Topic - 19 Ballast and Deep Tank Bulkheads

1.                  Plating

Plating of Ballast and Deep tank bulkheads is to be of thickness obtained from the following equation:

t = [sk√qh/254] + 2.5 mm           t = [sk√qh/460] + 0.10 in. (3-2-7/3.1)

                     =  mm

But not less than 6.5 mm (0.25 in.) or s/150 + 2.5 mm (s/150 + 0.10 in.), whichever is greater,

In addition to the above, the top strake of effective longitudinal bulkheads is not to be less in thickness than given by the following

t = 0.0521L + 4.8 mm            t = 0.000625L + 0.19 in.

                              = mm

Finalized ballast and deep tank bulkhead thickness = 8 mm

And the second top strake is not to be less in thickness than given by the following:

t = 0.0347L + 5.3 mm             t = 0.000417L + 0.21 in.

                             = mm

Finalized ballast and ballast tank bulkhead thickness =  mm

2.                   Stiffeners

Bulkhead stiffeners are to have their ends attached. Each stiffener, in association with the plating to which it is attached, is to have a section modulus SM not less than that obtained from the following equation:

SM = 7.8chsl²Q cm³                   SM = 0.0041chsl²Q in³      (3-2-7/3.3)

For horizontal or vertical stiffeners on transverse bulkheads and vertical stiffeners on longitudinal bulkheads, SM=cm³

     Depth considered = in.

     Web thickness = in.

     Flange thickness = in.

     Flange width =  in.

                                         SM_obtained =  cm³

3.                   Stringers and Webs

Ø    Strength Requirements

Stringers and webs which support bulkhead stiffeners are to have section moduli SM as obtained from the following equation. Where the expanse of the bulkhead is relatively large, consideration is to be given to fitting of deep girders in line with webs and stringers so as to obtain complete planes of stiffness.

                         SM = 4.74chsl²Q cm³             SM = 0.0025chsl²Q in³          (3-2-7/3.5.1)

                               =  cm³

     Depth considered =  in.

     Web thickness =  in.

     Flange thickness =  in.

     Flange width =  in.

                                         SM_obtained =  cm³

Ø    Proportions

The stringers and webs are to have a depth of 125 mm per meter (1.5 in. per foot) of unsupported length and the thickness is to be not less than 1 mm per 100 mm (0.01 in. per inch) of depth plus 3 mm (0.12 in.). See also 3-2-4/3.11. In general, the depth of the girder is to be not less than 2.5 times the depth of the cutouts. See also 3-2-4/3.9iv).

Stringers and webs are to have a depth =  mm

Thickness is to be not less than =  mm

Finalized thickness =  mm

Finalized Depth =  mm