huangyhg

direct stiffness method
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 assume that the grad level class will include some advanced topics like buckling, small displacement 2nd order analysis, cables, etc. there's great value in understanding how the programs do these things. people mis-use these feature very frequently when they don't understand the underlying assumptions and methods.
this is an interesting question.
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.
i did a fair bit of fem theory and associated calcs at uni and would rate the exercise as not worth the time and effort required. you can gain as much understanding by reading some general fem documentation and interrogating your software manual (and support staff) for answers and advice for the essential items listed by 271828. i would rate knowing how your specific software program works much higher than a detailed understanding of the history of fem and the methods employed by each program.
is there a reputable university anywhere that would let somebody get a ms without taking a course in the dsm (matrix structural analysis)?! i'm familiar with several universities and i am completely confident that none of them would allow someone to squeak by without it.
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.
completely agree with 271828 (your locker combination?)
i wouldn't be so fast to dismiss the benefit of a matrix / fem class. i took one in grad school and it was one of my best and favorite classes. i use sap2000 and etabs every day and i feel much more comfortable using those programs now that i know what processes they use internally. i feel that i have an advantage over my co-workers who haven't taken an fea class when using the programs. the math isn't any fun, but to gain a different and in my opinion useful perspective on the behavior of elements, frames and structures is very beneficial.
rb, it's an inside joke, and a fairly poor one at that. my little girl is adorable and her name starts with "e" so i started calling her "little e" which of course became e. engtips' stupid username limitations wouldn't let me have a decimal!
i had a class on matrix structural analysis at the undergrad level - and my degree is an et degree....... go figure!
i think a class in this is essential before someone should be turned loose with any stiffness program. i hope you will learn the sign convention used by these programs, the difference between an element that includes shear or does not include shear deformations, the fact that it takes special coding to accommodate buckling and plastic analysis if you need it and other "under the hood" checks that should be understood.
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.
why would any university force you to take a dsm (matrix structural analysis) class for your ms (i am referring to mechanical or aero engineering here. i don't know what civil engineering ms students take)? many universities are quite flexible with their class options--you might have to take 2 'structural mechanics' classes (in addition to math and fluids and thermal), but the list of structural mechanics is often quite long, with classes in finite elements, fracture mechanics, elasticity, plasticity, and continuum mechanics. now it may be a great idea to take dsm or msa classes as you have suggested, (given the ubiquity of these methods in current engineering practice), but why force that class down someone's throat (more or less)? people take many different career paths upon graduation, and many may not see the need to understand dsm or msa theory so thoroughly.

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借用达朗贝尔的名言：前进吧，你会得到信心!
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