Structural Post-Processing Elements Structural Post-Processing Elements

MOSES has a concept of "pseudo elements" which can be used for structural post-processing. The pseudo elements are called sp_beams or sp_plates, and they are defined in the same manner as beams or plates except that the command BEAM is replaced with SP_BEAM or PLATE is replaced with SP_PLATE; i.e.

     SP_BEAM, ELE_NAME(1), ~CLASS(1), -OPT(1), *NODE(1), ... *NODE(m), \
     ELE_NAME(2), ~CLASS(2), -OPT(2), *NODE(n), ...


and there is an additional option which must be used:

     -ELEMENTS, :ELSEL(1), .... :ELSEL(n)

These commands create a pseudo elements which have all of the properties defined with their class and their geometry, but gets their load information from the elements specified via the -ELEMENTS option. Here :ELSEL(i) are selectors for the elements which will be considered to "be a part of" the SP_BEAM or SP_PLATE.

As mentioned above, these pseudo elements add nothing to the model - no stiffness, no weight, nothing. They are simply a useful way to look at parts of the model "in the large" for structural post-processing. In particular, suppose that one had a plate model of a semi-submersible. After a structural analysis, he has stresses in the plates, but that is it. Now, to really analyze this situation, one needs to check global buckling of the columns, etc. By creating SP_BEAMS of the various pieces, this can be easily accomplished. For purposes of structural post-processing pseudo elements are treated the same as structural elements. Thus, one can also find bending moments and shears in them, stresses in them, etc.