Torsion verification: EN1993-1 Vs BS5950

[Ricardo.Dias]

Hello.

I was designing a structure with the BS5950 code, when I realized in something strange: in certain elements with open sections (HEB), the torsion was not checked in the Robot steel design module.

I made a small example, with a cantilever beam: length equal to 0.5meters and the section is HEB200. Applied load: distributed torsion equal to 50kN.m.

When comparing the design by the EN1993-1 (image 1) with the design made by BS5950 (image 2), I realize that the verification of the torsion force is not being carried in the BS5950 calculation.

There is some error which I can be doing, or the Robot does not verify the torsion in the BS5950 code?

Thanks. 

[Artur.Kosakowski]

The torsion verification is not included for BS5950.

You can check the values of torsional stress caused by tosional moment in the stresses table.

[Ricardo.Dias]

Ok. One doubt: I view the stress caused by torsional moment (stress tables - image 3) and compared with the stress analysis for bars also made in the Robot, and I can't find the same value of stress in the bar's section (image 4).

This is because the formulations used in each case are different? I have only one load case.

Thanks.

[Artur.Kosakowski · Accepted solution]

The value in the table is calculated with use of the approximated formula from “Theory of Elasticity” - Timoshenko, Goodier - McGraw-Hill, 1951

I-SECTION:

h   -    web height
ea -    web thickness
es -    flange thickness
b   -    flange width

Wx     -    torsional modulus (tmax=Mx/Wx)

Wx=	Ix / max(ea,es)

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