Section 3 Deep Tank Construction

301. Bulkhead plating

The thickness of bulkhead plating is not to be less than that obtained from the following formula.

ĖĦÈĬJY ĞËĦÈ (mm)

Å : spacing of stiffeners (m )

h : distance given belows, whichever is the greater (m )

(1) Vertical distance from the lower edge of bulkhead plating to the midpoint of the distance between the top of tank and the top of overflow pipe. However, additional hydraulic pressure is to be considered for the bulkheads of large tanks.

(2) 0.7 times the vertical distance measured from the lower edge of bulkhead plating to the point of 2.0 m above the top of overflow pipes (m )

302. Stiffeners

The section modulus of stiffeners is not to be less than that obtained from the following formula.

ĒÆÅYŶË (cmĖ )

Å and Ŷ : as specified in 203.

Y : vertical distance given belows (m ), whichever is the greater, measured from the midpoint of Ŷ for vertical stiffeners, or from the midpoint of distance between the adjacent stiffeners for horizontal stiffeners.

(1) from the lower edge of bulkhead plating to the midpoint of the distance between the top of tank and the top of the overflow pipe. However, additional hydraulic pressure is to be considered for the bulkheads of large tanks.

(2) 0.7 times the vertical distance measured from the lower edge of bulkhead plating to the point of 2.0 m above the top of overflow pipes (m )

Æ : Coefficient given in Table 7.2, according to the type of end connection of girders supporting

stiffeners.

Ch 7

Table 7.2 Value of Æ

303. Girders supporting stiffeners

1. The section modulus of girders supporting stiffeners is not to be less than that obtained from the following formula.

ĒĦËĖÅYŶË (cm Ė)

Å : breadth of the area supported by girder (m )

Y : vertical distance (m ) measured from the midpoint of Å for horizontal girders, and from the midpoint of Ŷ for vertical girders, to the top of Y specified in 203.

Ŷ : span measured between adjacent supports of girders (m )

2. The moment of inertia of girder is not to be less than that obtained from the following formula.

However, the depth of girder is not to be less than 2.5 times of the depth of slots of stiffeners.

ĖŊYŶĖ (cm Ė)

3. The thickness of girder plating is not to be less than that obtained from the following formula.

10 ÅË + 2.5 (mm )

ÅË : spacing of web stiffener or depth of girder, whichever is the smaller (m )

304. Top and bottom construction

The scantling of structural members forming the top or the bottom of deep tanks is to be in ac- cordance with the requirements in Sec 3, regarding those as the members the deep tank bulkheads at the same location. However, the scantling is not to be less than that required for deck platings, and for the top platings of deep tanks, the thickness is to be at least 1 mm greater than that ob-

tained from the formula of 301.

305. Plating of bulkhead and girder not in contact with sea water

The thickness of bulkhead and girders which are not in contact with sea water in voyage condition may be reduced from the requirements specified in 301. and 303. 3 by value given as follows. However, bulkhead platings in way of the location such as bilge well, etc. are to be regarded as platings in contact with sea water.

For plating of which one side is in contact with sea water For plating of which neither side is in contact with sea water

: 0.5 mm

: 1.0 mm