankers pag 83
11.1 Bottom (Double Bottom / Single Bottom) pag 61
12.6 Dry cargo/ Container pag 84
11.1.1 Structural Arrangement pag 61
12.7 Container SHIP pag 85
11.1.2 Bilge Keel pag 62
12.8 Liquefied gas carriers pag 86
11.1.3 Possible structural problems pag 64
12.9 Refrigerated vessels pag 88
11.2 Side pag 64
11.2.1 Structural Arrangement pag 64
11.2.2 Sheer Strake pag 64
11.2.3 Brackets pag 65
11.2.4 Openings pag 65
11.2.5 Possible structural problems pag 65
11.3 Watertight bulkheads pag 65
11.3.1 Structural Arrangement pag 65
11.3.2 Openings pag 66
11.3.3 Watertight doors pag 66
11.4 Decks pag 66
11.4.1 Structural Arrangement pag 66
11.4.2 Openings pag 67
11.4.3 Possible structural problems pag 67
11.5 Fore structure pag 68
11.5.1 Loads and relevant reinforcements pag 68
11.5.2 Stem pag 69
11.5.3 Bow thrusters pag 69
11.5.4 Equipment pag 70
11.5.5 Forecastle pag 70
11.6 Aft structure pag 71
11.6.1 Structural Arrangement pag 71
11.7 Engine room pag 73
Section 1:
INTRODUCTION

This course material is intended to give a basic knowledge regarding the ship structure and the way it is verified by
RINA for class purposes.
For this scope, some basic concepts of strength of materials will also be introduced, in order to help those who do
not have a deep knowledge on this subject.
This course material is not intended to be exhaustive or to replace the reading and understanding of RINA Rules.

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Section 2:
REFERENCE DOCUMENTATION

2.1 THE SOLAS CONVENTION

[1] RINA Rules for the classification of Ships:
• Part A - Classification and Surveys
• Part B - Hull and Stability*
• Part D - Materials and Welding
• Part E - Service Notations
• Part F - Additional Class Notations

[2] Common Structural Rules for Bulk Carriers

[3] Common Structural Rules for Oil Tankers

[4] IACS Recommendation 82: Surveyor’s Glossary

[5] IACS Recommendation 47: Shipbuilding and Repair Quality Standard

[6] IACS Recommendation 76: Guidelines for Surveys, Assessment and Repair of Hull Structure - Bulk Carriers

[7] IACS Recommendation 84: Guidelines for Surveys, Assessment and Repair of Hull Structures – Container
Ships

[8] IACS Recommendation 96: Guidelines for Surveys, Assessment and Repair of Hull Structures - Double Hull
Oil Tankers

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Section 3:
DEFINITIONS

This Chapter gives some essential definitions related to this Module.

3.1 GEOMETRY OF THE SHIP

After Perpendicular (AP): The vertical line at the point of intersection of the LWL and the centreline of the
rudderstock.
Afterbody: Portion of a ship’s hull abaft midships.
Baseline (BL): imaginary line used as a reference for vertical distances. It is usually located at the bottom of the
hull.
Bow: The forward of the ship
Forebody: Portion of a ship’s hull forward midships.
Forward Perpendicular (FP): The vertical line at the point of intersection of the LWL and the forward end of the
immersed part of the ship’s hull.
Hull: The structural body of a ship including shell plating, framing, decks and bulkheads.
Load Waterline (LWL): The waterline at which the ship will float when loaded to a certain design draft
Midships: The point midway between the forward and after perpendiculars.
Port :The left side of the ship when looking forward
Starboard: The right side of the ship when looking forward
Stern: The after end of the ship
Superstructure: The parts of the ship structure situated above the main deck.
Waterline: The intersection of the moulded surface with a horizontal plane at a given height above the base line.

