mp2333
Student
- Feb 3, 2022
- 3
Hi everyone,
I am currently working on the buckling of concrete shells. More precisely, I am trying to analyze already built shells, which means that I know what are the actual geometric imperfections.
I know that the typical procedure for a buckling analysis is to start with a linear eigenvalue analysis, and then use the shape of the first eigenmode for a nonlinear buckling analysis.
If my understanding is correct, the use of the first eigenmode as imperfection in the nonlinear analysis is a way to use a "worst-case" shape and obtain conservative results. However, in my case, I know what are the actual imperfections that occurred in the production process, and they are included in my 3D model.
I tried to perform a linear eigenvalue analysis and a nonlinear (geometric only, material is linear) analysis on this "imperfect" model, and surprisingly the critical buckling load is higher for the nonlinear analysis.
I did the same for the design model (without imperfections), and the same result happen (even though both critical loads are higher than for the imperfect model).
Therefore, I have three questions:
1/ Does it actually make sense to perform an eigenvalue buckling analysis for a model with geometric imperfections given that I know what the real imperfections are? From what I found online, they seem to be only included in the nonlinear analyses.
2/ How would you interpret the nonlinear critical buckling load being higher than the eigenvalue buckling analysis ? I read that it happens sometimes but still it seems suspicious.
3/ What do you think is the critical buckling load I should consider for the rest of my work? The seemingly conservative eigenvalue buckling load or the higher nonlinear buckling load?
Thanks in advance!
I am currently working on the buckling of concrete shells. More precisely, I am trying to analyze already built shells, which means that I know what are the actual geometric imperfections.
I know that the typical procedure for a buckling analysis is to start with a linear eigenvalue analysis, and then use the shape of the first eigenmode for a nonlinear buckling analysis.
If my understanding is correct, the use of the first eigenmode as imperfection in the nonlinear analysis is a way to use a "worst-case" shape and obtain conservative results. However, in my case, I know what are the actual imperfections that occurred in the production process, and they are included in my 3D model.
I tried to perform a linear eigenvalue analysis and a nonlinear (geometric only, material is linear) analysis on this "imperfect" model, and surprisingly the critical buckling load is higher for the nonlinear analysis.
I did the same for the design model (without imperfections), and the same result happen (even though both critical loads are higher than for the imperfect model).
Therefore, I have three questions:
1/ Does it actually make sense to perform an eigenvalue buckling analysis for a model with geometric imperfections given that I know what the real imperfections are? From what I found online, they seem to be only included in the nonlinear analyses.
2/ How would you interpret the nonlinear critical buckling load being higher than the eigenvalue buckling analysis ? I read that it happens sometimes but still it seems suspicious.
3/ What do you think is the critical buckling load I should consider for the rest of my work? The seemingly conservative eigenvalue buckling load or the higher nonlinear buckling load?
Thanks in advance!
