Wood Design Kh factor in CSA Standard O86
Wood Design Kh factor in CSA Standard O86
(OP)
In CSA Standard O86-01, Table 5.4.4, the "System Factor" Kh is given for "compression parallel to the grain" as 1.10 for Case 1, and 1.00 for Case 2 built-up beams. There is no listing for built-up columns. I am checkimg a built-up wind-column in the exterior wall of a cottage. It takes s small axial load due to roof dead load and snow, and a wind load which has a much greater effect than the axial load.
Questions:
a) Would I be correct to use Kh=1.00 for the resisting momnet calculation, and 1.10 for the compression strength of the column?
b) Why have they listed "built-up beams" but not listed "built-up columns" in the table?
c) Why have they listed built-up beams for CAse 2, but not for case 1?
d) Do other Standards have a similar table, and if so, what have they listed for Kh?
e) Has anyone used this table for VSL wood (i.e wood studs made up of vertical laminations), or is it not applicable?
I can attach a photographed copy of the table if that would help (I don't have a scanner at home).
Questions:
a) Would I be correct to use Kh=1.00 for the resisting momnet calculation, and 1.10 for the compression strength of the column?
b) Why have they listed "built-up beams" but not listed "built-up columns" in the table?
c) Why have they listed built-up beams for CAse 2, but not for case 1?
d) Do other Standards have a similar table, and if so, what have they listed for Kh?
e) Has anyone used this table for VSL wood (i.e wood studs made up of vertical laminations), or is it not applicable?
I can attach a photographed copy of the table if that would help (I don't have a scanner at home).






RE: Wood Design Kh factor in CSA Standard O86
b) Because a built-up wind column is the same as a built-up beam with additional compressive stress. That's why the Kh factor goes up for bending and down for axial load. The compression from axial load helps the moment resistance to a point.
c) When do you ever have identical built-up beams spaced at max 2 feet on centre?
d) don't know, I'm sure they must have something similar to account for load sharing across parallel members.
e) In canada vertically laminated posts are used but they're typically designed by the truss guys because they're laminated using truss plates. I'm sure they use portions of this standard but I'm not sure what else would apply to the design of them.
Oh and the most current edition of the CSA is O86-09.
RE: Wood Design Kh factor in CSA Standard O86
Thanks for getting back so quickly .
I am aware that the most current edition is 09, but I am working from home yesterday and today and do not have the latest edition at home. I have the following follow-up questions:
a) ok
b) the Kh for columns is 1.10 and for built-up beams is 1.00. So Kh goes up for columns and down for built-up beams...it seems to be the opposite of what you say...or am I misunderstanding something?
c) If you interpret "members" to mean beams, then I see your point. But if you interpret members to mean the plies of a built-up beam (such a 4-2x6"s), then Case 1 would apply. No?
e) I was referring to something different. I meant something like "Versalam". My feeling is that O86 is not meant to be used for such proprietary products, because I am having difficulty understand how to select and apply some of the factors.
RE: Wood Design Kh factor in CSA Standard O86
c) Don't apply Kh to individual plies, apply it to your section (The total of all the plies). If you fasten them correctly they act as a single unit and that is how the strength of it should be calculated.
e) I don't see why you couldn't use the system factors for that type of material however as I said previously, when calculating the resistances by hand I generally just use a Kh=1.0 for both bending and compression unless the members are classified as case 1. All of my TrusJoist (Weyerhauser) stuff says they design according to the CSA O86 so I would think they would apply.
RE: Wood Design Kh factor in CSA Standard O86
RE: Wood Design Kh factor in CSA Standard O86
RE: Wood Design Kh factor in CSA Standard O86
RE: Wood Design Kh factor in CSA Standard O86
RE: Wood Design Kh factor in CSA Standard O86