Direct Stiffness Method
Direct Stiffness Method
(OP)
This is a question for those who have learned the direct stiffness method and how the structural analysis programs work. Did you gain any real practical knowledge from it? I am curious because I am taking a graduate level analysis class on this stuff in the fall and I have a hard time seeing how much it will truly help me.
I have no ambitions to write my own FEM code. It seems like it is just trivial knowledge otherwise. Yes, I understand it is nice to know how the program assembles the stiffness matrices and solves for the unknowns, but I don't really understand how this will make me a better structural modeler. I sure there is some value to it, but I just don't see any offhand. I'd appreciate feedback of any kind. Thanks.
I have no ambitions to write my own FEM code. It seems like it is just trivial knowledge otherwise. Yes, I understand it is nice to know how the program assembles the stiffness matrices and solves for the unknowns, but I don't really understand how this will make me a better structural modeler. I sure there is some value to it, but I just don't see any offhand. I'd appreciate feedback of any kind. Thanks.






RE: Direct Stiffness Method
RE: Direct Stiffness Method
I did the direct stiffness method at school and the Professor spent a lot of time on it. To be absolutely honest I found it wasn't really worth the time we spent on it. Understanding of the meaning of bending moment, shear force, and second order analysis, end moments, etc is probably more important than the method. Having good structural sense such as approximate solutions to problems is more important so that a check can be done on the output files.
You dont have to know how to set up a stiffness matrix to be able to use a sophisticated structural analysis program.
RE: Direct Stiffness Method
RE: Direct Stiffness Method
You guys are typing about being a "technician," or "button pusher," not a MS-level structural engineer. That's a road that shouldn't be gone down.
Sorry--that's just the way I see it.
RE: Direct Stiffness Method
RE: Direct Stiffness Method
RE: Direct Stiffness Method
RE: Direct Stiffness Method
RE: Direct Stiffness Method
I believe an engineer could go his entire career without working out a single integral. But I'd never want to work with one that did.
RE: Direct Stiffness Method
RE: Direct Stiffness Method
I believe there is a vast difference between being a button pusher and being a button programmer. I agree that is essential to know the in's and out's of your program and it's concepts.
I may be speaking from my own experiences with an impractical FEM course but I believe that time spent grinding through heavy calcs and theory is not going create a better engineer than equivalent time spent researching and understanding the practical application of the theory developed by others.
With the vastness of knowledge, training and limited time available to most of our profession, a focused and practical approach has to be taken to training.
I admit it would be nice to know everything though.
RE: Direct Stiffness Method
Given your little inside joke concerning your nom-de-EngTips, you should read Richard Feynman's delightful autobiographical book of anecdotes "Surely You're Joking, Mr. Feynman". In particular the anecdote titled "Safecracker Meets Safecracker".
RE: Direct Stiffness Method
I have an MS, I took both matrix structural analysis and FEA (DSM & Structural Dynamics were the only required courses for the structural MS, the rest are electives). I work for a company that has two divisions, standard structural design (what I'm in) and high end analysis (mainly done on FE software).
I am currently working on this project which requires both design/detailing and high end analysis. Part of my job as the designer is to do a hand analysis and design, which is then checked in FE and more refined results are given.
The other part of my job on this project is to check the FE results. This would have been IMPOSSIBLE for me to check if I did not know things about ill-conditioning, stiffness matrices, integration points, element types, mesh sizes, local FE effects and numerous other topics, all of which I learned in my grad classes. Now, we are all human... and I did find quite a few discrepancies and was able to intelligently discuss with the engineer who was doing the FEA and get them resolved. If I didn't have this experience they would have had to bring on another guy to check the FE stuff, or I may not have gotten on this project all together.
Not to mention you should never use a program in which you don't know enough about how it's arriving at the results, it's very poor practice in my opinion.
RE: Direct Stiffness Method
RE: Direct Stiffness Method
There are inevitably going to be situations during the modeling process which require hand verification, experience and a 'gut feel' for confirmation. I personally pepper the programmer with questions every time I have even a glimmer of an inconsistency, anomaly or unexpected result. I have found that this as a resource, has been far more beneficial to my development than the tedious, demanding and mostly forgotten FEM course I undertook. It is obvious that different courses will offer different levels of practical material – speaking from my experience, I gained little – and certainly not practical tips on 'how' to generate a model or what to what watch out for.
271828 have your skills been honed by your graduate level FEM class or later software and design courses, experience and gut feel? Again, all education has merit but with time being such a precious commodity I believe any training regime should be directed to the most beneficial and specific skills required.
RE: Direct Stiffness Method
RE: Direct Stiffness Method
As full disclosure, I'm not in design any longer. I had a DSM class and a FEA class during my MS program and I think they helped. I've since taken additional coursework, including 2 other DSM classes. A LOT of this, for me, falls into the "Dang, I wish I knew that when I was using these programs!!" category. Things like virtual work optimization, buckling, response history, different types of nonlinearities, etc.
I admit that this subject is debatable. IMO only, at least one class (DSM or FEA) should be taken by anybody with a MS. OTOH, a curriculum only has a certain number of classes and there might be something else that is more valuable.
Whether programming should be a part of the class is also debatable. I *think* that could be dropped without hurting the class. That being typed, in my last two DSM classes, we had to program everything, all the way up to cables, buckling, etc., and I do believe that increased my depth by quite a bit.