Modeling Errors
Warning #340
RBE3 using 123456 DOF coupling at the independent GRID points can produced unexpected results.
*** WARNING #340
RBE3 element 6300346 has nonzero weight at rotational (456) dofs of independent grids.
This practice may result in undesirable load distribution - use with caution.
Warning #1265
*** WARNING #1265
PSHELL 10003383 has thickness 0.0201 or less and bending properties defined. This can lead to matrix singularities, causing message 153.
If this element is intended to be only a membrane element, please leave MID2 and MID3 blank on the PSHELL data.
For thin skin elements, leave MID2 and MID3 blank on the PSHELL data.
Warning #1942
Confirm that Field 9, CID is specified with either 0 (zero) or the appropriate local coordinate system on CELAS GRID points. Below is an example of the OptiStruct output for the two types of modeling errors.
*** WARNING # 1942
CELAS2 8820024 references GRID data with different CD.
This may constrain rigid body motion
Elements
Do not connect CBEAM or CBAR to skin elements that have MID2 and MID3 blank on the PSHELL data, as this will cause mechanisms. Use RBE2 elements instead with 123 DOFs specified.
Rigid Body Modes
Welding Methods
Do not use welding methods that use MPC equations. This, in general, will give very poor rigid body modes that are not equal to zero. Use rigid elements instead.
Extra Rigid Body Modes
Do not use an RBE3 using 123456 DOF on the dependent GRID to only 1 or 2 GRID points with 123456 DOF on the independent points. Use of these types of elements can produce extra rigid body modes.
*** WARNING #341 RBE3 element 10159308 has only two nodes. This practice may result in undesirable load distribution - use with caution.
Use at least 3 non co-linear grid points with only 123 DOF on the independent GRID.
Poor Rigid Body Modes
CELAS elements between two non-coincident points will produce poor rigid body modes. Use CBUSH elements instead. The use of GROUNDCHECK will catch misaligned CELAS elements.
These elements can cause GROUNDCHECK to FAIL CELAS elements in this list are probably misaligned. Elem no: 1 type: CELAS1 Six rigid mode energies and ratios: energy - 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 ratio - 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 4.000E+00