WF beam bending question

I have a W12x40 in pure bending that has a 3" hole notched on one side of the top (compression) flange. It is 2" from edge on center. How can I calculate the bending stress for this? Will there be a concentration factor at the hole? I haven't been able to find any references on this. thanks,

ER

 

[csd72]

No easy way to calculate this exactly.

Best conservative way is to treat it as if this area has been taken out top and bottom.

Then calculate the reduced I using

Ireduced = I - 2Ad^2
where A=area of hole (in cross section),
d = distance from neutral axis.

Then calculate an S value from the new I.

Look up roarks for stress concentration factors.

 

[271828]

Wow, back up a minute, LOL.

What's the lateral bracing condition for this beam? If it's adequately braced, you might get off pretty easy by calculating a new Zx and/or maybe applying the 13th Ed. Section F13. Not sure F13 applies completely, but it's worth a look.

 

It's pinned to a 1" jack bolt on each end.

csd72,
Do you think it would be a better approximation to assume the top flange is a flat plate w/ hole and use the appropriate concentration factor for ten/comp?

 

[frv]

I'm with 271828.

I think what you need to do is apply section F13.

 

[msquared48]

As a fix, you might consider two pieces of flat bar of the same total area as the hole welded to the flange longitudinally. This should replace the section you have lost.

Mike McCann
McCann Engineering

 

[csd72]

licensetochill,

yes, thats what I had in mind, but you first need to get the unconcentrated stress..

But my comments assume that the beam has continuous lateral restraint, if not then you need to also check buckling as others have noted above.