Static stresses and constraints

These stresses are measured when the ship is not under way. They are often caused by a poor longitudinal distribution of mass. Even if the ship's total weight is balanced by the total force of buoyancy, these forces may not be distributed evenly along the full length of the ship.

Hogging

Hogging and sagging can be amplified by the movement of waves passing along the hull. A crest of waves at each end of a ship combined with a trough amidships will amplify sagging, while a crest amidships combined with a trough at both ends will amplify hogging.

The stresses caused by these situations can be calculated using the load curves table, the stress and sheer curves table, and the bending moments table. Manual or electronic calculators also exist to find the value of the stresses on the hull. The maximum permissible stress values can be found in the ship's stability book.

Dynamic stresses and constraints

When a ship is under way, some situations create additional stresses. They are caused primarily by the effect of waves on the hull in rough seas. Two of these are pounding and panting.