(Section Load manipulation) Advice/Steer request! 1

[Studentforlife]

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

 

[SWComposites]

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

 

[rb1957]

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.

another day in paradise, or is paradise one day closer ?

 

[Studentforlife]

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!

 

[rb1957]

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.

another day in paradise, or is paradise one day closer ?

 

[Studentforlife]

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