Equivalent Torsional Constant for two rectangular beam in parallel

[fl11]

Hi,

I have looked through all the forums and didn't find the answer to my question.

If I have two rectangular cross-section beams which work in parallel against torsion. I want to model them in Patran using a single beam with equivalent properties. This is easy to do for Inertia properties, but how can I calculate the equivalent Torsional Constant (J in Patran, K in Roark)?

I have looked in Roark, but haven't found anything, though some formulas seems to indicate that simply adding the J properties seems to be the way to go...at least for thin wall beams,but nothing for plain rectangular or round beams.

Do you guys have any clues and/or reference for that situation?

Thank you very much!

 

[40818]

I'm not sure that this is a specific question related to Patran. I would post this question in a different forum, (aircraft or mechanical).
Though if you have 2 beams why would you want to model them as one??

Without further details it is hard to establish you probelm, though if i imagine 2 beams parallel to each other and applying a rotation about the centre point between them (there shear centre) i would expect that you could simplify the problem to a couple applied to both beams, as they act independently to each otherabout a central axis. Though its a Friday night and (once again) i have had just a bit to much wine.

 

[fl11]

I think you are right. I should post that on another forum. Is there any way to redirect the post to another forum? I don't think it would be appreciated if I start the same thread in two forums.

Anyhow, you are probably right about modeling the two beams. It is more trouble but it solves the question. Still, some times, a cross section might contain a hole, so there is two separate areas and I would still need to find an equivalent Torsional Constant for those two sections.

 

[fl11]

I have started this topic on the Mechanical Engineering Other Topics forum at this URL:

http://www.eng-tips.com/viewthread.cfm?qid=217973&page=1

Please go there to participate in the discussion as it seems a better place to discuss this topic.

Thanks,