Building a stud wall under a beam

[ELREng]

I am in a dialog with a contractor who wants to install a stud wall under the full length of a beam (5.5x13.5 GLB spanning 15'-8"). The stud wall lands over a girder in the crawl space below. His opinion is that nothing in the crawl space is affected because the GLB beam above the new stud wall is there doing what it would do if the stud wall was not there. My concern is that the new stud wall prevents the GLB from deflecting and therefore "short-circuits" the picking up of load as it would if the wall below was not there. My opinion is that the new studwall will be a bearing wall and therefore the girder below in the crawl space needs to be looked at. Any opinions?

 

[KootK]

I agree. Unless there's a gap or something that gives, I'd expect the load to transfer through the wall to the girder below. Perhaps the issue could be solved to the satisfaction of all parties by modifying the detailing at the top of the wall.

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.

 

[XR250]

My guess is that it is a self limiting condition depending on how far above code minimums the GLB was designed.

 

[DETstru]

You are correct, if the wall touches the underside of the beam it will take load.

You could make it a non load bearing wall and provide a double top plate with a deflection track. I think there was a thread about this not long ago.
Here's an article:

http://www.woodworks.org/experttip/...partition-walls-underside-floor-roof-framing/

Regardless, you'd have to check the crawl space girder to make sure it can handle the weight of the wall (which it probably will).

 

[kipfoot]

My opinion is that the new studwall will be a bearing wall and therefore the girder below in the crawl space needs to be looked at

Agreed. How the system behaves under load is dependent on the relative stiffness of the GLB (which I'm assuming is glue-laminated beam) and the beam below. I don't think that you necessarily have to leave a gap over the wall or reinforce the lower beam for the full load, but you have to understand how the beams interact under the shared load.

 

[msquared48]

All this is assuming that the columns/studs can transmit the vertical load without failing or crushing the plates, which will affect the amount of load transferred, if any.

Mike McCann, PE, SE (WA)

 

[XR250]

Add some addition studs under the GLB that bear down on the piers. That will effectively bypass the girder in the crawlspace altogether.

 

[hokie66]

Both beams will carry load. You can do the calculations, but the beams will themselves decide how much each will take. Probably much ado about nothing, as the load path will vary as the beams deflect.

 

[azcats]

I'd use some Simpson STC or DTC clips with a gap and forget about it. It's $10 in clips and I'd spend more than that analyzing two beams.

 

[AaronMcD]

Assuming the stud wall can take the load. If the girder below is weaker/lighter load, chances are it is also more flexible. Which beam deflects more without the stud wall? Yeah, if the girder deflects less, it will pick up more load, but it won't deflect more than the Glulam. Just distribute loads based on relative stiffness and check the girder. Or just detail the top of the wall with a vertical gap.