Section 2 Construction of Watertight Bulkheads

201. Thickness

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

ĖĦË Å ĬJY Ğ ËĦÈ (mm )

Å : spacing of stiffeners (m )

h : distance from the lower edge of bulkhead plate to upper deck at ship centerline (m ).

However, h is not to be less than 3.4 m .

202. Increasement of thickness

1. The thickness of lower strake plating of bulkhead is not to be less than that obtained from the for- mula given in 201. plus 1 mm .

2. The lowest strake of bulkhead plating is to extend at least 600 mm above the top of inner bottom plating in way of double bottom construction or at least 900 mm above the keel plate in way of single bottom construction. Where the double bottom is provided only on one side of bulkhead, the

extension of the lowest strake is to be of the greater value between two cases above mentioned.

3. The thickness of bulkhead platings in way of bilge wells is to be at least 2.5 mm thicker than that given in 201.

4. The thickness of deck plating in way of bulkhead recesses is to be at least 1 mm greater than that given by 201., regarding the deck plating as bulkhead plating with same height and the beams as the stiffeners with same spacing. However, the thickness is not to be less than that of deck plat-

ing in that location.

203. Stiffeners

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

Ch 7

ËĦĒÆÅYŶË (cm Ė)

Ŷ : span

measured between the adjacent supports of stiffeners including the length of connection

(m ). However, where girders are provided, it is the distance from the heel of end connection to the first girder or the distance between the girders.

Å : spacing of stiffeners (m )

Y : vertical distance measured from the midpoint of point of distance between the adjacent stiffeners at the center line of ship (m ). However, where

Ŷ for vertical stiffeners, and from the mid- for horizontal, to the top of bulkhead deck

the vertical distance is less than 6.0 m , Y is

to be taken as 0.8 times the vertical distance plus 1.2 m .

Æ : value given in Table 7.1 (m )

Table 7.1 Value of Æ

204. Girders

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

ĖĦĒÈÅYŶË (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 respectively.

Ŷ for vertical girders, to the top of bulkhead deck at the center line of ship

However, where the vertical distance is less than 6.0 m , Y is to be taken as

0.8 times the vertical distance plus 1.2 m .

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

2. The moment of inertia of girders 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.

ËŊYŶĖ (cm Ė)

Y and Ŷ

: specified in Par 1

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

10 ÅË + 1.5 (mm)

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

Ch 7

4. The girder is to be provided with tripping brackets at an interval of about 3 m and the tripping brackets are to be so arranged to support the face plating of girders.

205. Platings of collision bulkhead

The thickness of plates and section modulus of stiffeners for collision bulkhead are not to be less than those specified in the formula of 201. and 203. respectively taking Y as 1.25 times the speci- fied height.