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Strengthening of ship structure We can conclude from previous discussion, that a ship has to overcome with many stresses all together to be structurally strengthened.
For that framing system is adopted,
Transverse Framing system
Longitudinal Framing System
Combined framing system<br>
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Transverse Framing System This type of framing system is generally adapted in small vessels and ships
which are basically operating in calm waters
Since wave bending of ship is not happening in such ships
transverse strengthening will be more efficient.
Longitudinal deck girders support the transverse deck beams
Longitudinal strength in a transversely framed ship is provided by :
The centre girder, the shell plating and inner bottom plating
By a number of large, widely spaced longitudinal members e.g.
longitudinal deck girders.<br>
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Transverse Framing system Disadvantages
Vertical support for decks requires more closely spaced transverse bulkheads(hence smaller compartments) or
Pillars (stanchions) or
Longitudinal Bulkheads
Advantages
Open, nearly rectangular interior space
Ideal for stowing large, irregular, break-bulk items or Vehicle(RO-RO)<br>
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Transverse
Side Longitudinal girders
Centre girders
Deck longitudinals<br>
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Longitudinal Framing System All the ship’s secondary supporting members are fitted the longitudinal direction and are known as longitudinals.
Side shell longitudinal are called as stringers
The system consists of many small, closely spaced longitudinals supporting the plating directly and being supported in turn by a few largely spaced transverses.
They also contribute to the longitudinal strength of the ship, making the longitudinal framing system more structurally efficient than the transverse system.<br>
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Stringers
Bulkheads<br>
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Longitudinal Framing system Disadvantages
No large, open interior spaces
Difficult to load or unload break-bulk items
Difficult to stow large, irregular shaped items.
Advantages
Widely spaced transverse bulkheads allow for large (i.e. long ) continous cargo spaces (“tanks”)
Ideal for stowing liquids (reduced free surface effects)<br>
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Beams & Beam Knees(stiffener brackets) Beam is a strength member to give strength to the ship plating or deck in the transverse direction
Beam knees are the junction at which the frames connect the beams
Typically an “I” section.
Brackets gives connection to the longitudinals and<br>
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Water tight Bulkheads A watertight bulkhead is a transverse bulkhead mounted on the tank top and it must extend right to the uppermost continuous deck.
Watertight bulkheads are installed to:
Divide the ship into watertight compartments and thereby limit flooding if the hull plating is damaged;
Improve the transverse strength of the structure;
Prevent distortion of the hull plating;
Support the deck girders and longitudinal;
Rigidly attach the tank top to the upper deck;
Greatly slow the spread of fire.<br>
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Water tight Bulkheads Transvers Bulkhead
Corrugations can be vertical or horizontal.
Longitudinal bulkhead –must be horizontal
Corrugations.
Lighter scantlings are installed around
Machinery space since they do not
Contribute to strength of ship<br>
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Forward section of ship including bulkhead<br>
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SHELL EXPANSION AND NUMBERING OF PLATE<br>
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SHELL EXPANSION AND NUMBERING OF PLATE Shell expansion plan : can also be done
Lettering from keel strake and up
Numbering from aft to forward
Outermost strakes on deck<br>
