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(OP)
Hello all,

I hope that all my fellow engineers are keeping well and safe. I was looking to get some advice from well-seasoned aircraft stress engineers on this forum.

I have recently come across a problem where I have loads defined for points 1,2 and combined moments at the location where the structure is fixed (points 3,4). I hope you can see the picture which I have tried to attach. I am now assessing Section a-a of the structure for stability and strength (by calculating section properties: moment of inertia, neutral axis etc.).

Would it be acceptable or conservative if I took a 60/40 load and moment split to obtain the loads at Section A-A? So the loading will look something like (Fx1+Fx2)x0.6, (Fy1+Fy2)*0.6 ... Mx x (0.6), My x(0.6) and so on?

Or

Do you suggest I resolve loads from Points 1 and Point 2 onto the neutral axis and obtain loads of Section a-a that way? Please keep in mind that the structure is fixed at points 3,4.

What are your thoughts? Looking forward to hearing from you.

Many Thanks
Regards,
Sam

No, you need to do a proper force balance analysis, or if the structure is indeterminate run a FE analysis.

is this a D-nose ?

are points 3 and 4 fixed or pinned ? is point 4 fully pinned, of is it reacting axial (y-direction) loads ?

do you have generally applied loads over the whole volume or on the surface (like aero-pressure ?

SWC is correct in that you need to start with a free body analysis of the applied loads. sum forces about point 3 … this'll tell you the load at point 4 and so AA.

and I'm not seasoned … just pickled.

(OP)
is this a D-nose ?
No it's a test structure, can't give more details due to NDA and IP.

are points 3 and 4 fixed or pinned ? is point 4 fully pinned, of is it reacting axial (y-direction) loads ?

The points are actually bolted onto another piece of structure which is free to move in the z direction!

do you have generally applied loads over the whole volume or on the surface (like aero-pressure ?

Yes for panels but not for this structure.

Thanks for getting back!

then all we can tell you is calc the free body of the applied loads and the reactions at 3 and 4. do you know how to do that ?

All we know is you've got some generalised structure with some generalised loads. the structure is supported at two places, with 2 inplane reactions at both points (I get this from your later reply, "fixed" usually means reacts moment as well as forces). this is redundant, but you could say that 4 reacts only Y load (because of how you've shown it connected to the rest of the structure) and so it becomes statically determinant.

(OP)
Thank you for all the responses. I will now look at now working out the reactions at 3 and 4.

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