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Distinguished Contributor
PatrickEC
Posts: 195
Registered: ‎04-10-2012
Accepted Solution

Canadian Steel Code (CSA S16-09) - omega1

397 Views, 2 Replies
07-31-2012 03:52 PM

While reviewing steel code verification results after model modifications, I noticed the behavior that I do not understand and which is possibly a bug.

 

Below are the results for both models.

 

The first bracing point in both cases is at 4.27m (which is exactly where the calculation point is located, but it does not matter, I also checked the results for the point at 4.10m and observed the same behavior).

 

Forces and calculated coefficients are very similar with the exception of omega1.

 

Here is the relevant excerpt from the code:

 

omega-1_code.png

 

Based on this:

A) for Buckling Z:
Shear force Fy is zero over the section considered, therefore clause 13.8.5(a) applies. Bending diagram Mz is in double curvature and the ratio of the moments is around 1, so omega1 should be 0.4 - as in the first model and not 1.0 as in the second model.

B) for Buckling Y

Shear force Fz varies linearly over the section considered (indicating distributed load between supports), therefore clause 13.8.5(b) applies and omega1 should be 1.0 - as in the second model and not 0.61 as in the first model.

 

 

omega1_-_model1_-_steelres.png

 

omega1_-_model1_-_Fy.png

 

omega1_-_model1_-_Mz.png

 

omega1_-_model1_-_Fz.png

 

omega1_-_model1_-_My.png

 

omega1_-_model2_-_steelres.png

 

omega1_-_model2_-_Fy.png

 

omega1_-_model2_-_Mz.png

 

omega1_-_model2_-_Fz.png

 

omega1_-_model2_-_My.png

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Artur.Kosakowski
Posts: 4,777
Registered: ‎12-17-2010

Re: Canadian Steel Code (CSA S16-09) - omega1

08-01-2012 02:42 AM in reply to: PatrickEC

Patrick,

 

The calculations of omega1 is not fully automatic and it depends on the load scheme you selected. See the attached picture.

 

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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Distinguished Contributor
PatrickEC
Posts: 195
Registered: ‎04-10-2012

Re: Canadian Steel Code (CSA S16-09) - omega1

08-01-2012 08:01 AM in reply to: Artur.Kosakowski

These settings were indeed different in both models. Thanks!

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