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DEFINITIONS

3.2 STRUCTURAL PARTS OF THE SHIP

Bulkhead: Vertical structure subdividing the hull into separate compartments. Bulkheads can be transversal or
longitudinal.
Deck: A structure extending horizontally (or almost horizontally) from one side of a ship to the other, and generally
subdividing the ship in horizontal zones (only the Inner Bottom has the same function but is not a “Deck”).
Double Bottom: Compartments at the bottom of a ship between inner bottom and the shell plating, used for fresh
water, ballast water, fuel oil, etc. Space under the Inner Bottom
Double Side: compartment adjacent to the side, delimited in horizontal direction by the side, the inner side and in
the vertical direction by a deck and the inner bottom or the bottom.
Inner Bottom: (almost) horizontal structure over the bottom, forming the top of the double bottom (sometimes
indicated as “Tank Top”)

Inner side: vertical structure adjacent to the side, forming one delimiting bulkhead for the double side.

Midship Section: A transverse section exactly half way between the F.P. and the A.P.

Shell plating: The plates forming the outer side and bottom skin of the hull

3.3 SHIP DIMENSIONS

Bilge Radius: The radius of the circular arc forming the bilge.
Breadth at Loaded Waterline (BWL): Maximum moulded breadth at the loaded waterline.

Depth Moulded (D): The vertical distance at amidships from the baseline to the underside of the plating of the
main deck.

Draught (T): The vertical distance from the waterline at any point on the hull to the bottom of the ship.

Freeboard (f): The vertical distance from the waterline to the deck at side. The freeboard is equal to the difference
between the depth at side and the draught at any point along the ship.

Length Between Perpendiculars (LBP): The distance measured parallel to the base at the level of the design
waterline from the after perpendicular to the forward perpendicular.
Length of Waterline (LWL): The waterline at which the ship will float when fully loaded.

Length Overall (LOA): The total length of the ship from one end to the other, including bow and stern overhangs.

Maximum Beam or Breadth (BM): Extreme beam (breadth), from outside to outside of the shell plating.

Moulded Beam or Breadth (B): The distance from the inside of plating on one side to a similar point on the other
side measured at the broadest part of the ship.
Trim: The difference between the draughts forward and aft.

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Section 3:
DEFINITIONS

3.4 SHIP AND CARGO WEIGHTS

Deadweight: The difference between the displacement and the lightweight is the deadweight tonnage which is the
sum of the weight of cargo, fuel, lubricating oil, fresh water, stores, passengers and baggage, crew and their
effects: DWT=W C+W F+W LO+W FO+ W PAS+W LUG+WCREW+W STORE.
Light ship weight: the lightweight tonnage of a ship is the sum of all fixed weights, i.e. hull, machinery, outfit and
permanent equipment (LS=WS+WM+WO)

Moulded Displacement: The displacement of a ship based on moulded dimensions

Total Displacement: Moulded displacement modified by adding the thickness of shell plating and the volume of
appendages. It is the weight of water that is displaced by the volume of the hull measured on the outer surface of
the shell plating below the waterline. Displacement tonnage of a vessel can be obtained directly by multiplying its
underwater volume by the density of water.

3.5 PICTURES

The following figures present the ship’s nomenclature on sections of different ship types:

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DEFINITIONS

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DEFINITIONS

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DEFINITIONS

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DEFINITIONS

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DEFINITIONS

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Section 4:
SHIP ARRANGEMENT

(“Anatomy of the ship”).

In this Chapter we will examine the general layout of a ship, the main structural zones, the delimiting structures, the
openings.

4.1 MAIN ZONES OF THE SHIP

The following zones, as indicated in the Figure, may be identified in a cargo ship:
Figure 11 - Main zones of a cargo ship

Superstructure

Fore

Aft
Cargo area

Engine room
Each of these zones has a different treatment and specific requirements in the Rules. A more detailed description
of these zones is provided in Chapter 0”SHIP STRUCTURES IN DETAIL”

4.1.1 Cargo area

The cargo area may be sub divided (by transversal bulkheads) in Holds or Tanks or may be a single area (e.g. the
garage in ro-ro ships). The cargo area is not dedicated exclusively to the cargo. Actually, many compartments used
to contain ballast or other liquids are included in the cargo area.

