Crushing of WSP 2

[Flotsam7018]

Continuation of this old thread: https://www.eng-tips.com/threads/crushing-of-plywood-really.371840/page-2#posts

I've been running into this issue a lot lately and having to block out the subfloor at columns. APA D510 provides a perpendicular to grain capacity of 360 psi for a 0.04" deformation. Any additional thoughts on this matter 10 years later?

 

[ChorasDen]

What precisely is the question that you are asking here? Fcperp is a unique attribute of wood that has values assigned based on a proportional limit approach. This differs from the approach used for other properties (fcparallel, Fb, Fv, etc). Be aware that OSB does not typically have uniform properties through the cross section. Binding and performance of the center fibers may not be identical to the face fibers, due to the method of pressing the product.

SDPWS et. al. make it very clear not to overdrive the nails when framing engineered shear walls and diaphragms using wood structural panels. I would consider fcperp within this same concept, in that we don't want to affect panel properties by causing excessive local damage by exceeding Fcperp, but then again, that's just one engineers opinion.... I also understand the frustration of the low value of 360psi, but such is the nature of a commodity product, and the way APA defines design values for this product line.

 

[Flotsam7018]

I was looking for some updated takes or insight on considering crushing of the sheathing as a failure mode at concentrated loads. Are folks out there looking at this and if so where’s the cutoff for you?

I generally only check crushing of the plates, but when I start using engineered lumber columns, especially over two stories, I will check this and often have to block out the sheathing for the column to pass through. I called Huber a few years back on this as I thought there’s no way Advantech only has 360 psi crushing strength, but was told they don’t have any test data to prove otherwise.

 

[Flotsam7018]

@XR250 @KootK you guys were both on this original thread, any input here? Still just checking plates only and carrying on with life?

 

[XR250]

I use the bottom plate to spread the load out slightly - maybe 45 deg?. Other than that, I just try to make the column wider or the wall thicker.

 

[Flotsam7018]

Let's say we can't make the columns bigger and we have mitigated crushing of the plate by using SCL or some other means, so load spread will not resolve the issue.

 

[XR250]

In that case, I remove the subfloor and support directly to the supporting structure. You could also put a PSL column sideways at the base between a couple of studs to prevent rolling to spread out the load. Never tried this but have thought about it.

 

[KootK]

@XR250 @KootK you guys were both on this original thread, any input here? Still just checking plates only and carrying on with life?

Doh... the moment that I've been fearing has arrived. Despite being the OP of the other thread, I was kind of hoping to skate under the radar on this as I've already 'fessed up to several marginally criminal business practices this month. Wishful thinking I suppose.

Yup, I've been ignoring the plywood crushing wholesale ever since that other thread. No problems to report thus far.

Somewhat in keeping with our other active discussion, one of the things that I like best about sheathing is the kick ass job that it does of laterally bracing the ends of my posts. So, to notch the sheathing for the sake of the crushing business kind of feels like robbing Peter to pay Paul to me.

Yeah, I get that there are other possible paths for doing that same job but none is as direct or as natural. I'd hate to have a post kick out on one of my projects and then have to explain the sheathing notching. "You did what at the bottom of this big post now?!?".

 

[XR250]

If we are being honest, I typically ignore it as well but do honor the plate crushing numbers.

 

[Flotsam7018]

Appreciate the honesty.

So, to notch the sheathing for the sake of the crushing business kind of feels like robbing Peter to pay Paul to me.

No argument from me here on this one. Completely agree.

However - there does have to be a line and of course that line is fuzzy. I was hoping someone had some new insight that would confirm my suspicion of the capacity being extremely conservative and therefore certainly not worthy of neutering the typical column stability and having to detail some way around that which has a decent chance of being done incorrectly.

 

[jerseyshore]

Doh... the moment that I've been fearing has arrived. Despite being the OP of the other thread, I was kind of hoping to skate under the radar on this as I've already 'fessed up to several marginally criminal business practices this month. Wishful thinking I suppose.