strange binding reactions

[Giacomo Lepore]

Good morning to all,
I press that the question is rather stupid, but as the answer is counterintuitive I would try to understand.
I have a beam with three screws as schematized in the image. against my imagination, solving the hyperstatic beam exercise, the most stressed screw is the central one (traction or compression depends on the direction of force, but this is not the problem).

I don't have much doubt about the correctness of the solution, but why would I never come?

 

[gerod]

probably because it would be said that the central one could also be removed? bolted unions on plates consider that the plate is rigid enough not to deform. in this case instead create a tension due to the deformation of the beam.
then the screw is a zipper and behaves as such.

Hi.

 

[AlbertoC]

deformed by the idea of the left moment of the zipper sx.
notice the actions on y to the sx and central hinges.
flying with ftool, great free program:finger:

 

[AlbertoC]

deformed by the idea of the left moment of the zipper sx.
notice the actions on y to the sx and central hinges.
flying with ftool, great free program:finger:

Bye-bye
What did I write? :biggrin:
the above software is ideal for students (but not only )...I had had it in my time!https://web.tecgraf.puc-rio.br/ftool/ftooleng.html
semplice e gratis :finger:

 

[gerod]

you had written foot!!! !

 

[Giacomo Lepore]

ftool, great program.
In fact if you see my first post, the screenshots are taken just by ftool.