A quite simple question about reactions in bolted joint

[eli28]

hello everybody,

I graduated long ago, and I am trying to figure out how to calculate reactions in bolted joint, so I will be able to know what is the external tensile load on each bolt and in addition the shear force that is actually the outcome of a friction generated by the pressure the bolt exerts.
I am trying to draw a free body diagram of a quite simple problem, but I find it difficult to solve since there are only 3 equations and 4 unknowns.
when I try to assume that as a result of symmetry the right reactions = left reactions I get a contradiction while formulating the equilibrium equation in the X direction.

 

[eli28]

rb1957
I think I don't understand what you mean by neglecting Fy/2 reactions...I included Fy external force and from equilibrium equations I find p*cos(phi) = Fy/2.
Can you tell me why I can't solve it by statics? I succeeded...I can write down the equations and send it.

 

[eli28]

BrianE22
Can you please draw the non-zero moment reactions at the bolted connection in a simplified diagram?

 

[goutam_freelance]

Here is the simplified FBD

F_b=force applied by bolt head on component
F_m= Normal force applied by supporting structure on component
F_f=frictional force applied by supporting structure on component
M= moment applied by supporting structure on component(to balance moment of F_y).


Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[rb1957]

eli28 ... the simplest reaction to the applied load, Fy, is Fy/2 (vertical) at both fasteners. This could be resolved into vertical and shear reactions of the bolts.

I'm not saying this is THE solution, it assumes zero friction. Friction would incline the two reactions, making an isosceles triangle.

goutam ... I'd adding a prying force on the flanges (make your "M" a couple) ...

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

 

[hydtools]

Cut the fbd in half through the plane of f_y. Translate the reactions to that section.

Ted

 

[eli28]

goutam_freelance
You added a "pure" moment to the FBD, while in my opinion the structure reasonable reactions are only forces. In my opinion, if we add a force in the flange's edge (something that is reasonable if we take in account that the structure isn't infinitely rigid) we get a resistance to the moment created by Fy force, but the problem will no longer be simplified. I am looking forward to read what you think.

 

[goutam_freelance]

if we add a force in the flange's edge

Actually there will be distributed force at the contact surface whose net effect will be to resist moment produced by F_y plus bolt preload and external load F_y. But in my 'simplified FBD' I have included an effective resisting moment(M) at the bolt CL which is statically permissible.
Yes the problem is not simple as I had pointed out in my first post. Better to do a FEA analysis to get the complete picture.


Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/