Figure 22 - cargo area

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4.1.2 Fore part

The collision bulkhead, the deck and the shell delimit the fore part of the ship.
Typically the fore part includes a forecastle, needed to ensure a sufficient bow height for freeboard requirements.
In alternative, the ship may have increased sheer.
Figure 33 - Fore part - longitudinal section

The fore part includes anchoring and mooring equipments and the fore peak compartment, dedicated to ballast.
Special reinforcements of the bottom in the fore part (and just aft it) are provided to take into account slamming
pressures.
Special reinforcements also are provided on the side.
Special requirements for fore part are given in RINA Rules Part B, Chapter 9, Section 1.

4.1.3 Machinery space

The machinery space is dedicated to the propulsion engine, the electric generators, relevant auxiliaries and
systems, and a number of compartments
The double bottom in the engine room is specially arranged and reinforced to support the weight of the machinery,
and to hold the many tanks for lubricating oil, fuel oil, water and so on.
Special requirements for machinery space structure are given in RINA Rules Part B, Chapter 9, Section 3.

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Figure 44 - Machinery Space - longitudinal section

4.1.4 Aft part

The aft peak bulkhead, the upper deck and the outer shell delimit the aft part.
Its structure is quite complex due to the presence of the propeller or propellers, rudder and relevant machinery.
The connection between the peak structure and the rudder horn is to be specially designed both for structural
continuity and accessibility for inspection.
The aft part of the ship contains the aft peak compartment (or compartments) usually dedicated to water ballast.
Figure 55 - Aft part - longitudinal section

Special requirements for aft part structure are given in RINA Rules Part B, Chapter 9, Section 2.

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4.1.5 Superstructure

Superstructure is usually located in way of and above the engine room.
The length of a superstructure influences its participation to the global strength of the ship (in passenger ships in
particular the superstructure will collaborate with the hull in the ship’s longitudinal strength, i.e. in the stress
distribution).

Therefore the ends of superstructures are to be efficiently supported and connected to the underlying ship
structure.
Figure 66 - Superstructure

Requirements for superstructures are given in RINA Rules Part B, Chapter 9, Section 4.

4.1.6 Exceptions

There are many exceptions, of course, to the above-mentioned arrangement.
Passenger ships do not have an actual “cargo area” (the “cargo” are the passengers, in fact). The superstructures are
covering almost all the ship’s length.
Ro-ro and Ro-ro Passenger vessels have a garage that can run through the main part of the cargo area length.
Container ships have a part of cargo area aft of the engine room. Sometimes, this part can be very long.
Figure 77 - Emma Maersk - long cargo area aft of engine room1

1
Public domain photo taken from Wikimedia.

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Section 5:
SHIP STRUCTURE

5.1 MAIN STRUCTURAL BOUNDARIES OF THE SHIP

In this sub-section we will examine the “boundaries” or larges surfaces of the ship, both external and internal.
If we consider a transversal section and a longitudinal section of a ship we can have a look to the main boundaries:
Figure 88 - Boundaries

5.1.1 External boundaries

• Bottom
• Side
• Upper Deck
• Superstructure bulkheads
• (Bottom and side together with aft and fore surfaces form the shell)

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Section 5:
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5.1.2 Internal subdivisions

There are many exceptions, of course, to the above-mentioned arrangement.
• Inner bottom
• Decks
• Longitudinal bulkheads
• Transversal bulkheads

5.1.3 Decks

Decks have different purposes:

• Structural: contribute to longitudinal strength of the ship (especially the upper deck).
• Stability: (main deck) creating the main barrier to water ingress into the ship from the top.
• Functional: giving horizontal surfaces for cargo loading, passengers, equipment.

5.1.4 Side and bottom

Obviously side and bottom constitute the contact of the ship with the sea.

