Section 2 Bulkheads of Deep Tanks

201. Bulkhead plates

The thickness of deep tank bulkhead plating is not to be less than obtained from the following for- mula:

ᾼ Ņ ĮǾĴ ĊΡ̓Üᾜ Ñ ĪǾJ (mm)

where:

Ċ = Spacing of stiffeners (m)

h =

Distance given below, whichever is the greater:

(1) Vertical distance measured from the lower edge of plate to the midpoint of the distance be- tween the top of tanks and the top of overflow pipes (m). For bulkheads of large tanks, ad- ditional water pressure is to be considered.

(2) 0.7 times the vertical distance measured from the lower edge of plate to the point of 2.0 m

above the top of overflow pipes (m)

202. Bulkhead stiffeners

The section modulus of bulkhead stiffeners is not to be less than obtained from the following for- mula:

Ě Ņ Ǽ ĊᾜᾨĪ (cm3)

where :

Ċ, l

= As specified in Ch 14, 203.

h = Vertical distance given below, whichever is the greater, the lower end being regarded as the

mid-point of l

for vertical stiffeners and as the mid-point of distance between the adjacent stiff-

eners for horizontal stiffeners.

(1) Vertical distance measured from the lower end to the mid-point of the distance between the top of tanks and the top of overflow pipes (m). For bulkhead stiffeners of large tanks, addi- tional water pressure is to be considered.

(2) 0.7 times the vertical distance measured from the 1ower end to the point of 2.0 m above the top of overflow pipes (m).

Ǽ = Coefficient given in Table 15.1 according to the type of end connections.

Table 15.1 Value of Ǽ

203. Girders supporting bulkhead stiffeners

1. The section modules of girders supporting bulkhead stiffeners (here in after referred is not to be less than obtained from the following formula:

to as "girder")

Ě Ņ KǾÌĮ ĊᾜᾨĪ (cm3)

where :

Ċ = Breadth of the area supported by the girders (m)

h = Vertical distance measured from the mid-point of Ċ for horizontal girders, and from the

midpoint of l

for vertical girders, to the top of h specified in 202. (m)

l = Span between the supports of girders (m)

2. The moment of inertia of girders is not to be less than obtained from the following formula. In no case is the depth of girders to be less than 2.5 times the depth of slots for stiffeners.

Ā Ņ ĮL ᾜᾨĨ (cm4) where :

h, l = As specified in Par 1.

3. The thickness of web plates is not to be less than obtained from the following formula:

ᾼ Ņ LǾLÌ ĊÌ Ñ ĪǾJ (mm)

where:

ĊÌ = Spacing of web stiffeners or the depth of girders, whichever is the smaller (mm)

204. Top and bottom construction

The scantlings of the members forming the top or the bottom of deep tanks are to be in accord- ance with the requirements in this chapter, regarding the members as the members forming the deep tank bulkheads at the location. In no case are they to be less than required for the deck plat- ing or the bottom plating at the location. For top plating of deep tanks, the thickness of plates is to be at least 1 mm greater than the thickness specified in 201.

205. Scantlings of members not in contact with sea water

The thickness of plates of bulkheads and girders which are not in contact with sea water in service conditions may be reduced from the requirements in 201. and 203. by the values given following. However, bulkhead plates in way of the location such as bilge wells are not to be regarded as the plates in contact with sea water.

For the plates of which only one side is in contact with sea water : 0.5 mm For the plates of which neither side is in contact with sea water : 1.0 mm