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DenisJaunin15-Moonstone
15-Moonstone
September 12, 2019
Solved

Crane formulas

  • September 12, 2019
  • 2 replies
  • 4080 views

Hello,
In the attached example I cannot execute the formula described in the spreadsheet in Table 5.1.
Maybe I'm the one who misplaced the formula or there's a printing error.
Sincerely.
Denis

Best answer by LucMeekes

That makes sense!

It also explains why I could not find what unit should be used for 'A'. But then the 'e' symbols in the formulae should be upright instead of italic.

Comparing with the English version of EN 1993-6:

- There the mu's are italic and e is upright.

whereas in the french (picture in the prime file) the e's are italic and the mu's are upright.

Is this (yet) another thing the French do opposite?

 

Luc

2 replies

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LucMeekes23-Emerald IV
23-Emerald IV
September 12, 2019

You're trying to add apples to pears. Mathcad will (fully rightly and fortunately) not allow that.

You're raising A to a power 3.015*mu.A and adding the result to 0.05 and subtracting 0.58*mu.A.

The unit of A  is mm, the unit of mu.A is 1 (unitless). This makes the first two terms of the expression to calculate c.xA unitless, the third is in mm. Apples and pears...

 

Most probably these are empirical formulae. Often they are NOT unit-balanced.... as in this case.

One way to use them is to work without units with these formulae. You also have to be aware that the various factors (such as 0.580, 0.148 etc.) may contain unit conversions, so you MUST supply the variables with values corresponding to the units that these formulae are devised/designed with. As there is no information on that in ENV 1993-6 (that is, I couln't find it), you'll probably have to look in ENV 1991...

 

Success!
Luc

 

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DenisJaunin15-MoonstoneAuthor
15-Moonstone
September 12, 2019

Thank you for your very complete answer.
That's exactly what I noticed about the units.
I tried to multiply each factor by a 1 mm unit, but it doesn't work either.
One surprising thing if we just look at the result of the last line, is this power after the units?

Denis

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LucMeekes23-Emerald IV
23-Emerald IV
September 12, 2019

You raise A to a power other than 1, this means that the unit of A (mm in this case) is raised to that same power.

What's surprising, is that this power (2.388)  is presented as 683/268 by the numeric processor. I could expect this from the symbolic process...

 

Luc

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Fred_Kohlhepp23-Emerald I
23-Emerald I
September 13, 2019

Your expression should not have the length "A", it should have "e"

Capture.JPG

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    LucMeekes23-Emerald IVAnswer
    23-Emerald IV
    September 13, 2019

    That makes sense!

    It also explains why I could not find what unit should be used for 'A'. But then the 'e' symbols in the formulae should be upright instead of italic.

    Comparing with the English version of EN 1993-6:

    - There the mu's are italic and e is upright.

    whereas in the french (picture in the prime file) the e's are italic and the mu's are upright.

    Is this (yet) another thing the French do opposite?

     

    Luc

    D
    DenisJaunin15-MoonstoneAuthor
    15-Moonstone
    September 13, 2019

    Hello FredKohlhepp, LucMeekes,
    Thank you very much for your explanations.
    I looked at the English version and it changes completely.
    What a shame for this transcription of a mathematical formula.
    With my thanks.
    Denis

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