Concrete fence posts for fruit training- post weaker at wrong 90 degrees?

[Safety First]

Just set a pair of 9' posts into the ground at the allotment, 3' deep in concrete. Plan is to bolt 1" x 1.5" batten into the slot that the fence panel usually slides into. Same opposite side. Then with screw eyes and turnbuckles I'll strain 4 horizontal wires across for wife's fruit bushes to grow up and across... Posts are 11 ft apart...

However, now that I've done it, ... have I done it wrong?

The wires will be pulling the posts together at 90 degrees to the direction that the wind normally strains the posts. I.e., the panels don't pull the posts inwards do they?...but the wind occasionally pushes the posts perpendicular to the panel directions.

Are the posts going to crack given a constant strain of the wires? I have no idea of the force required to hold wire straight, bushes up, or posts cracked...

Should I brace the posts with a batten across the top- between the posts?

Would rather not clutter the growing area with diagonals of any type...

Someone with more knowledge of what these posts can deal with might advise, please?

And thanks!

I wouldn't really mind that much but the digging nearly killed me as did lumping the posts about.

Tom

 

[sodthisforfun]

I should imagine your posts and batten will be plenty strong enough. The wind will go straight through the fruit bushes (as barely no leaves) when it's at it's strongest, ie, the winter and even in the summer on a rare windy day, full of leaves I should imagine they'd not beat concrete.
If really worried, yes, put a batten horizontally at the top, but I think what you've done should suffice imo.

 

[big-all]

simple answer
do not panic as sod this forum says minimum wind loading and indeed your posts will never crack otherwise every concrete post would crack at ground level with the heavy wind load from fence panels
and after say a year or two there is more than say 50mm pulling together then a bit off [19x38/20/25x44mm] tile baton flat on will solve it

 

[jasonzyx]

Are people ignoring the weight of the bushes and any fruit on the horizontal wires?
It's not just the strain of the wires, but the additional weight of the vegetation and fruit.
The additional weight of fruit regularly snaps branches of trees.

 

[Safety First]

Thanks fo all input.

It's not the fruit bushes acting as fence panels and giving the posts too much demand that concerns me. They won't, as you say, make anything like the sail that a panel could.

Its that the posts are constantly being pulled at 90 degrees to their normal load direction.

If the posts are 'H' in section, and normally the loading is in this direction -> H -> but only when the wind blows!

I have put them under constant strain in this way ...
\/
H
\/

Is it like the old reinforced lintels that used to have the bar ofset- there was a 'way up' to them. They were utterly rubbish, if you put them the wrong way up. Perhaps fence posts are different at 90 degrees out of normal plane? Anyone ever cut one - knows whats inside maybe?

 

[sodthisforfun]

Are people ignoring the weight of the bushes and any fruit on the horizontal wires?
It's not just the strain of the wires, but the additional weight of the vegetation and fruit.
The additional weight of fruit regularly snaps branches of trees.

Nope
I've grown many fruits on wire, tied around just canes shoved in the earth. Doesn't snap nowt.
It's not trees either, it's fruit bushes that the OP is talking about. Presumably things like raspberries.

Back to the OP, if you're worried, use the batten you were talking about. I still think you're ok, concrete & wire is pretty strong stuff. Just make sure you use decent galvanised wire if you've not already thought of it, something that won't rust so quick anyway.

 

[conny]

9' posts in 3' of concrete are not going to move without a JCB hitting them. You have nothing to worry about and don't need the cross brace.

 

[Safety First]

9' posts in 3' of concrete are not going to move without a JCB hitting them. You have nothing to worry about and don't need the cross brace.

I suspect you are right... and they did noticeably seem to stiffen up even more after day 2 or 3. That said by the time I was tightening the turnbuckles the posts started to deflect all of.......about 9mm.....
But then part of the issue was the constant loading (without) the cross member across the top. With the cross piece across the top, in place before tightening the wires, the posts deflect almost nothing....so should not be under constant one-sided loading.