Bending of beam under pure tension 1

[Nougatti]

Hi there!

Given a beam/profile like this

With a force applied normally to one end and given no degrees of freedom at the other, the beam is experiencing pure tensile stress.
It should be, anyway.

In reality, what happens is that the beam bends drastically outwards and experiences bending.

Can anyone share some insight into why this happens and how I can avoid it?

I have a gate where the back plate (not exposed to water pressure) is holding the front arced plate (exposed to water pressure) together.
I wanted to stiffen this large plate up with a few bars to avoid it being so flimsy, but it makes the whole back plate bend outwards.

With best regards
Daniel

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I am Norwegian.
I design mechanicals for hydroelectric powerplants.
I use NX 8.0.3.4 and ANSYS 15
----------------------------
Tom you can't knit at these speeds! Nobody can! DON'T BE A GODDAMNED HERO TOM!

 

[Nougatti]

With both sections combined, the entire gate is about 7 metres tall. The water pressure is at 16.5 mwc, excluding the 1.2 load factor.
The strength lies in the arced shape of the front plate.
The larger the radius of the front plate, the thinner the structure and the more "stretch" of the back plate under pressure.
The smaller the radius, the closer we are to a "perfect half circle" which leads to less stretching of the back plate, but also makes for a stupidly overall thick and hard-to-handle structure. This also leads to trouble with the flat, pressure-affected top plate, which would have a very large span.
I've got a good compromise with a radius of around 6-6.5 metres. This makes the gate a little under 2 metres thick.
FYI, the gate will only be maneuvered under equalized water pressure (no flow).

---------------------------
I am Norwegian.
I design mechanicals for hydroelectric powerplants.
I use NX 8.0.3.4 and ANSYS 15
----------------------------
Tom you can't knit at these speeds! Nobody can! DON'T BE A GODDAMNED HERO TOM!