Column Critical Buckling Loads - Page 4

 Curbie wrote:

Working it backwards to find the 'error',

(34000/1.9)*(1-0.5*X) = 10994
-.5*X = 10994*(1.9/34000)-1

X = .771259

Which is almost exactly 101.8/132

So in order to get the 'answer' of 10994, the original calculation would
have to have been...

(34,000/1.0)(1 - (1/2)(101.8/132)) = 10994.42

Without the square.

So now you'll have to decide if the 'error' was in the calculation and
the right answer should have been 12,573, or the 'error' was in putting
the superscript '2' indicating the quotient of (101.8/132) is supposed
to be squared.

Probably the person working the example simply forgot to square the
quotient and came up with the wrong answer and the right answer is
12,573.  Does the rest of the text show that that term is supposed to be
squared?

daestrom

  daestrom,


The next two examples that they give uses a larger columns with the
same formula (Ys / FS) * (1 - (1 / 2) * (S / SC)^2)
Ys = Yield Strength
FS = Factor of Safety
S   = Slenderness Ratio
SC = Slenderness Ratio Critical

My spread-sheet agrees those results using the same formula with their
new variables so it seems the results given for the first expression
was wrong.

I'm easily confused so when something doesn't make sense my mind seems
to fixate on it to the exclusion of all else that is related. I
generally don't pursue information posted on a site that contains an
error; my mind fixates on the error and questions the validity of
everything else. I've decided to press on with that site, the subject
has such specialized and limited interest that I've only found four
other sites with examples (and issues of their own) to learn from
(beggars can't choosers).

Hopefully between the four incomplete spread-sheets I'll be able to
fill in the blanks to make one complete sheet that both make sense to
me and can be verified with on-line calculators?

Neon John suggested I email them and ask for clarification (this was
before I knew it was an error), hopefully they can clean it up for
future readers.

Before I can play with wind-turbines I need to understand this stuff,
kind of a slugfest, but "welcome to my life".

Thanks for the math check.

Curbie