Finite Element Analysis 1

[structural-eng]

I'm looking for recommendation regarding structural finite element analysis software for designing simple steel structures for an electrical substation. We have a client (an electrical engineer) that we have been designing substation structures and foundations for that is looking to bid on a new project and the spec for the project requires "Structural Finite Element Method (FEM) analysis should be used as a base method for design. Hand calculations of components may be used only under written approval." Our company has been around for 40+ years and we have never gotten into finite element design. The work that we do is not complicated enough to warrant it. These substations are very basic structures (cantilevered columns, pinned and simple fixed end connections, etc) and the member sizes used are driven by desired geometry and deflection limits and rarely by strength requirements. The only area where we believe we could likely reduce the structure size from our current designs is the base plates which have large holes for galvanizing and are on leveling nuts which requires very thick plates when using a traditional design approach. Any recommendations would be appreciated.

 

[klaus.]

well there are 1000+ FE element programs around the world ......

we use this one [URL unfurl="true"]https://www.dlubal.com/en[/url]

 

[human909]

FEA is a great tool and also a great escape from dealing with the complications of dealing with the principles and codes of structural engineering. I say this as somebody guilty of the of the latter.

I believe your assessment is correct. FEA is likely not needed and is likely to be inferior and a waste of time compared to your conventional methods of design. If I was in your position I would start by asking the question of your client, why is this requirement in this project. No harm in still bidding for the project regardless but qualify your bid as necessary. FEA is no panacea, it gets quite complicated and potentially less conservative when it comes to buckling and other aspects.


Though to answer your question. For steel FEA I use Inventor Nastran. It is quite powerful and relatively easy to use if you can model appropriately with Inventor. The free trial helps too.

 

[structural-eng]

Thanks human909. I'll look into Inventor Nastran more. We don't currently use Inventor in our office but the electrical engineer we work for uses Inventor to model all the structural steel so perhaps that will speed things up some. We will definitely try to qualify the bid to exclude the FEA as I think it will be an exercise in busy work but if this is the directions projects are going we will probably start looking into what we can do to meet these unnecessary requirements.

 

[JAE]

My graduate school professor once barked at a student who asked a question about FEA vs. "stick beam" analysis.
The prof stated something to the effect that "Two-node, six degree of freedom "stick" members are finite element analyses as well...they are just two node instead of more."

Perhaps your "FEA" is a two node stick-member approach using hand methods!

 

[rb1957]

There should be many "shops" (companies) near you who could do the FEA of your foundation.

The issue would be do you see this being the future direction of analysis, or a one off ? If one off, then out-source; if future direction then develop the ability internally (understanding that it'll take time and money to build this.

I understand your contract requires FEA (with hand calcs as a bad 2nd) … odd, most FEA are supported by hand calcs (to demonstrate that the FEA is realistic and reliable).

another day in paradise, or is paradise one day closer ?

 

[WARose]

Programs like RISA and STAAD are industry standards (for steel design).

 

[StrucPEng]

I would second Klaus's suggestion. I have used Dlubal software and it is very easy to pick up and can do simple and complex structures. RSTAB might be best in terms of cost and requirements to analyse steel frames vs. cost of the full RFEM program. Sounds like your office is pretty proficient with pen and paper design so maybe just a basic FEA program to be able to check the box of using the software for contract purposes.

 

[mchen96]

For a one-off (if you're just looking to check a requirement and will double check with hand-calcs), you could look into Code-Aster + Salome for windows. It's not particularly easy to use nor is it very intuitive and has a tough learning curve, but it is trustworthy (if it's good enough for nuclear reactors, it's good enough for me) and (more importantly for some) free.

I've used SAP2000 and it gets the job done, although the auto-mesher for shells & plates is not very impressive. That being said, it is relatively easy to use and well documented.

I've heard good things about RISA, although I believe they only offer a subscription license nowadays.

 

[r13]

There are pros and cons for design using FEM, or computer programs, exclusively, let's not get into it. I think modern engineering office do need to have programs to facilitate the design process, the question is what fits the nature of your business, and experience level within your office. I would start internally to get inputs from the ultimate end users - your fellow engineers.

 

[Liam Nesson]

I understand a client dictating the format or file type of a deliverable but an electrical engineer dictating the structural design method seems unusual. This might be a good time to educate the client, industry standard practice vs more costly / complex method. I notice some other disciplines rely heavily on FEA, its possible this has influenced the client. That is unless i have missed the boat and everybody does their structural engineering in FEA.

