Page 375 Direction of Ship Motions
The job of the designer is to translae the loads resulting form the movement of the ship into loads applied to the pressure vessel that is stroed either at or below decks. The ship itself will rotate about its own center of buoyancy (C.B.)dependingon the diredtin of the sea and the ship's oritatin to the direction of sea. The vessel strapped toits deckis in turm affected byh its locatin in relatin to the C.B. of the ship. For example,if the C.G. of the vesselis located near the C.B. of the ship, the forces are minimized. Thw farther apart the two are i relatin to each other, the more pronounced the effect on the vessel.
the ship's movement translate into loads on the three pricipalaxes of the vessel.Saddle and lashing must be stroung enugh to resti these external forces without exceeding some allowable stress point in the vessel. The poing of applicatin of the load is the C.G. of the vesssel. these loads addect the vessel in the same mannner as seismic forces do. In fact, the best way to think of these loads is as verticala dn horizontal seismic forces. Vetical seismic forces either add or subtract to the wiengt of the vessel. Hotizontal seismic forces are either transverse or lingitudinal.
The X,Y, and Z axis translate into and are ewuivalent ot the follwoing loading in the vessel:
X axis: horizontal transverse.
Y axis: correspouds tovertidcal losds by either adding or subtracting form the weight of the vessel
Z axis: longitudinal axis of the vessel. All A azix are longitudinal loadings
Load Cobinations for Sea Forces:
1 dead load + sway + heave + wind
2 dead load + surge + heave + wind
Stephen
Leonard Stephen Thill