LVL Crushing
LVL Crushing
(OP)
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?
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?






RE: LVL Crushing
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
RE: LVL Crushing
Mike McCann, PE, SE (WA)
RE: LVL Crushing
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
RE: LVL Crushing
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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.
RE: LVL Crushing
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
RE: LVL Crushing
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.
RE: LVL Crushing
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!
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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)
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@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.
RE: LVL Crushing
Mike McCann, PE, SE (WA)
RE: LVL Crushing
Might be worth another trip out there.
RE: LVL Crushing
Mike McCann, PE, SE (WA)
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When forte came out with the bearing check included I know it was a shock for some people how often bearing was the controlling failure mode.
Is it possible that the original designer didn't check?
In my experience deep narrow lvls don't do well with bearing
RE: LVL Crushing
But the horizontal 2x10 is in a" safe" (flat) condition, isn't it?
But, the two seem to have squished "safely" in that they are not delaminating nor distorting across the web: Only the lower "flange" of the LVL is distorted - and that distortion is on the bottom of the lower flange. The upper flange appears un-distorted, doesn't it?
What do the other posts in the basement look like?
RE: LVL Crushing
RE: LVL Crushing
Does this post only pick up a small portion of the main floor?
7k seems low for standard residential loading, at 60PSF total that's just over 100 sqft. A 3 ply 18" lvl should be more than capable of that.
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I based the numbers on the current loads - which are about 20 psf total (not the design loads). The girders do not span very far.
You use 60 for residential? I use 40 live and 10 dead. Even if the actual dead is higher, I know I the floor will never see 40 psf anyhow.
RE: LVL Crushing
The 2X member on which the LVL bears is not treated, and there is no building paper between the concrete aid the 2X plate to prevent moisture migration. The LVL is seeing moisture from the concrete through the 2X plate.
The LVL specs in the #TJ-9020 Specifier's Guide definitely say that they are not for use in a "wet" environment, however they do not allude as to what they consider "wet". Probably have to call Weyerhaeuser on that. The Fc Perp is 750 psi and cannot be increased for duration of loading, so a higher than allowed load should not be the problem here.
I would recommend jacking up the LVL to relieve the load to the 2X plate, pulling the plate out, installing 2 layers of 90# building paper over the concrete, and reinstalling the 2X plate. May have to temporarily disconnect the strap too. I would also recommend better ventilation in the crawlspace, even if has to be forced. This will not remove the deformation, but prevent more from occurring.
Mike McCann, PE, SE (WA)
RE: LVL Crushing
and even at 1/4" of crushing that's still likely a tolerable amount if it doesn't progress further. I would be any damage seen above is 95% due to pier settlement and 5% others factors (I still wouldn't attribute the whole 5% to lvl crushing)
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How do you know it is not treated - i bet it is.
Also, no one has every put anything between the 2x and the pier in any structure I have been in - just not a common practice around here.
I have already recommended a sealed crawlspace system.
@Jayrod - "But it is entirely possible it saw something closer to design loading at some point and the crushing occured"
I find this unlikely, but certainly possible. My money is on the moisture
RE: LVL Crushing
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Thanks boo1. I try to please...
Mike McCann, PE, SE (WA)
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"Also, no one has every put anything between the 2x and the pier in any structure I have been in - just not a common practice around here."
This really irks me. It is a really easily accomplished task, and everyone knows why it is important. Saying no one does it is a really piss poor excuse not to require it yourself, it is a code item where I am, and I suspect a code item anywhere - wood in contact with soil-contacting concrete is P.treated or 6mil poly gets put down.
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I fully agree...
Mike McCann, PE, SE (WA)
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Mike - Our PT wood is pine and it does not have indentations. Once it ages, you cannot tell the difference between PT and non-PT.
@Signious - my comment assumed that a PT sill plate was used - which it typical in all of our construction.
FWIW, I have been doing this since 1991 and have literally been in 250 crawlspaces per year since then (probably significantly more than anyone on this forum). Most of the homes I look at are 40 to 80 years old and have their pine or oak beams bearing directly on masonry piers. Few have any rot. The ones that do typically have a widespread problem as well. As such, the whole "don't let non-PT wood touch masonry" argument does not hold too much water with me (no pun intended) even though I adhere to that rule. Even in this particular case, some of the LVL beams were bearing directly on masonry. Their moisture readings were no different than any other beams and were actually in the best condition.
RE: LVL Crushing
Mike McCann, PE, SE (WA)
RE: LVL Crushing
Could wicked moisture be seasonal or one time, wetting the LVL leading to the localized crushing?
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I hear you about the wet PT lumber. I think if that was the case, the LVL's would have slid off s the stuff can be like ice when wet
BTW, it is central NC
RE: LVL Crushing