bearing stiffeners on crane-runway beams

huangyhg

bearing stiffeners on crane-runway beams
hello all!
i am designing a crane runway beam and it seems like i will need bearing stiffeners to prevent web crippling/yielding. my question would be, how would i space these bearing stiffeners? the crane of course moves through the length of the beam, making web crippling/yielding a problem throughout the length. would i have to choose a beam with a thicker web as opposed to using bearing stiffeners? if not, i ask again, how do i determine a suitable spacing for these stiffeners? thanks!
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isnt the web buckling (crippling) resistance dependent on stiffener spacing? therefore they would need to be spaced as required and not continuous as you imply in your question.  
the equation that i am using w(n + 10t)fy do not have stiffener spacing in it.
i didn't mean the stiffeners have to be placed continuously.
it's very rare to need stiffeners along the length of a crane rail unless the loads are very significant.  have you considered the distribution of the load through the rail and the top flange?  presuming you have, and the loads still are too high, i would think (just a gut feeling) that it might be best to increase the web thickness rather than install spaced stiffeners along the length of the beam.  labour is nearly always the more expensive option, particularly when you are probably using the same (or more) material in your stiffeners.
there is a great publication from cisc called "crane supporting steel structures design guide" by r.a. maccrimmon.  it is an excellent resource, complete with design examples and model detailing.  i would encourage you to obtain a copy if you are going to be doing many crane rails.  available as a free download from
that seems to now be a link to a draft version of the second edition.  if you're uncomfortable using a draft let me know, i still have an electronic copy of the first edition (also freely available, when it was on that page).
cheers,
ys
b.eng (carleton)
working in new zealand, thinking of my snow covered home...
agree that bearing stiffners along the length isn't a good idea.  first, if you take the stiffners down to the bottom (tension) flange, you have fatigue concerns with the stiffner to plate weld.
second, the cost of adding all those stiffners is higher than the cost of a thicker web.

thanks all!
i will change the profile of the beam to one that has adequate web thickness.
to youngstructural:
i'm looking at the first design example right now and one thing that is standing out is that the book calculates "mi" and also the equation that they used for "mu" is quite different than s16. are these equations from aisc? thanks!
it is page 91 of the draft of the second version.
clansman:
this is indeed from aisc; please see "design method", p. 35 for an explanation of the term mi... essentially it is mu.
hope that helps!
regards,
ys
b.eng (carleton)
working in new zealand, thinking of my snow covered home...
pardon me, mi is a limited mu...
i should really read my previews more carefully!
sorry for any possible confusion...
regards,
ys
b.eng (carleton)
working in new zealand, thinking of my snow covered home...
thanks a ton, friend! this book from cisc is really helpful! i'm set.