Section 1 Shell Plating

Ch 4

101. General

1. Consideration for corrosion

The thickness of shell plating, at such places where excessive corrosion is anticipated due to the location, is to be increased over that required by requirements of this Chapter.

2. Special consideration for contact

In case where there is possibility of damage on the shell plating due to the working condition of the dredger, special consideration is to be given to the thickness of shell plating.

102. Plate keels

1. Scantling of plate keels

(1) The breadth of the plate keel over the tained from the following formula.

whole length of the ship is not to be less than that ob-

Ä ≧ 90 m : 2 Ä + 1,000 (mm ), Ä < 90 m : 4.5 Ä + 775 (mm )

(2) The thickness of plate keels over the whole length of the ship is not to be less than the thick- ness of bottom shell plating obtained from the requirement in the 103. 4 increased by 1.5 mm . However, this thickness is not to be less than that of the adjacent bottom shell plating.

103. Shell plating at midship part

1. Minimum thickness

The thickness of shell plating below the upper deck at midship part is not to be less than that ob- tained from the following formula;

0.044 Ä + 4.6 (mm )

2. Thickness of side shell plating

(1) The thickness of side shell plating other than sheer strake is not to be less than that obtained from the following formula.

ĖĦËÅĬJẀĞŊĦŊĖÄ ĞËĦÈ (mm)

Å : spacing of longitudinal or transverse frames (m )

(2) In case of the square bilge shape dredger, the thickness of the shell plating at the lowest part is not to be less than that obtained from the requirements in above (1) or 103. 4 whichever is the greater.

3. Thickness of sheer strake

The thickness of sheer strake is not to be less than 75% of the thickness of the stringer plate. However, the thickness is not to be less than that of the adjacent side shell plating.

4. Thickness of bottom shell plating

The thickness of bottom shell plating is to be obtained from one of the followings;

Ch 4

(1) In a transverse framing system, the thickness is not to be less than that obtained from the fol- lowing formula;

ĖĦĒÅĬJẀ Ğ ŊĦŊĖÈÄ Ğ ËĦÈ (mm )

Å : spacing of transverse frame (m )

(2) In a longitudinal framing system, the thickness is not to be less than that obtained from the following formula;

ĖĦŊÅĬJẀĞŊĦŊĖÈÄ ĞËĦÈ (mm )

Å : spacing of longitudinal frame (m )

104. Shell plating for fore and aft end parts

1. Shell plating for fore and aft end parts

The thickness of shell plating may be gradually reduced from the midship section toward the fore

and aft end parts. However, the thickness of the fore and aft parts within 0.1 Ä is not to than that obtained from the following formula.

be less

0.044 Ä + 4.6 (mm )

2. Shell plating of bottom strengthened forward

The thickness of shell plating of bottom strengthened forward is to be in accordance with ings;

(1) Where the fore draft in ballast loaded condition is not more than 0.025 Ä , it is not to than that obtained from the following formula.

follow- be less

ËĦËÈÅĬJÄ Ğ ËĦÈ (mm )

Å : Spacing between frames, and girder or longitudinal shell stiffeners, whichever is the smaller. (m )

(2) Where the fore draft in ballast loaded condition is not less than 0.037 Ä , it may be the same

as that obtained from the 104. 1

(3) The smallest fore draft in the ballast loaded condition is in between the above two, the thick- ness is not to be less than that as obtained from interpolation.

105. Side plating in way of superstructure

1. Side wall plating in way of superstructure

The side wall plating in way of superstructure is not to be less than that obtained from the follow- ing formula. However, it is not to be less than 5.5 m .

Within 0.25 Ä from the fore end : ËĦËÈÅĬJÄ Ğ ËĦŊ (mm )

Others

: ŊĦŊĖÅĬJÄ Ğ ËĦŊ (mm )

Å : Spacings between longitudinal or transverse frames at that place. (m )

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106. Local compensation of shell plating

1. Shell plating fitted with hawse pipe and plating below

The shell plating fitted with hawse pipes and plating below is to be increased in thickness, or to be doubled, and of appropriate structure so that its end may not be damaged by the anchor or cables.

2. Shell plating of transverse framing system

In ships with transverse framing system, sufficient consideration is to be given to the prevention of

buckling of the shell plating. For the bottom shells within 0.4 Ä of the midship, the stiffeners with proper scantling are to be arranged with the spacing of not more than 2 times the spacing of the frames in that part. However, due consideration may be given where Ä is less than 60 m .