Elastic Critical Moment (Mcr)

[Juhiimi]

Hi!

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Where do we get the C1, C2 and C3(0 in most cases) values, for the different shape of BMD, for the calculation of the Mcr(LTB)?
I found the old table from the Eurocode 3 draft(ENV-1992-1-3), but if I use these values, and do a hand calc, I don't get the same result as the design programs that I use (LTBeam, AxisVM), and it seems like these shape factors are the only values they use differently.

This is from the old Eurocode:

And this is the formula I use:

 

[SWComposites]

There are several texts with beam formulas, including Roark, Formulas for Stress and Strain.

 

[canwesteng]

M.cr should come from the national annex of your country. You won't find it in the EC for this reason. If there is no national annex, I guess you are free to use something reasonable. I think you can find guides for BS 5950 freely online, and it would be what I default to.