Longitudinal Strength Longitudinal Strength

To produce longitudinal strength results, the user should issue the command,


     MOMENT, -OPTIONS

where the available options are:


     -WAVE, WLENGTH, STEEP, CREST

     -ALLOW, ALLOW_STRESS, ALLOW_DEFLECT

When it is issued, MOSES will include all applied loads, the ballast in all tanks, the defined weight, and the buoyancy in the strength calculations. The values used for the buoyancy are those of the current state, i.e., the buoyancy is computed considering all parts which are active, and the current draft, roll, and trim. The current state can be set with either an &INSTATE, EQUI_H, or &EQUI command.

It is possible that the shear curve will not close, particularly if the vessel is not in static equilibrium. To close the shear curve, one should either issue an EQUI_H, &EQUI, &WEIGHT -COMPUTE, or &CMP_BAL command, to establish equilibrium before issuing the MOMENT command. Issuing the command to establishing equilibrium on the command line directly before the MOMENT command will insure the system is in equilibrium.

If one is interested in longitudinal strength in waves, he should issue EQUI_H with the -WAVE data before the MOMENT command. If not, the vessel will normally not be in equilibrium and the shear curve will not close.

In applying the loads, the default procedure is to include a load even if all of its distribution is not applied within the geometric limits of the vessel. When this occurs, the overhanging part of the load is transferred as an applied load and moment at the vessel end. If the end of the load is forward of the beginning, the end is set to be very close to the beginning. When a load is completely off of the vessel, it is applied as a concentrated load and moment at the end, and again the shear and moment curves will not close. After the results have been computed, the user is placed in the Disposition Menu so that he can dispose of the results generated. The -ALLOW option is used to define the allowable deflection and stress in the vessel. Here ALLOW_STRESS is the allowable stress (ksi or mpa), and ALLOW_DEFLECT is the allowable deflection (inches or mm).