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Figure 99 - side and bottom

5.1.5 Inner bottom

The inner bottom is the surface constituting the top of the double bottom (sometimes defined as “Tank top”). Very
few ships are still constructed without the inner bottom. It was the case in the past for Oil Tankers, which now are
to be built with double hull for pollution prevention purposes.
Figure 1010 - Inner bottom

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Section 5:
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Its main purposes are:

• Structural: give more rigidity to the lower part of the ship and contribute to longitudinal strength.
• Functional: surface for cargo loading and boundary for the double bottom compartments,
• Safety and pollution prevention: reducing probability of water ingress in the cargo spaces and reducing
probability of oil spill from tanks.

5.1.6 Inner side

Its purposes are similar to those of the double bottom, (apart from cargo loading surface):
• Its purposes are similar to those of the double bottom, (apart from cargo loading surface):
• Structural: give more rigidity to the side, contributing to longitudinal strength
• Functional: to obtain side compartments for fuel or ballast; to give a flat surface for better cargo containment
(container ships, in some cases bulk; chemical)
• Safety and pollution prevention: reducing probability of water ingress in the holds and reducing probability of oil
spill from tanks.
Figure 1111 - Inner side

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5.1.7 Longitudinal Bulkheads

The main purpose of longitudinal bulkheads is the separation of the cargo space in different areas (generally tanks
on oil tankers and chemical tankers).
They also contribute to longitudinal strength2 and have an important role in absorbing the shear stresses.

Figure 1212 - Longitudinal Bulkhead

5.1.8 Transversal Bulkheads

The transversal bulkheads have different purposes:
• Structural: increase the structural rigidity of the ship
• Functional: subdividing the ship in different cargo or functional (e.g. machinery) spaces.
• Safety: create watertight compartments; contribute to fire protection by creating isolated spaces .
The number of transversal bulkheads depends on the requirements for cargo and for regulations on subdivision.
RINA Rules suggest a number of bulkheads depending on the ships length (See. Part B Chapter 2 Section 1).

2
Vertically corrugated longitudinal bulkheads to not contribute to longitudinal strength

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Figure 1313 - Transversal Bulkheads

Special cases of transversal bulkheads are:

• collision bulkhead
• aft peak bulkhead
• bulkhead (or bulkheads) forming the boundary of the engine room
• bulkhead (or bulkheads) forming the boundary of the generator room for ships with an electrical propulsion
plant,
“Transverse watertight bulkheads other than the collision bulkhead and the after peak bulkhead are to extend
watertight up to the freeboard deck.”
The distance of the collision bulkhead from the bow is prescribed by Load Line Convention and the RINA Rules.

5.1.9 Particular structures for Bulk Carriers

Bulk carriers have particular structures for cargo containment:
• Longitudinally:
o Hopper tank sloping plating
o Topside tank sloping plating
• Transversally:
o Lower stool
o Upper stool
The hopper plating and the lower stool are meant to facilitate bulk cargo stowage and unloading.
Figure 1414 - Bulk Carrier transv. section with hopper and topside tanks

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Figure 1515 - - Bulk Carrier - longitudinal section with lower and upper tanks

The topside plating and the upper stool are meant to avoid having empty spaces in the upper corners of the holds
when full-loading the hold, for stability purposes.
The hopper and topside tanks also contribute to the torsion rigidity of the ship section and in part to the longitudinal
strength of the ship, while the lower and upper stool contribute to the rigidity of the transversal bulkheads, and also
to torsion rigidity (by strongly connecting the two sides of the ship).
The transversal bulkheads on bulk carriers are usually of the corrugated type to facilitate loading/unloading and
cleaning of the bulkhead surfaces.
Figure 1616 - Bulk Carrier cargo hold - nomenclature

5.1.10 Openings

Openings may be present in:
• decks (hatches for cargo loading/ unloading, ramps, elevators, manholes, small hatches for cargo stowage)

