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Use of FEA
2

Use of FEA

Use of FEA

(OP)
How often do the professional engineers on this site use "real" FEA, meaning not the code checking portion of RISA or STAAD, but rather von mises stress contours, as opposed to hand calculations, for somewhat complex situations. Is it worth it for a new engineer to use some of these programs without having taken the theoretical FEA classes at university? I've found that's it's useful to validate my hand calcs when there is no clear code specification for my given project.

RE: Use of FEA

nknox....I use it fairly often. I don't use the code checks as final...that's for me to do. I use it for analysis of things that would take me a long time to do manually. I have checked the results of my software against hand calcs as required by my state law; however, I don't do that for every project. As a long time user of RISA 3D, I have confidence in the analysis, but still prefer to do code checks manually.

And yes...I do check von Mises and other stress variations as necessary; however, von Mises stress distributions in beams is not codified.....it is another tool for us to evaluate.

RE: Use of FEA

(OP)
Ron, as a long time Risa have you used "pate elements" and have you found the Von Mises stresses to be fairly accurate?

RE: Use of FEA

If you're asking this because you're in school and considering an FE class, then I'd highly recommend taking one if it's not terribly inconvenient. You'll know a lot more about what the program is doing, potential pitfalls, etc.

I use FE fairly frequently for stability and dynamic analysis. For example, I used a shell model with nonlinear analyses to predict the strength against a buckling mode like lateral-torsional buckling, but with unusual boundary conditions.

I do not tend to use FE for strength of plates or slabs in two-way bending. We don't usually go by first yield, and I don't want to do a material nonlinear analysis during design, so I'm more likely to use yield line analysis.

RE: Use of FEA

nknox....yes. I've checked it against Roark and others, and as best I can determine, it is reasonably accurate. Because of the non-homogeneity of materials and loading, it is difficult to analyze true accuracy; however, it seems to correspond nicely to other analysis programs for plate stresses. In addition to hand calcs, I check analysis programs by other programs as available.

RE: Use of FEA

(OP)
271828 I actually just graduated and started work, but I'm considering enrolling in an online masters and part of the reason is for a better knowledge of FE and the more specific facets of structural.

27128 What program are you using for these analyses?

RE: Use of FEA

SAP2000. Regarding nonlinear: I only use geometrically nonlinear analysis. I haven't tried material nonlinear. Thus, I don't get into von Mises, etc.

RE: Use of FEA

I use STAAD Pro for FEA all the time. I'm always having to consider plates with openings in them and hand solutions are cumbersome. I also have to use solid elements in some dynamic analysis I do.

If you can take an FEA class, it's probably worth it as you will (hopefully) learn some fundamentals. Hopefully the guy teaching it will have practiced and he will have useful advice.

RE: Use of FEA

On the one hand knowing the theory is nice. On the other hand it isn't essential. I initially ran a lab doing experimental modal analysis, generating the correlation data for FEA. As such when I started building FEA models mine were well correlated to real tests. I may not know the intricacies of the formulations, but I can spot a hokey FEA model at a thousand paces. Liberal use of RBE2s? Book him Danno.

Cheers

Greg Locock


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RE: Use of FEA

Using FEA programs is not the difficult part. Interpreting the results is. Knowing when a "hot spot" is really an issue needs a great deal of experience, and I have never felt comfortable basing designs on FEA models.

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