4 ply - Wood Column?? (I NEED HELP FAST!!)

[JrStructuralEng]

I designed built up wood columns for a 4-storey condominimum based on the Canadian Wood Council - Wood Design Manual.

Here is the question: For a specific point load the design manual charts say I need a 4 ply B.U. column. Does this mean I need a 4ply column (i.e. 4 cripples) with a king stud? Or will 3 cripples and a king stud suffice??

I would only need 2 plys for bearing, but the code says I need a 4 ply based on length. Therefore I'm thinking 2 cripples and 2 king studs will work? Or 3 cripples and 1 king stud.

To complicate things I have to go on site and tell the contractor what's what in 15 hours. Please help!

 

[calculor1]

2 and 2 if bearing is ok

 

[dik]

Are you considering a moment in the column... maybe 4 members under the load so the 4 members are loaded concentrically more or less...

 

[OldPaperMaker]

JrStructuralEngr,
If the built-up column is in an exterior wall and it is acting as a Beam-Column (has a axial & lateral load) then all of the members should span from the bottom to the top plates.
Did you use the Column Stability Factor, Cp to calculate the allowable compressive stress & the Interaction Formula for combined compressive & bending?

 

[JrStructuralEng]

Okay, I just got 3 different answers to one question, hehe.

calculor: so I need the number of cripples I require for bearing?
dik: I didn't include any bending moment in the column in the direction we are both talking about for escentric loading. I was wondering about that, if you only put the load on 2 studs, it will put bending into the column won't it?

OldPaperMaker: some of these columns are in interior walls and others in exterior walls. I used the built up column design charts for the interior and beam-column charts for interior (based on height of column, loading, wind, etc.) You're talking about bending in the column in the direction i'm not concerned about. dik is more on track with my concerns I believe with his point above.

 

[dik]

a little bit, anyway <G>... If you can secure the beam? to the column to produce a 'fixed' type connection you can mitigate the moment somewhat...

Dik

 

[OldPaperMaker]

JrStructural Eng,
Sorry, but I can't give any more specific feedback about something that I really don't have much data about.
Also, please remember that free advise (from me) is generally worth exactly what you pay for it.
Good Luck!

 

[JrStructuralEng]

ok?

 

[RARWOOD]

The CWC WDM gives allowable axial load for the built up column. The center of the beam bearing should be at the column centerling. If it indicates you need four plys then you need a column with four plys nailed togther according to the publishe nailing schedule.

Think of it as solid column instead. In the past if you nailed four 2x6 togeher to make a built up column you determined the capacity based on a single 2x6 then multiplied by four. The CWC WDM gives a procedure to calculate a column capacity based on the nailing pattern.

The nails cause the built up column to be have differently than four single 2x6.

 

[msquared48]

If the built-up wood column is glued and nailed sufficiently, it should behave as a solid stick for the Kl/r factor. It just needs to be incrementally nailed at each layer to transfer the vertical loads and the shear due to bending evenly.

Mike McCann
McCann Engineering

 

[JrStructuralEng]

so if two of the sufficiently nailed plys are cripples and two are king studs, than it will still behave like a 4 ply column even though only 2 plys are bearing the weight? Is that what you mean RARSWC/mike?

 

[msquared48]

Yes - thru the nailing and gluing, the force can be transferred uniformly among all four.

Mike McCann
McCann Engineering