Opinion on IDEA statica - connection design software 3

[waren1991]

Hello Gentlemen,
I have recently started using the connection design software IDEA statica which works based on Finite element analysis.The results I get seems realistic & I have submitted those calculation to EOR in some cases...it was approved as well...but still wondering whether all Engineers will accept the finite element analysis based calculations for connection design...I have attached a sample report for your review & comments.

FYI, I use Idea statica software only in scenario where a standard connection design format is not available or a the connection is quite complex to design...Otherwise I perfer manual calculations.

 

[CANPRO]

It is a tool just like any other software or calculator. I'm a regular user and I think it is a great tool. However, if not used properly it can produce incorrect results that look nice on paper. I find sometimes this type of software can give people a false sense of security. You need to pay particular attention to how you define connection eccentricity - this is something that is critical regardless of you method of calculation or analysis.

I see in your report that you aren't using loads in equilibrium. I strongly suggest that you always check that box and make sure the loads in the joint balance out. This will force you to think more about the eccentricity in the connection.

My general opinion on design software is that if you can't draw by hand what you expect the deflected/deformed shape to be then you shouldn't be using the software. This definitely applies to IDEA Statica.

 

[dig1]

waren1991,

Great question. We perform FEA regularly but mainly for pressure vessels using ASME Section VIII, Div. 2, Part 5. While my comments are skewed in that direction we also do a fair amount of structural steel work mainly for non-building structures.

I also prefer manual calculations but sometimes FEA is "better" provided it is done reasonably.

If I was submitted these calculations for review without knowing the software (which I do not but have wanted to look into) I would have the following comments/questions (this is random order as they came to me):
1. What is the element type and order.
2. Type of analysis (linear-elastic, non-linear)
3. Boundary conditions, restraints, including any symmetry
4. Need to see the mesh.
5. Was a convergence analysis performed. What if the max strain had been 4.9% and was "ok" but with a finer mesh or a different element type it was 6.9%?
6. What is the stress equivalent (page 5 of pdf); I'm assuming vonMises.
7. Are stresses average or nodal?
8. Brief description of why/where load location was placed.
9. How are the bolts modeled in the holes?
10. If slip-critical is initial bolt load included and if so how?
11. Validation of software on a simple connection that can be done by hand.
12. Buckling was not performed but the "why" it was not performed needs to be mentioned someplace even if it is a sentence that it does not apply for a specific reason(s).

Some of the questions may not apply or may be trivial. If the connection designer/engineer can address them then they are likely understanding what is happening and someone is not randomly entering data. The last sentence applies to all software and just not FEA.

Hopefully some of what I wrote makes sense.

 

[dig1]

Canpro,

You responding while I was writing. Great points.

 

[271828]

My general opinion on design software is that if you can't draw by hand what you expect the deflected/deformed shape to be then you shouldn't be using the software. This definitely applies to IDEA Statica.

That can't be emphasized enough.

You should have a pretty good idea what the answers should be. It should be in the ballpark of what you'd get from a manual approximation.

FEA for connection design purposes is pretty scary. The plots, marketing figures, etc. are very impressive. That might give the idea that the calcs are super advanced and accurate -- trust them even if they're a lot different from your manual calcs.

There's a guy in one of the other forums that likes to say that every engineering student needs to try and match FEA and experimental results to provide a proper perspective on how bad the predictions often are. I think that's 100% correct. (Not talking about IDEA Statica in particular.)

 

[SWComposites]

Agree, devil is in the details. dig1 has a good list above.

How are the fastener connections modelled?
There are stress peaks shown - what is done with those results? How do you know those stress peaks are accurate or converged?

 

[Italo01]

The creator of the software (Frantisek Wald) published a book called "Benchmark Cases for advance design of structural steel connections" where the methodology is presented and some simple cases are done to comparison with experimental results. I suggest it for anyone interested in using Idea Statica.