Different direction of the arrow on two identical mounting.

[DenisJaunin]

Hello
I recovered these two images of a gallows.
One is the stem with constraints on the truss and the flat of selected.

The other is the same stem but in Assembly with screws against a wall.
Load conditions are identical in both cases.
How can you explain the different form on the two flats of selected.

The first to one "negative" arrow, the other "positive".

Kind regards.
Denis

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[gkoch]

Hello Denis,

I'd say it's coincidence.

It looks to me as if these pictures just show different Euler modi for a long thin body, so both shapes should be possible (and probably some more).

Regards,

Gunter

[DenisJaunin]

Hello Günter,

Thanks for your note.

I see on the images that the scale of deformation are 11 and 38 times

for a beam of 3500 mm long.

It seems to me that the most logical strain is the gallows 31?

Kind regards.

Denis

[gkoch]

Hello Denis,

I am not convinced that gallows 31 is more likely than gallows 11 in this situation.

If I remember correctly, for the Euler modi the probability is the higher the simpler the shape is.

In this case gallows 11 seems to be the most simple shape (for both ends being infinitely fix), while gallows 31 does a double bow.

But there might be influences that make one or the other more probable, depending on how fix the ends actually are.

Thanks,

Gunter