Rotational restraint of flanges in I beam
Rotational restraint of flanges in I beam
(OP)
Dear all, just a quick question.....Basically, I have an I beam, and I want to find the shear buckling stress of the web. I want to model the top and bottom of the WEB with SPRINGS to take the rotational restraint of the FLANGES into account in the FEM program (Nastran). I am trying to calculate the K rotational restraint value to input into Nastran.
It will be in terms of a moment per unit angle of rotation per unit length???.
Any thoughts on this ?
Perhaps the easier way would be to model the flanges as beams connected to a shear web, and that's the way we normally do aircraft structure. But I was wondering if I could do with just springs and would prefer that.
Many thanks for looking into it.
It will be in terms of a moment per unit angle of rotation per unit length???.
Any thoughts on this ?
Perhaps the easier way would be to model the flanges as beams connected to a shear web, and that's the way we normally do aircraft structure. But I was wondering if I could do with just springs and would prefer that.
Many thanks for looking into it.





RE: Rotational restraint of flanges in I beam
in any case, springs connect grids, so the stiffness would need to reflect the grid spacing.
RE: Rotational restraint of flanges in I beam
I would think it would be a lot easier just to look up the research that has already be done rather than try to re-invent the wheel with an FEM analysis.
RE: Rotational restraint of flanges in I beam
Question: Why do you prefer to do it this way? Computer resources? easier to copy springs along a length and can place them strategically? I don't think I follow your desire.
Comment:
Really? For global models, maybe (I don't model an entire aircraft), but for local models, I usually model any stringers (longerons) and frames (with shear ties) as plates. Then I discreetly model the fasteners using beams and the Huth fastener values. I've seen this approach from several other analysts as well.
Garland E. Borowski, PE
Engineering Manager
Star Aviation