I am trying to check Bucking analysis results, so I modeled cantilever steel column with cross section I add to the Indian section library called “100CU82x2.7”, and I performed buckling analysis. I add the section as a new raw in the Indian section table using the following data: -
- Name and staad name 100CU82x2.7
- Area = 7.221 cm2
- D = 100 mm
- B = 82 mm
- T = 2.7 mm
- R = 3.0 mm
- Iz = 101.361 cm4
- Iy = 51.664 cm4
As per Euler theory for buckling analysis, buckling happens around the weaker axis So, to find the buckling factor Pcr: -
Pcr = (3.14 ^2 * E * I) / (K*L) ^2
In our case, we have
I major = 101.361 cm4
I minor = 51.664 cm4
L = 1000 cm
K = 2.0 for cantilever column.
E = 20.5e6 N/cm2
Around weaker axis Pcr = 5127.0 N
Around stronger axis Pcr = 2613.25 N
Pcr = 2613.25 N
And the applied Node load equal Pac = 1000 N
So, the Buckling factor = Pcr / P ac = 2613.25 / 1000 = 2.61325
After performing buckling analysis in Staad Pro. And checking the cantilever properties, the program changed the Inertia properties to the following value: -
- Iz = 121.361 cm4
- Iy = 49.5613 cm4
And using these values we get: -
Around weaker axis Pcr = 6138.64 N
Around stronger axis Pcr = 2506.89 N
Pcr = 2506.8959 N
So, the Buckling factor = Pcr / P ac = 2506.89 / 1000 = 2.50689
Could you tell me please how to stop the program form changing the value of the section properties used in performing buckling analysis?!!
I am attaching the model file. you must input the values of the section in the Indian data table in the channel properties.
(Please visit the site to view this file)