06 - DNVs Hull Str for WW - Hull Str - Cargo Area - Side

8/2/2019 06 - DNVs Hull Str for WW - Hull Str - Cargo Area - Side

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DNVs

Hull Structure course for

World Wide Shipping

6 - Hull Structure cargo area

Side


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16.03.2004Slide 2

1. SideHull Structural Breakdown -

Ship side

Side

Bottom

Deck

Transverse bulkhead

Longitudinal bulkheadWeb frames

1.

2.

3.

4.

5.

6.


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16.03.2004Slide 3

1. SideStructural build up of ship side

single skin tanker

Cross ties

Transverse

bulkhead

Side plating withlongitudinals

StringersWeb frame


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16.03.2004Slide 4

1. SideStructural build-up of a ship side

- double hull tanker

Side plating with

longitudinals

Stringers

Web frame

Inner side platingwith longitudinals


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16.03.2004Slide 5

1. SideStructural functions of ship side

Watertight integrity

- Take up external sea loads and transfer these into thehull girder

- Resist internal pressure from cargo and ballast

Web in hull girder

- Side plating act as the web in the hull girder beam


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16.03.2004Slide 6

1. SideLoads on the ship side - example

Full centre tank

Fully loaded

condition

Net force

Water

Line

Ballast condition

Full wing tank

Net force

Water

Line


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16.03.2004Slide 7

1. SideLocal function: Watertight integrity

-Side longs are supported at the web frames

- Web frames are supported at the cross ties

and at the deck and bottom

Part of web frame supported

at two cross ties, shear max

towards supports


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16.03.2004Slide 8

1. SideDouble hull ship side

The structural functions of a double hull ship side is the same as for a

single hull:

As there are no cross ties,

side web frame is supported

at the deck and bottom

High shear stress


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16.03.2004Slide 9

1. SideGlobal function: Web in hull girder

Global shear forces resulting from uneven distribution of cargo and

buoyancy are taken up in the ship side plating

Buoyancy W

eights

Shear stress distribution resulting fromglobal loads for midship section


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16.03.2004Slide 10

1. SideStringers in a double side

Stringers contribute to the stiffness of the double hull ship side,

which means:

High shear stress instringer towards the

transverse bulkhead

- Less relative deflection

for side longitudinals at thetransverse bulkheads


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16.03.2004Slide 11

1. SideCharacteristic damages for ship side:

1. Cracks in side longitudinals at web frames2. Cracks in side longitudinals at transverse bulkheads

3. Cracks in web frame cut-outs for longitudinals

4. Indents of side shell and stiffeners


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16.03.2004Slide 12

1. SideCrack in side longitudinals

Crack in side longitudinal

tripping bracket connection toweb frame (various wing tanks)

Side longitudinal flatbar

connection to web frame


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16.03.2004Slide 13

1. SideCause for cracking in side longitudinals

Dynamic loads (sea

and cargo) are forcingthe side longitudinal to

flex in and out

High alternating bending stresses towards the endsupports (web frames)

Highly stressed areas created around geometric

hard points (bracket toes, scallops, flat bars)


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16.03.2004Slide 15





C k i id l i di l


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16.03.2004Slide 16

1. SideCrack in side longitudinal at

transverse bulkhead

Side longitudinal connections

to transverse bulkheads

Cracks in side longitudinal connection to

stringers at transverse bulkhead


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16.03.2004Slide 17

1. SideWhy cracking at transverse bhd.?

Sea

pressure

Relative deflections occur betweenthe rigid transverse bulkhead and

the flexible web frame construction

Ship side

The relative deflection induces additional

bending stresses at the end connection of

side longitudinals to the transverse bulkhead


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16.03.2004Slide 19






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16.03.2004Slide 20

1. SideCracks in web frame cut outs

Cracks around openings for

side longitudinals in web

framesCracks

Cause for cracking in cut outs


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16.03.2004Slide 21

1. SideCause for cracking in cut outs

for longitudinals

Sea loads induce shear stresses in the web frame

Shear stress

Shear stress

High shear stresses

around openings etc,

where shear area is

reduced


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16.03.2004Slide 22

1. SideConsequence of damage

Cracks in side longitudinals:- oil leakage and pollution

- longitudinal may break off

- in worst case (a series of cracks in samearea) could induce a larger fracture (loss

of ship side)

Cracks in cut outs for longitudinals:

- loss of structural strength for the web frame (webframe cracked through)

- may lead to collapse of surrounding structure

Suggestions?

Suggestions?


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16.03.2004Slide 24

1. SideIndents of side shell with stiffeners

The terms indents and buckling should not be mixed up with each

other, as the cause for these damages are different:

-Indents: Mainly due to contact damages

-Buckling: Due to excessive in-plane stresses

Mainly from contact damages:


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16.03.2004Slide 25

1. SideConsequense of indents

Sharp indents may lead to

cracks and possible leakage


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16.03.2004Slide 26

1. SideConsequense of indents

Large area set in (plating and stiffeners)

gives reduced buckling capacity

Adjacent areas may then be overloaded


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16.03.2004Slide 27

1. Side

Questions ?

06 - DNVs Hull Str for WW - Hull Str - Cargo Area - Side

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