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• side (ramps, doors)

• bulkheads (doors)
• aft part of the ship (ramps for ro-ro ships))
• fore part of the ship (ramps)

They can be present also in watertight bulkheads (even if it is recommended to limit them to a minimum) subject to
certain conditions.
Figure 1717 - Hatch opening

Special kind of openings are those provided to give access to the different parts of the ship, e.g.
• Manholes on the inner bottom, floors, girders, decks, bulkheads…
• Hatchways to access tanks from the deck on oil tankers.
• Passageways in bulkheads

5.2 STRUCTURE COMPONENTS

In this Section we will examine the “elementary” parts of the ship, such as: plating. stiffeners, primary supporting
members, pillars, brackets

5.2.1. General

A steel ship has a structure consisting of panels of welded plating “strakes”), supported by stiffeners (or “secondary
members” - welded to the plating) which are supported by primary supporting members or other main structures.

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The secondary stiffeners on the shell and the decks can be longitudinally oriented (i.e. almost parallel to the
longitudinal axis of the ship) or transversally (i.e. contained in one ship section). The distance between these
stiffeners usually is between 600 mm and 1000 mm.
On a transversal bulkhead they can be vertical or horizontal.
The structural design of a ship is never solely transverse or solely longitudinal. The extent of transverse and
longitudinal structure depends on many factors.
The longitudinal framing on decks, shell, inner bottom and longitudinal bulkheads give higher structural efficiency
because the longitudinal stiffeners (“longitudinals” ) contribute to the ship section modulus and is also more efficient
in terms of construction procedures.
Figure 1818 - Drawing of a deck

The transversal stiffening is needed in bulk carrier to allow the cargo to be loaded and unloaded avoiding it to
accumulate on longitudinal structures. Transversal stiffening may be more practical for fore and aft sections and
superstructure bulkheads.

5.2.2 Plating

The deck and shell plating are the most important parts of a vessel’s structure since they form a watertight skin and
make up the principle longitudinal strength member of the hull girder. The plates are arranged in fore and aft lines
around the hull, called strakes, and for identification are lettered starting with the strake adjacent to the keel, this
strake being “A”. The separate plates in the strakes are numbered, usually from aft, thus plate “C 12 port” will be
th rd
the 12 plate from aft in the 3 strake up from the keel on the port side.
The thickness of the plating generally depends on the length of the vessel and frame spacing. The scantlings of all
continuous longitudinal members, based on the minimum section modulus as required for the midship section

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thickness, are to be maintained for 0.4 Lamidships and tapered gradually to a minimum end thickness at 0.1 L for
the deck.
The plating constituting the shell is made by welding previously cut and shaped plates next to one another, thereby
forming longitudinally arranged “strakes”.
Starting from the centreline at the bottom of the ship and working up to the deck, we have:
• keel plate;
• 1st strake of plating adjacent to the keel, known as the garboard;
• 2nd strake, called the counter-garboard;
• strakes of bottom plating (3rd, 4th, 5th etc bottom strake);
• bilge plate(s);
• 1st 2nd, 3rd etc side strake;
• second last side strake, i.e. the first strake below the sheerstrake;
• last side strake, called the sheerstrake;
• 1st 2nd, 3rd etc deck strake, from the ship’s centreline;
• last strake of deck plating welded or riveted to the sheerstrake, known as the stringer.

Figure 1919 - Drawing of shell expansion

The various strakes are welded to each other in accordance with a very specific welding sequence enabling the
plates to expand without causing dangerous stresses.
The different primary structures, which are internally welded to the plating, need to have “slots” in way of each weld
between the strakes of plating (see Figure 2020).
Figure 2020

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Section 5:
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It can be quite obvious that the thickness of the plating depends on the loads, and therefore depends also (but not
only) on the ship’s length.
On a ship’s shell, as the pressure increases from the top to the bottom, also the shell thickness generally
decreases from the bottom to the side. The thickness increases again in way of the sheerstrake-stringer
connection; high strength steel is often used for these zones. Conversely, the deck plating is almost uniform or
decreases very slightly from the side to the ship’s centreline.

