STAAD Advanced buckling analysis engine 1

[sinu21]

Hi Friends

i am trying to do a buckling analysis of a complex model and i thought o do a verification model for better understanting. I made a plate of
Length=5000mm
Width = 3000mm
thickness of 10mm
Load = 10N/mm2

and i gave a fixed support all around, But the values i get are not the same as the manual calullation that i can do using a spread sheet.I am sure some one has gone through this before and got a solution.
I will put down the results and the staad files along with this for help.

Results.
When loded laterally.
manual = 33.876N/mm2
Staad ratio = 34.482 that means 340N/mm2

When loaded longitudinaly
Manual = 11.16 N/mm2
Staad ratio = 33.414 that means 330 N/mm2

Can you plz help me, give me some guidelies how to chose which mode and where i have gone wrong in analysing ...

Thanks ...

 

[dozer]

I took a look at your model. Here are some comments:
1) You generally want to look at the first mode of buckling.
2) You can't fix all four edges like you did and expect any meaningful results.
3) Let one side slide and load that side. Fix the opposite side but don't load that side.
4) You say the load is 10 N/mm^2. That's what you told STAAD to do but I'm not sure that's really what you meant to do. Your applied load if you just look at one direction is 1500 kN according to STAAD. That gives you a stress of 1500kN/(5000mm x 10mm) = 30 N/mm^2. Read up on the way STAAD applies pressure loads to elements to be sure you are doing what you intend.

I modified your file and ran it and got a buckling factor of 0.336, which means the critical buckling stress is 10.08 N/mm^2. I'm not sure I did exactly what you intended but the mode shape made sense to me. I don't have access to the closed form solution but the result seems reasonable. I've attached my mods. See if it's what you want. If not, maybe at least it will help you understand what you did wrong.

Buckling analysis is not for the uninitiated. Be sure you really understand this stuff before you tackle a complicated problem.

 

[dozer]

Sinu21, it's been 2 months since I replied. I spent a fair amount of time trying to help you but there has been no response. It would be nice to know that my effort wasn't wasted.