| Part of a series on vessels'
Ship loads come in a variety of forms, from the environment, operation, and loading of the vessel.
Induced or present in the vessel while it is at rest.
A vessel in motion will experience a number of dynamic loads as the result of machinery vibrations and seaway interactions.
Waves induce dynamic loadings both by induced variances in bouyancy along the length of the hull and water impacts from the resultant heaving, rolling, and pitching. Waves may vary in frequency, duration, height, and direction. An approximation of wave-induced longitudinal loading can be estimated by considering the ships hull centered on the crest or trough of a ship-length wave, and calculating the equivalent static stresses (i.e., as per Murray's method). While this number is quite the abstraction from a truely representative wave-interaction analysis (tedious, at best), the calculated number can be compared to calculated numbers for existing vessels which have proven sufficient in their service histories.
High frequency loads, or common vibration, can be amplified and transmitted by structure; structures exposed to vibrations near their natural frequency can 'pick up' the vibration (resonance). This may be felt on many vessels, for example, as a shudder in a vessel as it accelerates & the engines rpm passes through the natural frequencies of structural elements. High frequency dynamic loads increase displacement & deflection of structural members, potentially leading to or accelerating fatigue failures.
Global loads act on the entire "ships girder", the vessel as a whole.
Loads experienced by stiffened panels, girders, beams, & stringers.
The most severe load expected on a given member, to which the member will be sized/designed.