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Thread: Calculating Safe Axial Load for Steel tube

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    Default Calculating Safe Axial Load for Steel tube

    Hi Guys,

    Can someone explain in layman's terms how the safe axial load (SAL) is calculated on steel tube based on its length.

    I have a data sheet for Type 4 tube that starts from 200mm and works its way up to 6000mm in 200mm increments. Each length has a SAL in kN. E.g. 200mm = 79.3kN, 400mm=76.5kN, 600mm=70.9kN and so on until you hit 6000mm= 4.3kN.

    I'm assuming Euler's formula is used in there somewhere but what am I missing? I've tried using the formula but I cannot seem to get it to correlate to what's on the sheet.

    Can any of my learned friends out there assist in explaining how they arrived at those figures.

    Cheers
    Jason

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    Hi Jason,

    The formula used is detailed on page 120 of the TG20:13 design guide and comes from Eurocode 3, it is more complex (and conservative) than Euler and gives very similar values to the old BS 5973 "Perry Robertson" method. It uses a lot of Latin characters so not easy to repeat here I'm afraid.

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    Thanks for the info mate.

    Unfortunately I don't have access to TG20 as I'm Aussie and our scaffold codes/standards aren't as technically detailed.

    Seems like I need to try and source a copy from somewhere.

    Cheers Jason

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    Track down a guy called Andrew Dobinson at Brand in Oz he may help you

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    Thank Alan will do.

    Cheers Jason

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    When the formula is written out for "As New" 2.0 m lifts:-

    Axial Loads.JPG

    I use MathCAD for this so I can make the job specific changes without having to redo the whole thing every time. It's worth running through one of your local designers, tho. Just to be sure safety and load factors correspond, putting in the right info for the type of tube you're using and that sort of thing.

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    That's awesome Nick. Thank you so much.

    Cheers Jason

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    Depending on where you are in Oz you could look up Jamie Robertson, I'm certain he'll have a copy of the TG20 design guide

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    Quote Originally Posted by steveprower View Post
    Depending on where you are in Oz you could look up Jamie Robertson, I'm certain he'll have a copy of the TG20 design guide
    Hi Steve,

    I spoke with Jamie today and he doesn't have a copy unfortunately. Well he does but it's a paper copy and he said it's that old its falling apart like the Dead Sea scrolls..lol

    You wouldn't have an electronic copy of the design guide by any chance?

    Cheers Jason

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    afraid not and the NASC dont produce an electronic copy for obvious reasons but you can buy the design guide on its own at the moment for £125.00 which i think is pretty good value dont know what P&P to Oz would be though

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