Cutting out web of W-shape Beam

[coachdave7]

Designed a beam for a house to help support the wood floor trusses. A W12x35 runs the length of the house in two sections, with one end of each section connecting to the foundation and the other end connecting to the flange of a W12x22. Now, after installation, he is going through with the HVAC installation. He wants to run it through the web of the W12x22 by cutting out the middle 8" of the web for 12" on one side of the connection and 16" on the other side of the connection. The W12x22 spans 4'-7" (reduced from the 9'-0" from the original design). The W12x35 connects at the midspan of the W12x35.

Now, I determined the moment couple based on the new centroid locations of the reduced T-sections. I determined the allowable compression and shear in the reduced T-section. And according to my analysis, everything checks out that it would be OK to make this modification.

Am I missing something??? because I feel awfully hesitant to give him the green light.

Has anyone else done something like this???

 

[hokie66]

So you have a hole 8" deep x 28" long in the web of a W12x22? And a W12x35 beam is supported on the 2" deep tee section that is left? If that is the case, think again, as that tee is not going to carry the load in bending.

 

[SteelPE]

I would feel hesitant as well. Check out AISC DG 2 Web Openings. Here you should find a majority of the answers you need.

 

[dik]

A W12x35 loading a W12x22 will put the W12x22 in a high shear, likely. The long hole will require a high flexural resistance in the top and bottom portions of the W12x22... not likely possible. W12x22's are flimsy. The duct will have to be re-routed and go under or additional supports will have to be introduced.

Dik

 

[BAretired]

A W12x35 runs the length of the house in two sections, with one end of each section connecting to the foundation and the other end connecting to [highlight #FCE94F]the flange of[/highlight] a W12x22. Is the web of the W12x22 horizontal?

Now, after installation, he is going through with the HVAC installation. He wants to run it through the web of the W12x22 by cutting out the middle 8" of the web for 12" on one side of the connection and 16" on the other side of the connection. The W12x22 spans 4'-7" (reduced from the 9'-0" from the original design). The W12x35 connects at the midspan of the W12x35 (should this read W12x22?).

BA

 

[dhengr]

Maybe some day they will teach engineers to do sketches and drawings, so they can express their design ideas in a way that allows others to understand what they are talking about. Until then, since we can’t see what you are looking at, 20 questions or 20 guesses is such a fun game. In the mean time why don’t you just eliminate all the steel beams which you haven’t defined very well, and since the HVAC contractor/designer came to the party late, just have them furnish structural duct work which will serve both purposes, since they want almost all the structural space.

 

[paddingtongreen]

Condensing the opinions above, we can't visualize the arrangement from your description, it will take a sketch to cover the sort of complication you indicate.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[msquared48]

Sounds like this was not planned out very well, with the OP entering the fray after the fact. Recipie for a disaster...

To the OP: If you have been retained to solve this, do not be try to be Mr. Nice Guy

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[hokie66]

I took the OP's description to mean that the W12x35 is either bearing on the top flange or hung from the bottom flange of the W12x22, right at the location where "he" wants to butcher the W12x22 to for ductwork. If that is correct, it won't work.

 

[paddingtongreen]

I agree hokie, that is the best fit interpretation but there are others that arepossible.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[RareBugTX]

My take on this is a matter of priorities. What is more important? A safe structure or a convenient air flow in an HVAC system. The hole size sound unacceptable.....without doing any numbers and if by chance the contractor came with a print-out showing that it is allowable by AISC, I wouldn't sign on it.

 

[BAretired]

I think hokie's interpretation is probably correct, i.e. the web of the W12x22 is vertical and the two W12x35 beams bear on top of the top flange.

It appears that the OP has not considered secondary bending on the two T-sections. Cutting of the web as described cannot be permitted.

BA

 

[MiketheEngineer]

So where is the architect in this mess??

 

[BAretired]

It's a house. There likely is no architect..possibly a drafting service.

BA

 

[paddingtongreen]

Never mind the architect, where is the OP?

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[coachdave7]

Thanks everyone for the input, or at least asking for clarifications. I was actually pointed in the right direction by one of the initial responders pointing me to AISC's Design Guide 2. That text cleared up all of my questions. Sorry for the lack of drawing... next time it will have one. Thanks again.