Topic - 15 Hull structures and arrangement (PART-I)

     Longitudinal Strength

Longitudinal Hull Girder Strength

Ø  Strength Standard

The required hull girder section modulus SMR amidships, to the deck and bottom is to be obtained from the following equation:

SM_R = K SM_b cm²-m   (in²-ft)           

                                         = X cm²-m

Ø  Hull Girder Moment of Inertia

The hull girder moment of inertia I amidships is to be not less than obtained from the following equation:

I = 0.03SM_RL cm²-m² (in²-ft²)         

                                           = X cm²-m²

        Shell Plating

    Shell Plating Amidships

Ø  Side Shell Plating Amidships

The thickness of the side shell plating within 0.4L amidships, as defined, is not to be less than obtained from the following equations or less than required 

t = 0.07L + 0.007s mm for L ≤ 150 meters    

                        

 Finalized side shell plating thickness = X mm

Ø  Transverse Framing

Where the side shell is transversely framed and the frame spacing adopted is greater than 760 mm (30 in.), calculations to show adequate provision against buckling are to be submitted.

Ø  Sheer Strake

In general, the thickness of the sheer strake is not to be less than the thickness of the side shell plating or less than the required deck stringer strake thickness in the same section being considered.

2.      Bottom Shell Plating

The thickness of the bottom shell plating within 0.4L amidships, is not to be less than that obtained from the following equations or less than required by 

Ø  Longitudinal Framing

t = 0.045L + 0.007s + 1.8 mm for L ≤ 123 meters       

                           = X mm

Finalized bottom shell plating thickness = X mm

3.      Shell Plating at Ends

Ø  Minimum Shell Plating Thickness

The minimum shell plating thickness for 0.1L at ends is to be obtained from the following equations. Between the midship 0.4L and the end 0.1L, the thickness of the plating may be gradually tapered.

t = 0.015L + 0.01s + 2.2 mm for L > 76 meters  

                          = X mm

Finalized shell plating thickness = X mm

Ø  Bottom Forward Plating

The thickness of the bottom forward plating, as defined, is not to be less than that obtained from the following equations. However, it need not exceed 25.4 mm (1 in.).

t = 0.055L + 0.01s + 1.0 mm for L ≤ 110 meters     

                       = X mm

Finalized bottom forward plating thickness = X mm

Ø  Immersed Bow Plating

Where the bow is of ship-shape form, the thickness of the plating below the waterline for the forward 0.16L is not to be less than obtained from the following equations, but need not be greater than the thickness of the side shell plating amidships.

t = 0.05L + 0.009s + 1.0 mm     

                                            = X mm

As this thickness of the plate need not be greater than the thickness of the side shell plating amidships t is taken as X mm.    

Finalized Immersed Bow Plating thickness = X mm