LVL Crushing 1

[XR250]

Was in a crawlspace today of a 3 story, wood framed condo. Was there investigating continued complaints of sheetrock cracks. Based on my laser measurements, pier settlement seems to be the biggest offender. However, I also observed many instances of the 3-ply, 18" LVL beams in the crawlspace showing signs of crushing over their SYP wood blocks (see attached). I measured about 1/4" of crushing with a computed existing load reaction of about 7k or 200 PSI perp. to grain. The SYP appears unfazed by the load. WTF? I though the LVL design values were about 750 psi for perp. to grain loading.
The LVL brand is "Weldwood" which appears to have been bought out years ago. My guess is no help from the new owner.

The building is 10 years old and pretty consistently lightly loaded with retirees (trussed roof clear spans the crawlspace). As such, I doubt the load changes much. Do you think the crushing has done all it is going to do?

 

[manstrom]

I would have put money on the plates crushing before the LVLs. It's hard to tell from the pictures. Maybe the environment had something to do with the glue losing capacity. Don't know.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[msquared48]

Are you sure the LVL is crushing? It looks like the SPF 2X block to me...

Mike McCann, PE, SE (WA)

 

[SWEG]

If the glue loses capacity then you'd most likely see a direct reduction in compression perp. to grain.

A picture taken from slightly above the plate looking at the LVL would help determine that the plate isn't spreading/crushing at the end as well.

Any thoughts on redistribution of floor loading caused by pier settlement? Further, floor loading at this one reaction point is actually more than you think, especially if the LVL's are continuous over supports allowing redistribution of load due to settlement of piers at surrounding areas.

Just a thought...

Virginia PE, SE

 

[XR250]

I am pretty sure it is the LVL. See how the grain is displaced. Here is another pic. Love how the girder tie down was misplaced and just bent flat to reach its target.

 

[XR250]

@PJW.
It is happening at most of the piers. The LVL's are cont, but about 4 spans worth so the reaction is not that much more than simple span.
The owners want to just patch up the sheetrock at this point and visually monitor it.

 

[SWEG]

The 2nd picture is definitely helpful. You can see the grain deformation in the 2nd.

Are moisture and temperature something to consider in the NDS load factors? It is a crawl space, so moisture is probably higher (probably not temperature, most likely cooler).

It's probably best to just visually monitor settlement and crushing at the plate.

Virginia PE, SE

 

[Signious]

Is it a built up beam? If so are all of the plys flush at the bottom?

I have seen similar crushing where one of the plys was a bit thicker than it's counterparts, so the load was directly on that one ply until it crushed down flush with the rest and gave full bearing.

 

[XR250]

@Signious - it looks like the plys are flush.

I have had so many problems throughout the years of sagging LVL's that the manufacturer's blame on "putting them up wet" so now I oversize them considerably (even more than I always have).
Now I have to contend with crushing at the bearings - jeez!

 

[mike20793]

Are there floor joists that frame into the sides of the LVL, or does the floor framing bear on the LVL? I wonder if it's a load distribution through the built up beam. If they aren't connected together properly, one side can take more load than the other, depending on the spans. I've read about this happening, but I've never seen anything like it before. Are all the plies crushing?

 

[XR250]

They are all dropped beams so the load should be pretty evenly distributed

 

[mike20793]

I'm guessing the spans are pretty similar, so that would rule out the uneven loading. That's very unnerving to see it crushed like that under such a relatively light load. Is the LVL crushing on both sides of the blocks?

 

[msquared48]

If the pier was settling, why is the metal strap to the right in the second picture buckled? Looks more like the pier has heaved, particularly considering the fact that the crack in the footing to the right appears to be wider at the top than further down.

Can't explain why the LVL would fail over the SPF though, unless there was water/moisture damage. Is the crawl space vented properly? Any standing water in the crawlspace?

Mike McCann, PE, SE (WA)

 

[XR250]

@mike20793 - some are, some are not. Might be that the pier cap is not level.
@M^2 - The strap is not buckled. It was installed in the wrong location and just beat with a hammer until it met the LVL.

 

[msquared48]

Is the crawl space vented properly? Any standing water in the crawlspace?

Mike McCann, PE, SE (WA)

 

[XR250]

The crawlspace did not seem overly wet and did not see any mold growing on the trusses. I did not bring my moisture meter with me, however.
Might be worth another trip out there.

 

[msquared48]

Just because it is not now does not mean so in the past. Any recent floods in the area?

Mike McCann, PE, SE (WA)

 

[XR250]

Went back to the site with my moisture meter. Readings on all beams were between 15 and 17%. Over 16% is not considered a dry service condition. I imagine in the summer, the readings would be a lot higher. It is a large crawlspace with very little venting and an incomplete vapor barrier. My guess is the elevated moisture has some responsibility for the crushing of the LVL's.

 

[lsmfse]

What is the metal strap? It almost looks like a post base. Is there a concentrated load above that was intended to transfer into the post base? It appears there is a large gap between the post base and LVL's?

 

[XR250]

It appears to be a poorly located tie-down strap that is performing zero function