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Web stability under force - Buckling coefficient kF (EC3-5 cl.6)

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Message 1 of 4
Anonymous
396 Views, 3 Replies

Web stability under force - Buckling coefficient kF (EC3-5 cl.6)

Hello!

How is kF factor (EC3-5, fig. 6.1, p. 26) calculated in Detailed Design of Member Verification of Steel/Aluminium Design?

kF.png

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I was veryfying results from Ex. 9.2 (Arya, C. (2009) Design of structural elements, pp.389) for web buckling of an UB356x171x45, sitting on 125 mm bearings on both sides. Given ss=125mm and hw=332,6mm, the kF should be 4,25 (see the link above for the calculations).

 

Detailed design.png

 

In RSAP, however, given ss = 12,5 cm the kF becomes 2,75. I was fiddling with numbers and it seems to me as if RSAP is using hw = 100 cm (if indeed the expression given in the beginning is used), because the value of ss = 37,5 cm gives the kF = 4,25 (see the picture below) that I was trying to attain in the beginning.

 

Detailed design Results.png

 

This makes LamF and therefore Xf factors and ultimately FRd significantly different (handcalculations for ss=125mm give FRd=237,6kN). What am I missing here?

3 REPLIES 3
Message 2 of 4
Artur.Kosakowski
in reply to: Anonymous

Thank you for indicating this situation.

 

The formula for Kf entered in the internal code of Robot is by mistake defined as kF = 2.0 + 6.0*(ss+c/hw)  instead of kF = 2.0 + 6.0*(ss+c)/hw. This needs to be corrected.



Artur Kosakowski
Message 3 of 4
Anonymous
in reply to: Artur.Kosakowski

OK, good to know!

Thank you.

Message 4 of 4
Artur.Kosakowski
in reply to: Anonymous

Corrected in SP4 for RSA 2016.

 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.



Artur Kosakowski

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