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Saadat

Checking of steel I or H cross-sections for axial load and bending effects

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Hi All,

 

I am trying to check an existing result using of an I-cross-section subjected to combined axial compression and bending. According to the EN 1993-1-1 (2005) code it is required to check the cross-section's capacity to withstand combined effects of compression and bending first then move to member level. Formulations set out in section 6.2.9 of EN 1993-1-1 (2005). 

In equation 6.36 pp 54, procedure to calculate the reduced moment about y axis (MN,y,Rddue to the effect of compression is provided. This equation is as following,

 

MN,y,Rd=Mpl,y,Rd(1-(NEd/Npl)/(1-0.5*a) <= Mpl,y,Rd

 

where, a = ((Gross Area) - 2*(section width)*(flange thickness))/(Gross Area)

 

Normally for design purpose, it have to be NEd<Npl always. But for an existing result while checking if NEd>Npl the value of MN,y,Rd becomes negative which seems irrelevant. My question is how to sort this problem? Should I take ratio of NEd/Npl maximum equal to 1 or take the absolute value of the moment ignoring the negative? As the axial compression is very high the moment magnitude will be small.

Any help would be highly appreciated.

Thanks, 

Saadat

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Hello, Saadat!

 

If you have Ned / Npl,Rd >= 1,0 then your member is failing in compression, thus, there is no need to check interaction as cross-sections resistance is already insufficient for axial load alone. 

 

Have a great day,

Reinis

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Hi Reinis,

 

Thanks a lot for your reply. :) 

 

Cheers, Saadat

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