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Ship Construction

Hull Structure

 

Structural components on ships’ plans and drawings: frames, floors, transverse frames, deck beams, knees, brackets, shell plating, decks, tank top, stringers, bulkheads and stiffeners, pillars, hatch girders and beams, coamings, bulwarks

 

 

 

Bow and stern framing, cant beams, breasthooks

 

Description of standard steel sections: flat plate, offset bulb plate, equal angle, unequal angle, channel, and tee

 

Longitudinal, transverse and combined systems of framing on transverse sections of the ships

Longitudinal framing – Open floors

Longitudinal framing – Plate floors

Transverse framing – Open floors

 

Transverse framing – Plate floors

Duct keel

 

 

Stress concentration in the deck round hatch openings

Holes cut in the deck plating by way of hatchways, masts and others create areas of high local stress due to lack of continuity created by the opening.

Compensation for loss of strength at hatch openings

Compensation around some of these openings may be overcome by increasing the sizes of the material used, buy a careful disposition of the material and by paying careful attention to the structural design.

Compensating for the stress concentration around hatch corners by rounding off the square hatch corner ends

 

 

The corners radiused to reduce the stress concentration

A hatch corner in plan view, showing the structural arrangements

A transverse section through a hatch coaming, showing the arrangement of coamings and deep webs

 

 

Deck‑freeing arrangements - scuppers, freeing ports, and open rails

 

Connection of superstructures to the hull at the ship’s side

A plane bulkhead, showing connections to deck, sides and double bottom and the arrangement of stiffeners

 

A corrugated bulkhead

Transverse bulkheads have vertical corrugations and fore and aft bulkheads have horizontal ones

The basic idea of a bulkhead in addition to the water tight integrity is to add to the girder strength of the ship beam.

Thus for a transverse bulkhead, which extends from the port to the starboard side or vice versa, the framing is done in a vertical manner so that the compressive and the tensile stress may be reduced for the beam.

Similarly for a longitudinal bulkhead which runs parallel to the shipside the framing is done vertically, again so that the additional strength would enhance the stress compensating effect of the ship beam.

Construction of the corrugated bulkhead

A fitted corrugated bulkhead

 

Purpose of bilge keels and their attachment to the ship’s side

Bilge keels are fitted at the turn of the bilge to resist rolling. They also improve the steering qualities of the ship – though very slightly.

The ends are to be gradually tapered and should not end on an un-stiffened panel.

 

Stress relieving while fitting the bilge keel

Hold drainage systems

The hold drainage system of older cargo vessels had limber board covered upper side of the tank side bracket areas. The drainage conduit was these areas and the pipelines were connected to the after ends, which passed through the lightening holes in the DB’s.

 

The limber boards were removable for cleaning as they were frequently damaged (edges) leaving gaps through which cargo residue would accumulate.

Modern ships do not have the side bilges and have only a strum box at the after end of the holds and these are connected in the similar way to pipelines, which run through the DB’s.