5.2.3 Stiffeners

They are needed to support the plates to maintain their shape in order to keep plate stresses within reasonable
values as shown in the picture.

Moreover, longitudinal stiffeners contribute to the stiffness of the ship as a whole.

Examples of stiffeners
• Deck Beams
• Deck Longitudinals, Side Longitudinals
• Bulkhead Stiffeners
Stiffeners are usually made by standard profiles (bulbs, angles, flat) or built-up section (especially on large ships).
For longitudinal stiffeners continuity is essential in order to let stresses flow along the ship’s structure, therefore
they are continued through bulkheads, floors, girders (welded to them only on part of the perimeter, with possible
fitting of a collar plate to improve shear transmission).
Figure 2121 - welding of stiffener to PSM without and with collar plate

In case the bulkhead is to be watertight, a watertight collar is to be welded around the longitudinal.
The connection of stiffeners to PSM is often improved by using brackets.

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Figure 2222 - connection between stiffener and PSM

Figure 2323 - Bracket

Figure 2424 - stiffeners typical sections

5.2.4 Primary supporting members

They are needed to maintain the shape of the hull girder on the local level, or in other words to support the ordinary
stiffeners.
There can be two orders of PSM, one orthogonal to the other. Typical example is the double bottom structure with
floors and girders, or a ro-ro deck.
PSM can be built-up section (T or L) or diaphragms made by stiffened plating, e.g. inside double bottom (floors
and girders) or double side, or cofferdam.

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Figure 2525 - examples of PSM

5.2.5 Pillars

The primary function of pillars and girders is to transmit the deck loads to the bottom structure, where the distributed
loads are supported by the upthrust of the water pressure. They also tie the vessel together vertically, thus
preventing the flexing of the decks in response to the bending of the side frames under varying water pressures
and vertical accelerations in heavy weather. Normally a pillar will be in compression, though in certain cases it may
be subjected to tension and even side loads, resulting from the movement of the cargo when rolling.
.Figure 2626 - Square section pillar

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Pillars should be fitted in the same vertical line whenever possible. Effective arrangements should be
made to distribute the load at the head and heel, which should be over the intersection of a plate floor and
side girder without manholes below the pillar. Where pillars are not arranged directly above the
intersection of floors and girders, then partial floors and intercostals should be fitted.
Figure 2727 - Ciruclar section pillars on a cruise vessel3

In lieu of pillars, a non-watertight pillar bulkhead may be fitted on the centre line. This usually extends from the
transverse bulkhead to the hatch coaming. Such an arrangement facilitates the fitting of shifting boards when
carrying grain cargoes

5.2.6 Corrugated Bulkheads

A particular kind of stiffening arrangement is the corrugated bulkhead.

3
Courtesy of Jim G (http://www.flickr.com/people/jimg944/) License http://creativecommons.org/licenses/by/2.0/deed.en

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The corrugated bulkhead is made by plating, which is bent in order to obtain corrugations. The corrugation itself
replaces the ordinary stiffening.
One main advantage of corrugated bulkhead is to facilitate loading and unloading (with vertical corrugations) in
bulk carriers, and to facilitate cleaning in chemical tankers.
The corrugations are therefore usually vertical, however they can also be horizontal, for instance in longitudinal
bulkheads in order to allow contribution of the plating to longitudinal strength.
Figure 2828 - Drawing of a corrugated bulkhead

Crossing of a transversal and longitudinal bulkhead is better obtained if both have vertical corrugations; other ways
(transversal with vertical corrugations and longitudinal with horizontal corrugations or vice-versa, but also both
bulkheads with horizontal corrugations) should be avoided. Anyway the intersection between horizontal and vertical
corrugations, and between horizontal corrugations is to be carefully inspected because it can induce stress
concentrations.

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