How to input C, D, E and F points of a L-section beam under bending?

Instead of using a PBEAM property, you can easily use a PBEAML property, as it already have the most common standard sections, and automatically computes stress points 1 to 8 for you, as the attached document from PBEAML help of OptiStruct.

How can you locate cdef points in L-section Explain clearly

How can you locate cdef points in L-section Explain clearly

Y and Z are the local section coordinates, as shown in the picture below.

The stress values are computed for the local Y and Z axis going through the section Shear Center.

Just like the image on the PBEAML documentation:

 

If you define points C, D, E and F like this, you will get the same results as teh PBEAML

Notice that PBEAML property already give you these points with no need of further definition.

 

PBEAM (elements 1 to 10)

PBEAML (elements 11 to 20)