moment of inertia for built-up beams
question:
if i have an i-beam and a c-channel stacked and welded as one, to find the "i" of the "built-up" member can i just add the two "i" values together, or is there some other method of finding the combined "i."
thanks
steve mackie, product/applications engineer
apical conveyor systems, inc.
tavistock, ontario
see
this can be found in many text or exam review manuals.
one more thing, c channel should be oriented horizontally, thus use the i value for the weak axis. iy.
also, isnt there a table of section properties for i beam and a challel in the aisc steel manual? unless it is a bizarre combination, you should be able to find the values you need from the steel manual.
thanks guys, i don't have an aisc steel manual, i have a few books from lincoln and my text books, but never really did that much structure so i just needed a little quick refresher and fast. there are a lot of smart people here that re
packie,
your question about structures (acutally its about section properties - aka deformable bodies) makes me wonder what you are using this built up seciton for? finding the capacity of an i section with an attached channel is more than just finding the i. could you tell us what this is used for? thanks
sure, the channel is a track for a roller to run in, and it is sitting on top of the i-beam. the s6x17.25 is in the usual position and the 7x12.25 channel is in the "i" position on top. there are two of these parallel about 48" apart and the wheels of a horizontal scrap conveyor run inside the channel.
steve mackie, product/applications engineer
apical conveyor systems, inc.
tavistock, ontario
hi packie81,
you don't mention how the channel is attached to the i beam. horizontal shear connectors at intervals are required to utilize the composite section for bending.
regards
vod
my mistake, you mentioned it is welded as one.
vod
voyageofdiscovery, i think your point is very well made. two pieces being welded as one, i am guessing, is a continuous fillet welds along each side. my question is: is that necessary?
only connection you need is to be able to resist the amount of shear flow between the two pieces so they act compositely. like voyageofdiscovery sugggested, intermittent welds or even bolting at certain spacing may suffice.
hrm, i find some of these answers going much deeper than i expected.
whyun: no, we wouldn't do a continuous weld over the 40', probably wouldn't be much more than a 1-12 1/4" fillet.
steve mackie, product/applications engineer
apical conveyor systems, inc.
tavistock, ontario
2009-09-10, 02:59 PM
moment of inertia for built-up beams
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