Unsupported Column length- Axial Force > Euler force

[LoneStarEngineer]

I have a building model in ETABS with 8 parking floors and 15 apartment floors on top. When I run the analysis and design for the structure, the columns near the ramps of the parking floors are giving out an error saying that " Factored axial load is greater than the Euler load".

I am positive that this is not true since my columns are 30"x30" and the euler force I hand calculated is way over than the factored axial force on the column. I think that the program is not taking the correct unsupported length of the column while calculating the Euler force.

While I know that ETABS does not consider the ramps as part of the diaphgragm, I have beams in both directions connecting the columns that also follow the slope of the ramps. So, I would think that the column would be braced by these beams and calculate the respective unsupported lengths. But this does not seem to be the case due to the error that the program is giving out after design.

Is there a way to check why this is happening. Am I missing something while modelling?
Appreciate all your answers. Thank you.


-Abrar

 

[chekre]

Check the unsupported length considered by the program. If the program is not considering the beams which will brace your column, then overwrite it. Otherwise, if the height is correct, then you have a big axial force which is exceeding the Euler force. Don't forget that the ultimate axial force is checked versus 0.75xPc and not 1.0xPc.

 

[serrojo]

The program reads the effective Length from the joints around the frame element, so you have to check if your desired lenght is correctly drawn.
you can select the column and see if it highlights as one element. If so try to select the beams(braces) and the column and go to "edit> Edit Frames> Divide Frames> by intersection with selected frames"

Hope to be helpful.

Best regards.

MSc. Eng. Serguei Joa
Tel: +5352460358
mail: sm.joa@bouygues.cu