Page 160 - Introduction to Naval Architecture
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146 STRENGTH
Until 1960 the classification societies used tables of dimensions to
define the structure of merchant ships, so controlling indirectly their
longitudinal strength. Vessels falling outside the rules could use
formulae such as the above in conjunction with the standard
calculation but would need approval for this. The societies then
changed to defining the applied load and structural resistance by
formulae. Although stress levels as such are not defined they are
implied. In the 1990s the major societies agreed, under the International
Association of Classification Societies (IACS), a common standard for
longitudinal strength. This is based on the principle that there is a very
remote probability that the load will exceed the strength over the ship's
lifetime.
The still water loading, shear force and bending moment are
calculated by the simple methods already described. To these are added
the wave induced shear force and bending moments represented by the
formulae:
where dimensions are in metres and:
