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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
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
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
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 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 ?