STRESSES ON A SHIP

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upper edge would crumple up and the lower edge break asunder. The
girder would be fractured and shotf signs of strain.

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OIL

Fig 3 —GWer Strengthened with Flanges.

By stiffening the edges of the plate with angles as in Figure 3, the
girder will now be able to resist distortion due to the weight C. The
vertical plate is called the web of the girder and the edge angles its
flanges. The web could now be made thinner and the arrangement
gives a more efficient girder than the simple plate

A converse condition would arise when the girder, supported at its
middle point At is called upon to support loads B and G at each end

as in Figure 4. The upper edge will now be under tension and the lowei
edge under compression, with the neutral axis DE between.

A ship when afloat is subjected to similar stresses, not merely by the
loads placed on board but more seriously when working in a seaway.
Figure 5 represents a ship supported at each end on the crests of two
waves, the weight of the hull and its contents being represented by a

Hg. 5.—Sagging.
load at G. The load is, of course, not concentrated but is distributed
over the length in various degrees of concentration. The upper edge
of the ship is under compression, and the lower edge under tension