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Eccentric Load on Flange of W-Shape
2

Eccentric Load on Flange of W-Shape

Eccentric Load on Flange of W-Shape

(OP)
I am looking for guidance on the proper way to analyze a beam where the load is supported by the flange, in this case, a hollowcore concrete panel "nested" inside the web, bearing directly on the flange.  I recognize the load is eccentric, and will try to make the beam twist.  It also seems to me that the flange will act like an unsupported element, subject to bending stress.  Am I missing something?

thanks in advance.

the rattler

RE: Eccentric Load on Flange of W-Shape

I ran into a similar problem this week - I ended up using
an FEA analysis to solve the problem. Do you have acess to
FEA software? I thought about treating the flange of the beam as a cantilevered beam (with flange connection at the web being restrained)to see what kind of stresses I would get?
One problem I see with that is the flange is wide compared to its length so bending theory is probably out the door.

RE: Eccentric Load on Flange of W-Shape

(OP)
Thanks for your reply.  It turns out this is no longer needed in this project, as the design has changed otherwise and this "nesting" is no longer needed.  Now the problem is just an intellectual one.  I would think FEA is a pretty good way, I just thought this condition might be more widespread than it apparently is.

Thanks anyway for your help and interest, I really rely on Eng-Tips, it's been terrific for me.

RE: Eccentric Load on Flange of W-Shape

I wondered how a contractor might erect that hollow core slab as you described it- I can't see how he'd get it up between those flanges.  

As for the intellectual question, that looks a little like the loading you get from crane wheels on the bottom flange of a monorail.  Those are point loads on the flange, usually out at the tip.  

For those, I've used an old printout from CMAA-74 to calculate the bending on the cantilever flange, this in turn must be combined with the bending stresses (major axis bending) on the gross section and combined using the Hencke-Von Mises interaction.  For the hollow core slab, it may be uniform loading and the CMAA 74 doesn't directly apply.  Maybe Timoshenko or Roarke could get you what you need.  

regards,


chichcuk

RE: Eccentric Load on Flange of W-Shape

I've also come accross this problem before - I adopted a rectangular hollow section for the beam with a bottom flange plate to pick up the pc floor.  The beam can be designed for the effects of bending and resultant torsion.

(Being a UK based engineer, I'm not sure what profile a 'W' section is !!)

Of course this problem only exisits at edge beams because internal beams have pc floors both sides and therfore the resultant of the loads acts through the centroid of the section assuming spans both sides are equal.

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