shearwall sheathing orientation- weak axis bending
shearwall sheathing orientation- weak axis bending
(OP)
I am looking at using 24" stud spacing on a project... for the first time.... (its energy related... hehehe)
So I have been looking into the out of plane capacity of the sheathing... to make sure thats not an issue.
Typical details I adopted, show the plywood orientation installed vertically. This is generally a more cost effective way to build. But, it also makes it difficult to determine the minimum sheathing thickness. All span ratings I have found, are assuming strong axis bending.
And so, I am re-inventing the wheel... and looking at a few characteristics of the typical details I adopted:
It is my understanding, that running the plywood vertically can eliminate the horizontal joints, and/or lends itself to staggering the horizontal joints. Both of these things, increase the stiffness in plane. (I wouldnt be surprised, if it also increased shear... although I found no difference in the code.) Can anyone point to a good document on this? (any document on the increase in shear capacity would be good too)
It is also my understanding that Structural 1 Grade has increased cross bending performance, and better racking. Can anyone point to a good document on this? Something with substance (numbers even)... for instance; how that increased racking resistance increases capacity... or, does the increased cross bending capacity, increase weak axis span capacity?
But primarily, I am looking for a way to determine weak axis capacity.... so I can be sure that a 24" spaced supports wont exceed the deflection limits or the stress limits....
meanwhile, Ill be checking the studs...
So I have been looking into the out of plane capacity of the sheathing... to make sure thats not an issue.
Typical details I adopted, show the plywood orientation installed vertically. This is generally a more cost effective way to build. But, it also makes it difficult to determine the minimum sheathing thickness. All span ratings I have found, are assuming strong axis bending.
And so, I am re-inventing the wheel... and looking at a few characteristics of the typical details I adopted:
It is my understanding, that running the plywood vertically can eliminate the horizontal joints, and/or lends itself to staggering the horizontal joints. Both of these things, increase the stiffness in plane. (I wouldnt be surprised, if it also increased shear... although I found no difference in the code.) Can anyone point to a good document on this? (any document on the increase in shear capacity would be good too)
It is also my understanding that Structural 1 Grade has increased cross bending performance, and better racking. Can anyone point to a good document on this? Something with substance (numbers even)... for instance; how that increased racking resistance increases capacity... or, does the increased cross bending capacity, increase weak axis span capacity?
But primarily, I am looking for a way to determine weak axis capacity.... so I can be sure that a 24" spaced supports wont exceed the deflection limits or the stress limits....
meanwhile, Ill be checking the studs...
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RE: shearwall sheathing orientation- weak axis bending
More in-depth sheathing properties, but careful, this stuff is confusing even for wood engineers: Engineered Wood Association Form No. D510E, Panel Design Specification 2020
Shear wall values are the same in both cases, panels vertical or panels horizontal: SDPWS 2015 table 4.3A
RE: shearwall sheathing orientation- weak axis bending
Are you aware of anything else that deals with deflection? I'm hoping for a table tat gives the minimum thickness for use with brittle finishes? Plaster finishes.. flexible finishes...?
Anyway
I know the code gives a value for either vertical or horizontal orientation. But just as an aside, I did come across some documentation, saying the vertical orientation, with staggered horizontal joints, was stiffer. And, the whole basis for diaphragm shear values is based on panel orientation..... so, I believe the staggered horizontal joint yields better shear values. This same document, had the table I need for out of plane deflection for brittle finishes.... but I cannot find it again. If I recall, for around 35psf wind, weak axis, 24" stud spacing... 5/8" plywood... but Im not sure I do recall correctly. Again, just as an aside.
Thanks.
RE: shearwall sheathing orientation- weak axis bending
RE: shearwall sheathing orientation- weak axis bending
I found a lot of good info. Unfortunately, nothing that addresses my specific set of circumstances directly. There is an APA table for weak axis bending for walls, for L/120, and another for stucco at L/360. Nothing in between. And again, 5/8" min thickness for weak axis, with stucco/plaster.
I design all my walls for deflections allowed for use with brittle finishes...... at a minimum. And who uses L/120? But, I didnt want to use 5/8" unless I had to...... so I kept looking.
Two things I did find:
1. Weyerhaeuser has engineered plywood, with strong axis in the 4ft direction... designed specifically for walls. Which I think is very cool.
2. I found a table in the code for roof ply, weak axis bending.
I used the code tables, and 1/2" appears to work.... but its close. So, I am thinking of also specifying the plywood with strength axis in the 4ft direction... I want to see how hard it is to get anyway... if its more expensive, if Struct 1 available, etc...... and this client will use Weyerhaeuser anyway.