Is there any way to define a full unsymmetric sub-matrix [B] in ANSYS?
Not in 11.0, but in ANSYS 12.0.1, this capability was added to the code. However, it was at the last minute before the code freeze, so it may not be documented in this production release. Therefore, it is technically BETA, but is available for SHELL181. A Word document and .PNG image file (the latter in case there is a problem viewing the MS Word file) are attached to this solution outlining the format used for the SSPB command. This command specifies a pre-integrated coupling stiffness for shell sections.
Please also see Knowledge Base Solution 738202 for an example of using matrix input to define the section stiffness of a composite element. Also, please set NROPT,UNSYM if using this unsymmetric matrix input.
The SSPB command enhancement is also shown below in ASCII text format:
SSPB, B11, B21, B31, B22, B32, B33, T, B12, B13, B23
Specifies a preintegrated coupling stiffness for shell sections.
PREP7: Cross Sections
MP ME ST PR PRN <> <> <> <> <> <> PP <> EME MFS
B11, B21, B31, B22, B32, B33
Coupling stiffness component (lower part of submatrix [B]).
Upper part of submatirx [B]
If the coefficients B12,B13,B23 are not defined, then a symmetric form of [B] matrix will be used. If any one of the coefficients B12,B13,B23 is non-zero, the submatrix [B] will be considered as unsymmetric.