huangyhg

stiffness
does anyone know of a site where i can get a reference for the stiffness (k) values of simple structures - propped cantilevers, single bay fixed fixed frames, double bay, double storey and the like.
i'm trying to analyse simple problems but they all start with needing to know the stiffness value and deriving it from first principles takes time and isn't the objective of the excercise.
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what kind of exercise is it?
"formulas for stress and strain" has some data for various frame types.
it's just structural dynamics, but it's coming up in plastic analysis.
is "formulas for stress and strain" on this site or do i google it or what?
roark's formulas for stress and strain
since you noted that the exercise is for structural dynamics you should note that the stiffness matrix will be dependent on idealized system and not the conventional stiffness mattrix that one would use for structural analysis.
all of the items you mention with the exception of the double story building can be modeled as single degree of freedom systems. the two story frame will require a two degree of freedom system.
the time it takes to derive one of these stiffness matrices is minutes compared to the aggregate sturctural stiffness matrix.
many examples are available in so many texts on structural dynamics such as timoshenko, clough and penzien, craig, and chopra, borg and bolton and so many others. most have direct examples.
regards,
qshake
eng-tips forums:real solutions for real problems really quick.
bandraoi: here are some propped
bandraoi: i just noticed yab at the above propped cantilever link contains an extra parenthesis, so the yab formula should instead be:
yab = (fbx^2)[(3l^2 - b^2)(x) + 3l(b^2 - l^2)]/(12eil^3)

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