Single LVL beam

[XR250]

Got a situation where I have joists breaking on a 2x4 stud wall. For many reasons, we cannot easily install a girder under the wall even though crawlspace piers exist at 10 ft. spacing.
The contractor has proposed fastening a single 1 3/4x16" LVL to the face of the stud wall tight to the bottom of the joists. He would support the LVL above each pier with a vertical 9 1/4" LVL that would have (4) studs behind it to brace it against weak axis bucking. The LVL columns would be blocked solid to the pier caps. The numbers work out on the LVL beams and columns as far as bending, deflection, bearing etc. My gut says another failure mode is the LVL beam and column just wanting to peel away from the stud wall. In reality, I doubt this is an issue.
FWIW, the load on each column is about 3.4 k.
Any thoughts or concerns?
If I have to, I can design everything as conventional 3 1/2" thick but the owner does not want to lose anymore square footage.
Thanks.

 

[SLTA]

sketch please?

Please remember: we're not all guys!

 

[XR250]

here you go....

 

[JAE]

Is part of the 2x4 stud wall eliminated over a span of some kind and thus the need for the LVL?

Why the LVL?

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[XR250]

We cannot install a girder under the wall due to extensive mechanicals. The LVL is there to support the loads of the joists and transfer that load into the vertical LVL columns which can be supported on the piers in the crawlspace. The 2x4 wall would not be load bearing due to the LVL and would not require a girder below.

 

[SlideRuleEra]

The concept looks good, but there are issues with the Contractor's proposed columns. Refer to Trus Joist TJ-9000 Specifier's Guide, July 2016:

LVLs are not rated for use as columns.
LSLs and PSLs are rated for use as column use, but not the 1 3/4" thickness. Their minimum thickness as a column is 3 1/2".

Using a "too thin", unrated LVL as a column does not sit well with me... even though it would probably work just fine.

Perhaps 2 x 10 lumber, with 1/4" plywood spacers to get the 1 3/4" thickness, could be considered for the columns.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[BAretired]

The vertical 9 1/4" LVL cannot peel away if (a) the screws are adequate in tensile capacity to prevent it buckling about its weak axis and (b) the four studs over each pier are laterally tied to the floor above and below.

BA

 

[XR250]

Using a "too thin", unrated LVL as a column does not sit well with me... even though it would probably work just fine.

I agree, but should work better than a 2x10.
My guess is that it simply has not been tested in that orientation as why would anyone use it that way
I think I am going to run with it and BA's comments make me feel better about it.

 

[KootK]

My gut says another failure mode is the LVL beam and column just wanting to peel away from the stud wall.

I think that you're on to something here. Without the fastening to the wall, you'd have a pin-pin joint where the new header meets the new post. To assess that stability issue, I might assume a reasonable kink at that joint and evaluate the demand on the nearby fasteners in that light. I'm sure it wouldn't take much to get the job done. Because the demand on the fasteners would be tensile, I like screws much better than nails here. And you've already picked that up in your detailing, probably for similar reasons.

My guess is that it simply has not been tested in that orientation as why would anyone use it that way bigsmile

1) With a "column" of this proportion, I'd definitely consider some strong axis load eccentricity. That will create a need for LTB bracing which would need to be supplied by those 4-2X working in torsion. Not a big deal, I'm sure.

2) I suspect that the 3.5" min column dimension is about preventing extreme column slenderness. In your case, from a buckling perspective, the radius of gyration for the columns would rightfully include the effect of those 4-2X's as well. Another reason to, perhaps, feel okay about drifting off reservation a bit.

If it is the case that you'll just be furring out the wall for the 1.75" anyway, the solution below may have merit. It would eliminate the columns and eliminate any stability concerns altogether. I'd probably lean towards using a couple of stacked 2x12. That would simplify the furring.

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]

Kootk,

Can't use your solution as there are doorways to contend with. The LVL columns have to be in specific locations to align with the piers in the crawlspace. There is no girder below as shown in your detail (the joists run thru and bear on another girder - they are in bad shape but the owner does not want to deal with them. Hence getting the new load down to new piers)
On a side note, having the LVL beam tight against the upper joists lets the load transfer directly without having to go into the wall and then into the beam through fastener shear.
Also, you will rarely see TJI's on my jobs as I hate them

 

[HouseBoy]

I think the solution you (OP) show looks good.
I'd specify something to anchor the wall studs to the plates above and below and for the plates to the floor framing, especially around the column locations but even over the length of the wall too for the general stability of things. The 4 2x4 studs fastened to the "flat" LVL column seem appropriate to provide stability.

Curious why the 9 1/4" column though. Seems wider that I would expect and much wider that the 4 studs that are holding it stable. How did you establish that width was needed? At 3.4k I'd expect 1 3/4" x 5 1/2" or so would be adequate. Maybe would go to 7 1/4" but not sure what 9 1/4" was chosen here.

 

[XR250]

Curious why the 9 1/4" column though. Seems wider that I would expect and much wider that the 4 studs that are holding it stable. How did you establish that width was needed? At 3.4k I'd expect 1 3/4" x 5 1/2" or so would be adequate. Maybe would go to 7 1/4" but not sure what 9 1/4" was chosen here.

The 9 1/4" width is easy as that is the smallest they sell around here and no ripping is required. It also keeps the bearing stress on the subfloor down to about 225 psi - which minimized crushing deflection.

 

[BadgerPE]

How about this alternate (see sketch-2 pages)? Add an LVL to the other side and solid block between LVL members. Provide through bolts as needed. Add a cripple along the (4) ply 2x4 "column". Forces are transferred concentrically then and you don't lose any floor space. Might not work with your HVAC though.

 

[XR250]

@BadgerPE -
Thanks for the sketch. That still leaves a bump in the wall on both sides - which is undesireable aesthetically. The one sided solution lends itself to easily furring out the entire wall.