Steel member verification - example that verify in Robot but not verify in EC3

[Anonymous]

Hi,

I have an exemple that I'd like to share and discuss because I think its very important an serious matter.

An beam column subject to axial and bi-axial bending with diferent moments at ends:

Data:

HEB400

L=7 m

S355

Axial forçe ELU = 1000 kN

My ELU = 810 kNm (at left end)

Mz ELU = 190 kNm (at right end)

Member type:

ly=7m

lz=7m

lLT=7m (lateral buckling)

load level = centre of gravity

load type = linear moments (My and Mz)

Eurocode 3 - Detailed Method

Method 2 - annex B

Results of Calculations:

RACIO = 0.95

Manual calculations:

RACIO = 1.476

The robot do not take in consideration the Mz moment and this is very serious because its necessary to verify the stability of MEMBER (not the sections only)

I'd like your help to this issue.

Sergio Vale

[Artur.Kosakowski]

Could you attach the rtd file and the hand calcs for the reference please?

[Anonymous]

Hi,

here is the attached file and the resume of manual calculations (because i solve with my personal spreadsheet).

You need to rename the file .txt to .rtd because I couldnt attaxed the rtd file (sorry).

Thanks

Sergio

[Anonymous]

Hi,

I adviced to see the ECCS book "Rules for Member Stability in EN 1993-1-1 - Background documentation and design guidelines" (ECCS n. 119) , example 5 page192.

Thanks 

[Artur.Kosakowski]

As far as I  can see you use EC3 with the UK NAD and the version of Robot is 2012.

I'm attaching the screen captures from v.2013SP3. As you can see the stability check is with consideration of both My and Mz bending moments.

In case when the verification is done in the point where only  one bending moment exists (x=0.0L as shown on the left picture) the stability check formula is displayed incorrectly (missing part with Mz) yet the final value is correct 1.37. To illustrate this I forced the verification at x=0.5L (right picture) and as you can see the stability check formula includes both My and Mz and the final value is exactly the same as previously (1.37).

The display of the formula in situations when there is only unidirectional bending in the analysed cross section is planned to be addresses in Robot 2014.

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.

[Anonymous · Accepted solution]

Hi Artur,

OK, the problem is my robot version, I'll change that.

Thanks very much for your help and best regards.

Sergio Vale