FE analysis of steel connection
FE analysis of steel connection
(OP)
I am doing FEA for a complicated connection in a steel framed building. I am in search of a code or reference that would provide me with an allowable stress or strength of the steel. It seems that the AISC manual does not apply as I do not have simple bending, tension or compression forces. I want to have an appropreiate factor of safety at the same time not being over comservative, as it has already been designed by my client and is used numerous times. Have you done a FEA of steel before, what did you uses as an allowable stress and what was your basis? Any help or direction would be greatly appreciated.
Thank You,
Thank You,





RE: FE analysis of steel connection
RE: FE analysis of steel connection
Look back in AISC-ASD at the section dealing with bearing in bolt holes, and you'll find that the allowable bearing stress can exceed the yield stress in that situation. But that doesn't mean the part has "failed". I suspect that if you start looking at fillet welds in great detail with FEA, you'll find very high stresses there at times, too.
With the ASD, I'd probably try to show that the attached beams would fail in bending (or compression) before my connection failed. (I think you'll find some of the safety factors in the commentary.)
RE: FE analysis of steel connection
RE: FE analysis of steel connection
Regards,

Qshake
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RE: FE analysis of steel connection
Firstly I apply factored loads to an elastic model, and compare with the yield stress. If there are a few places over the yield stress, I consider a nonlinear run with plastic material properties and look at the plastic strain. In Europe hand designs for tubular connections are based on CIDECT rules and its unlikely that you can match these capacities (which were based on test results) without accepting a degree of plasticity.
RE: FE analysis of steel connection
RE: FE analysis of steel connection
There's something to be said for connection designs that absolutely require FEA - they may need design mods that make them easier to treat with manual calcs, thereby increasing not only the margin of safety, but also your margin of confidence!
Thats my 2 cents ($CAN)
tg
RE: FE analysis of steel connection
It sounds like you have a problem where you are evlauating bi-planar stresses (different than bi-axial). I have a similar problem where I have strong-axis bending + axial compression + flange prying on a steel pile. I am trying to evaluate if my flange is locally overstressed due to the bi-planar stresses and shearing stresses. I do not believe that the AISC Manual of Steel Construction addresses this behavior.
I am considering comparing the principal plane stresses OR von Mises stress to ......(here's where I need help or a reference).....and the maximum shearing stress to .....(again, need help here). I am working w/ service-level loads. Do you have any references you could suggest I review that provide recommended allowable normal and shearing stresses?.....Would you recommend a different analysis approach?
Thanks in advance for your thoughts.
RE: FE analysis of steel connection
Have fun!
RE: FE analysis of steel connection
As a designer in the USA, with some experience with FEA and steel connection design, I wouldn't use FEA for this, PERIOD. Unless you have a tremendous amount of expertise in FEA, you will get A result and not have a clue whether it's reasonable. It might even look reasonable but be garbage.
Years ago, I did some of this for part of my thesis and was astounded at the difference in results from choosing different types of shell or solid elements. Much of this had to do with advanced parameters that most designers know nothing (or at least nowhere near enough) about, such as the type of integration, etc. I could change a seemingly benign parameter and get answers 30% different, either higher or low.
I also don't know what kind of program you're using, but I would want something like ansys or abaqus for serious modeling. I would not use whatever generic element that the typical structural packages throw in there. Who knows what it'll do.
Just my $0.06.
DBD