Deck plating is the process of covering deck beams which helps to counter act the bending moments experienced  at the deck and bottom of ship.

Shell and Deck Plating

The ship for the purpose of stresses may be assumed to be a box girder with the deck and bottom plating as the upper and lower sides of the girder and the side plating, the sides of the girder, this girder provides the main strength to the ships, however it would be sufficient to support the ship alone. it must therefore be adequately strengthened to counter act the bending moments which the deck and bottom suffer and the sharing forces which the side plating suffers.

Why Deck Plating

The main deck of the ship must be able to maintain the weather tightness. Large openings in the decks are cut to provide suitable hatchways to work cargo on general cargo and bulk carriers. Due to these large openings, the deck is substantially weekened, and measures have to be taken to strengthen the ships in the vicinity of these openings. On general cargo ships, it is usual to carry deck cargo. This also demands additional strengthening of the decks.

The decks are cambered from side to side and a slight sheer in the longitudinal direction to:

1. Reduce the amount of shipped seas.
2. Accelerate the drainage of shipped seas.

The line of deck plating connecting to sheer strake is called the Deck Stringer. Many modern ships especially large vessels have rounded sheer strakes as this provides additional longitudinal strength.

Side and Bottom Plating

The shell plating consists of the side and bottom plating. This part of the ship’s structure is arranged in fore and aft lines of plating called strakes. Strakes vary in size. The welded joints connecting one strake to another are called seams. These run along the longer edge of the plates (horizontally). The lines joining the plates in a particular strake are called butts and run vertically on the sides and horizontally on the bottom. The strake on each side of the keel is called the Garboard strake. The uppermost strakes which join up with the deck plating are called the Sheer Strakes.

The width of the ship is much more in the mid ships portion than at the ends. This change in dimensions calls for adjustment in the number of strakes as it would be impossible to have the same number of strakes amidships at the ends. In practice, this problem is overcome by reducing the width of the strakes to a certain extent and merging two strakes into one towards the ends. The first plate of the newly formed strakes is called a Stealer Plate.

Scantling of plates vary with position .generally, the scantlings are increased from top to bottom. This is because the bottom plating has to be able to withstand the longitudinal bending moments, water pressure, heavy weather stresses and loading distributions etc.

The plating in the pounding region, sheer strakes, deck stringers, garboard strakes and keel plate are generally thicker than the rest of the plating.