I am trying to apply a force per area load on a series of nodes that lie on the edges of shell elements. The elements simulate floor beams on a fuselage (see the green elements in the image below).
I have created a surface and applied the load to the surface. However, each time I try to expand the load, I get an error message. Neither will the load show up in the *.dat file. I have already exhausted every possible check I can think of: making sure the nodes are associated, making sure the geometry and the loads are included in the appropriate bulk data group, ensuring the nodal loads are in the group, etc, and I still can't get it to work.
The only thing I can think of is that perhaps Femap is not able to apply geometric loads to nodes unless their corresponding elements are also associated with the geometry. Does anyone know if this is true?
Yes, without shell elements on the surface, FEMAP cannot expand the loads. For shell based loads like this, FEMAP needs the elements to calculate the effective area at each node, and then the load to be applied there. You can assocate the nodes along that edge to the existing line, and put a Force/Length load on the curve and it will expand.
Ah, okay. That makes sense, but it brings up another issue/question: how does Femap go about calculating the effective area for the nodes based on elements? Does it actually account for element geometry or does it mimic the PLOAD card by skipping to nodal loads?
My understanding is that the PLOAD card takes the pressure multiplied by the area on the element and merely divides it by four to determine each nodal load, ignoring element geometry. This has caused problems for me in the past when applying pressure loads to mesh areas that transition from coarser to finer where element geometries become irregular.