Slenderness ratio limit EC2 - nominal stiffness vs nominal curvature

[stroxy]

Is the slenderness ratio limit λlim calculated differently for nominal stiffness method and nominal curvature method by the program? The same column is a short column when calculated using nominal stiffness but slender ( very very slender) using nominal curvature.  Excerpt from calc notes attached

[Artur.Kosakowski]

Could you attach the rtd file(s) with these columns please?

[stroxy]

File sent by email Thx

[Artur.Kosakowski]

Stroxy,

Try this approach please:

1. Convert generated code combinations into manual combinations

2. Import these combination s instead of simple load cases

3. Design the column

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.

[stroxy]

Thanks Artur

Couple of observations.

1. Generating manual combinations from the automatic combinations did not produce the same number of combinations. I had wanted to manually select the combinations from the forces envelope created using full automatic combinations, but realized some were not available to be selected for manual generation.

2. Reducing the number of combinations through the groups and relations tabs did resolve the problem however.

Many thanks for your efferts.

[Artur.Kosakowski]

Is the slenderness ratio limit λlim calculated differently for nominal stiffness method and nominal curvature method by the program? The same column is a short column when calculated using nominal stiffness but slender ( very very slender) using nominal curvature.  Excerpt from calc notes attached.

Improved in Robot 2015.

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.

[a54249]

Hi,

I'm using Robot 2015 and I'm having the same problem (the slenderness ratio limit is different in both methods). The results obtained by the nominal stiffness are in accordance with the obtained by my manual calculations, however the limit obtained by the nominal curvature is a lot different. Should this be happening? If not, ideas why this is happening? 

(.rtd file in the following link https://www.dropbox.com/s/duir8gftdg1vzwe/P.2012.13.E_Volume_DIM.rtd?dl=0)

[Artur.Kosakowski]

Try the following steps:

1. Export the column you make the comparision for from a model to the RC Column Design module with one selected combination only

2. Calculate it with nominal stiffness and freeze reinforcement

3. Check lambda_lim

4. Switch to nominal curvature

5. Calculate the column agian (with frozen reinforcement)

6. Check lambda_lim

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.

[a54249]

Thanks for the quick response,

I tried the proposed method and the result is the same (see attached image).

[Artur.Kosakowski]

Please follow these steps:

1. Open the file you made the previous test and calculate the column with nominal stiffness for the same combination and frozen reinforcement

2. Delete the whole model

3. Save it under a new name

4. Calculate the the column with  nominal curvature for the same combination and frozen reinforcement as above

5. Save it under a new name

Compress and attach both files.

[a54249]

Thanks again,

Both files can be obtained hrough the following link:
https://www.dropbox.com/s/9rrsxbug443ufq2/PComplete_Single.zip?dl=0

[Artur.Kosakowski]

Please install SP4 for Robot 2015. It should be available for download in approx. two to three weeks.