Q: We conducted the longitudinal strength assessment of a ship with three different softwares, and the maximum bending moments, calculated by two are quite similar. But comparing these maximum bending moments to the ones computed in the MOSES show large deviations. As you said on your homepage a MOSES uses a different integration method than that described in the Principles of Naval Architecture. What kind of integration method is used?
REV 7.06

A: MOSES adds trapezoidal loads on a beam using the exact solution for the bending and shear in a pin ended beam. In other words, go to the old edition of Roark (fourth edition). Add the solution of table III.14 and table III.16. This will give you the moment, shear, and deflection at all points on a simply supported beam with a trapezoidal load applied. Now, for each load (weights and buoyancies) you simply use this formula to get the total shear, bending, and deflection.

Notice that since we begin with a pin ended beam we always get zero moment at the ends but the shear will be zero only if the body is in equilibrium, under weight and buoyancy.

This algorithm is iron clad; i.e. it is always correct. If you have differences with other programs then the difference is due to the way either the buoyancy or weight is modeled (or of course, the other program could be wrong).