Finite Elements
Finite Elements
(OP)
How many of you are using finite element analysis on a regular basis? I have never really trusted finite elements and have always used the code equations whenever possible and tried to be conservative when the codes don't quite fit the application. But I think some engineers try to use finite elements as much as they can.
I have heard some other engineers say that FEA is a method for the future of the profession. I don't know...I am just looking for any opinions on FEA in general.
I have heard some other engineers say that FEA is a method for the future of the profession. I don't know...I am just looking for any opinions on FEA in general.






RE: Finite Elements
I currently use a program (based on the stiffness matrix method) to do the stuctural analysis part of my design and then use Mathematica to do the code checking, not that I am recommending this approach here. I feel comfortable using computer programs for analysis but haven't been able to warm up to the code checking parts yet. You could also use general purpose FEA programs to do the same as long as you use line elements in your model.
When someone mentions FEA I think about models made from plates or solid elements. Some of these programs can solve for buckling but I have no experience with how well they work and accuracy that can be expected. The codes call for ASD or LRFD however, so I wonder what use the more complex solutions would be.
Just my 2 cents.
Regards,
-Mike
RE: Finite Elements
I would think about using FEA in a situation where you have an element that is out of the ordinary (like a curved steel plate under a non-uniform load) where FEA can give you a tool to look into the behavior. I am just unsure about using it in more routine applications and how you can compare the results to what the codes stipulate, particularly in buckling situations.
RE: Finite Elements
RE: Finite Elements
If I were solving the same sort of problem often, I would think that would be a good application for FE. But most often I see folks use FE because they don't understand the problem well enough to do it by hand.
RE: Finite Elements
If a design code method is applicable then it's wiser to use that. In a lot of cases, however, the code doesn't apply or a situation or failure occurs that is outside the scope of the code. The use of hand caluclations can make many more assumptions than you would with finite elements and hence the errors can be greater. I don't know why haynewp says that finite elements is the way of the future as I've been using them for 25 years. Unfortunatly the design codes haven't kept up with techinology advances and still use 'Noddy' calculations with huge safety (or don't know) factors, just in case.
corus
RE: Finite Elements
I first used FEA about twenty years ago and quickly became impressed with the sophistication of the analysis and the complexity I could build into the model. I used line elements only, no plates or solids, and did the code checking with my own program outside of the FEA. I used three dimensional models not really because I had to, but simply to do the bookkeeping involved with orthogonal loads. Not being a highly skilled mathematician I am happy to use software for this part of the design process.
I am working with different programs today but still use the same process. Structural analysis with commercial software and code checking with Mathematica. The next step for me would probably be integrated code checking, but beyond that who knows.
-Mike
RE: Finite Elements
This is just one example that can be modeled in less than 5 minutes with today's software.
RE: Finite Elements
Sure there are some people do not understand FEA and believe the software will do the work for them. Part of the problem lies in the understanding of FEA. I spent 4 years solving matrices and learning the many different methods of structural analysis. Good fun at the time, but of limited use in any of the modern day design offices I have worked in. Building character and rigour was probably the intended end product. Part of the problem is that it requires effort and time understand structural analysis. These same people would have struggled with stiffness or moment redistribution methods in the days when these were cutting edge techniques. The profession, as any other, will always have lightweights.
I currently design both PT and RC slabs. I have done PT calculations by hand and enjoyed doing it. There is no doubt you get a better feel for what you are designing, although this is probably because you have sent an hour looking at it. PT design is not a quick process. Add to the equation the client who changes his mind like the weather and FEA is the only option. In my opinion FEA is not the future, it is the now. It is time the codes and universities we work to and attend recognise this fact.
RE: Finite Elements
As far as where FE fits into our engineering toolbox, obviously it's here to stay until something better comes along, but that good engineering judgement and common sense demand that FE not be the only tool in that toolbox, and that hand stress calculations, handbooks such as Bruhn, etc. will forever remain essential tools in that toolbox.
RE: Finite Elements
RE: Finite Elements
FE on the other hand, does not readily indicate mistakes once you have a connected model. It also doesn't help an engineer understand where the loads are going nor does it show him what is driving the problem. You can make mistakes in FE and learn very little from fixing the problem, which is unlike hand solutions.
Observations related to the high pressure of the office environment and irregular geometries are well taken. I'm not sure how an engineer gets real experience today. It is my belief that folks come out of engineering school with understanding or they don't and little analysis will be learned after graduation. Codes can be learned on the job, and plan preparation, specification writing, contracts, ... can all be learned in the office. But substantial new analysis is probably not going to happen.
I've seen a lot of work submitted to me for checking or review to scare the heck out of me. I wonder how someone can get paid to do a job with no capability? I don't think they are so cavilier to not care about the potential consequences to others and themselves, so I have to believe they don't know any better. But, that goes for hand calcs and computer calcs.
RE: Finite Elements
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