[Help] Confusions regarding ship stress calculating equipment

Engineering Marine Engineering
1

Can someone please answer these questions of mine:-

  1. Why there are TWO sets of values of maximum permissible shear forces and bending moments on a hull stress indicator and what do these stress values represent?

  2. Why the maximum permissible Shear Force and Bending Moment values may be adjusted on the advice of the classification society during the service of the ship?

  3. What are the typical assumptions made by a loading instrument with respect to the wave profile for assessing ship stresses when the ship is at sea ?

  4. Why are there consistent inaccuracies between the draughts as calculated by the ship stability software and the draughts as read, despite dock water density being correctly input into the programme on each occasion? And how can they be compensated to ensure that the draughts as calculated by the software are the same as the draughts as read.?

2

If you cut a pencil in half with a pair of shears it’s shearing forces if you break it in half by holding the ends and bending it’s bending moments.

#4 Most likely because the weights are not accurate. If the weights are gotten exactly correct the calculated will match the actual. In practice the weights will never be exactly right.

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3

Thanks, can you answer the first 3 questions too?