interpreting alpha_cr values EC3

[Mohamed_AbdElAziz4TPC2]

hi everyone,

I am getting very low alpha_cr values  of 0.2 under own weight case 1

then zero or N/A under vertical dead and live load cases

then very high values under various combinations

1.can someone help interpret it ? and should I get it for load cases or combinations?

2.is buckling analysis necessary to get correct values ?

I attached model and screenshot

thank you for your time

[Simau · Accepted solution]

@Mohamed_AbdElAziz4TPC2 

Except for the selfweight, it is not necessary to calculate alpha cr for simple cases, but only for combinations.
The interpretation of alpha cr must be done in parallel with the deformation of the structure. The alpha cr that must be looked at is the one whose mode deformation corresponds to a global buckling.
Avoid separate structures, because the Alpha cr coef found will be applied to the loads of the buckling structure, therefore not easy to manage with several structures on the same model
Example: screenshot for combination 102

[Mohamed_AbdElAziz4TPC2]

thanks @Simau I appreciate it