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Notching W8x21 Top Flange

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XR250

XR250

Structural
Jan 30, 2013
5,763
I have a situation where we need to notch the top flange of a W8x21 flush beam for some immoveable water supply lines (1/2"ø). See attached. The notches will be within 32" of the support with a moment of about 9'-k at that point. The web will be packed out with wood on both sides to support 2x10 floor joists.
I have analyzed it assuming the notched portion is essentially a WT section (ignoring the un-notched flange). Using the section properties of a WT8x13 (which are a pretty nice fit - basically same web and flange), I get a bending stress of 27 ksi. If I assume I cannot get any local buckling of the tip of the tee due to the un-notched flange bracing it, then it should be compact and I can use an allowable bending stress of .66Fy. Does this approach sound reasonable? I checked deflection in my beam program by adding two short segments of WT section properties and it basically did not change. I am, also assuming I can ignore any twisting of the beam from the flange unbalance since it is framed flush.

Thanks
 
 http://files.engineering.com/getfile.aspx?folder=5ec50021-0c37-4014-b6a2-8476c3859e04&file=notch.png
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That should be fine as it sounds as though LTB is a non-issue. I'd combine both notches into a single cope and radius it so that you reduce stress concentrations.

I would have gone with analyzing the notched portion of the beam as a channel to improve the odds a bit. Six of one, half a dozen of the other..

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
 
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I can't believe that a competent plumber is not capable of moving a couple of 3/4 inch water lines. maybe get a half-a__sed handyman in to replace the plumber.

Richard A. Cornelius, P.E.
 
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Dick, I would assume the lines can't be moved because they are concealed in the wall above.

How big are the water lines? Can you just provide 1" holes to let them run their lines through?
 
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@dicksewerrat:
Of course they CAN be moved, but it would cause significant disturbance to the second story finishes which is not being renovated. Much cheaper to pay me to come up with a clever solution.

@Canpro - We could do the 1"Ø holes (the lines are 5/8" OD.), but the contractor would have to get them in exactly the right place - which may be asking alot.
 
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Hope you get enough for this. Tell the plumber to sleeve the pipes as they go by the flanges. A little water hammer will wear holes in the pipe.

Richard A. Cornelius, P.E.
 
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Sleeve the pipes, insulate them so there is no pipe-to-steel corrosion. (More likely with copper hot water pipe to steel flange, but ... we had pinhole leaks in the basement caused by corrosion where the water pipe touched a bracket.

But, if the pipes HAVE to run at that elevation (they can't be bent up a two inches?) then drill the WF through the web, run the pipes though the holes, then re-connect the pipe.
 
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@dicksewerrat
This is just one aspect of the renovation that I am involved in so I cant gouge them too much. Just curious how much would you charge not including the site visit.

@rakookpe
The beam is going under the bottom of the second story wall so they have to come thru the flange.
 
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Ok,
the wall on the second floor is in place and a bearing wall. Where do these water pipes come from? Are they in a headspace above the first floor ceiling? You can't put a couple posts, 6 inches apart down on the first floor. Where do the water lines go to? Fixtures on the 3rd floor?

Richard A. Cornelius, P.E.
 
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The wall being removed is on the first story. The lines feed the second story bathroom thru the bearing wall above. They extend out of the bottom of the bearing wall. The beam has to be installed tight to the bottom of the subfloor under the bearing wall. As such, there is interference from the lines.
 
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Waste line come out into the joist bay at a different location so it is OK.
There is no third floor.
Even if they could, it is still much cheaper to mess around with the engineering
 
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