Torsional Stresses and its prevention
A ship traversing a wave train at an angle will be subject to righting moments of opposite directions at its ends. The hull is subject to a twisting moment (torque) and the structure is in torsion. This is known as torsional stress.
Arrangements to compensate Torsional Stresses
The materials used in a ship’s structure form a box shaped girder of very large dimensions.
The side shell plating, keel and bottom plating, deck playing, hatch coamings, deck girders, double bottom structure, bottom, side and deck longitudinals and any longitudinal bulkheads assist in overcoming longitudinal stresses. Transverse bulkheads and deep transverses are efficient in preserving the transverse form. Plates, beams, floors,etc. all being securely bracketed together help to stiffen the plating against compressive stresses. Since water pressure is a major stress on the hull, and increases with depth, the bottom plating is heavier and the side framing size reduces with height above the bottom.
It is essential to prevent the various stresses causing deformation or possible fracture of the structure. This maybe achieved by increasing the sizes of the martial used, by careful disposition of the material.
Ref: Ship construction sketches and notes by Kemp & Young