We use Staad for FEA, when its required, but I am sure there are better programs.

 

[KootK]

The written approval thing certainly has the potential to slow things down.

1) what is the nature of the upstream client who was actually the specifying party for that requirement? I'm just trying to gauge their probable level of sophistication.

2) is there also a requirement to submit your FEM models as one of your deliverables? I'm wondering if the upstream client is striving for improved documentation for the sake of future modifications etc, similar to BIM.

If it's possible to query the upstream client on their reasoning with this. I would attempt that given that there are only two root possibilities:

3) they don't understand what they are asking for, don't really need it, and require educating OR;

4) you don't understand what they are really asking for and require educating.

From the perspective of successful project management, it's always a bit dangerous to take on an assignment with an incomplete understanding of what will constitute project success from the client's perspective.

 

[dik]

Any time I've been involved with a project where the client/customer requires detailed verification... I always thank him, in writing, for his review of the work... just to share the liability... and with one project I received a terse reply that they weren't reviewing the work and I replied that their requirements went far beyond the normal industry standard... only did one project for that client...


Dik

 

[dreber]

Everyone here is providing well thought out contentextual answers.

I vote RISA.

Cheers

=========================
David Reber

http://www.kadent-structures.com

 

[rb1957]

isn't this "just" a contract deliverable … nothing to do with checking the engineer's work, or having the analysis fit the problem.

the contract says "produce an FEA of the structure", possibly 'cause that's what the client's business chart has, possibly the client is a 2nd tier supplier to a 1st tier manufacturer who has mandated "FEA for all structures" ?

having to do an FEA as a one-off is a lot of work (for people unfamiliar, unpractised, in it). Subcontracting it to an "FEA shop" is expedient. The next business decision is "is this to be an ongoing thing ? do we want to have this analysis capability in-house ?"

another day in paradise, or is paradise one day closer ?

 

[drawoh]

... We have a client (an electrical engineer) that we have been designing substation structures and foundations for that is looking to bid on a new project and the spec for the project requires "Structural Finite Element Method (FEM) analysis should be used as a base method for design. Hand calculations of components may be used only under written approval."

I am not a structural engineer or even a professional engineer for that matter. I have on occasion been asked to do safety calculations on stuff I have designed. I studied my structures looking for failure points, which turned out mostly to be bolted connections, and the flanges around my screws. I solved these by hand. Using FEA on these features was beyond my ability and beyond the capabilities of my software. I did use the FEA solid modelling on some details. It is easy to take a bolted structure and model it in SolidWorks as a single piece of material. This should provide a fairly accurate model of stiffness, but there is no way I would trust the stress analysis.

I have had discussions about FEA with people, not professional engineers, who regarded it as a magic box that knows the answers to their questions. FEA output can be colourful and pretty, and look good as part of somebody's PowerPoint presentation. This does not make it accurate.

Why is an electrical engineer, or his client, telling structural engineers how to do structural analysis? This is just like adding tap drill sizes to drawing and insulting machinists, except you are not just insulting someone. I had to submit my calculations to the customer's engineers. As professional engineers, you are supposed to analyse the problem, and use the appropriate analysis techniques and tools.

--
JHG

 

[Tomfh]

JAE makes a good point. Simpler 2D stick based programs are finite element programs too.

It’d be worth assessing what the client is demanding before rushing out to purchase a fancy rainbow generator.

 

[RamKrishna Das]

Dear sir

You can go for staad which is widely used FEM analysis software.
Beside that it has the lowest cost in terms of license. There are
other software which are available in the market like- SAP, RISA , Ansis etc..

 

[GregLocock]

"Structural Finite Element Method (FEM) analysis should be used as a base method for design. Hand calculations of components may be used only under written approval."

You don't have to show your working. Design it by hand then model it in FEM. If there are any discrepancies then your internal 4am in the morning computer will kick in and force you to work out why. Banning the checking of FEA models is quite ridiculous, all FEA should be checked by other means.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[ldeem]

Maybe there is a trend in power industry to specify certain work flows. I am currently reviewing a spec on a power plant project where the owner (power plant) is mandating all fab shop drawings to be from a 3D program (I engineer/design/detail myself so no issue for me). I though it strange the owner would mandate a certain work flow to a consultant. Deliverables do not include a 3D model.