Engineered Lumber For Tension Member?

[StructuralEd]

Is it appropriate to use engineered wood, parallel strand lumber, as a tension member?
There are a couple of manufacturers' softwares, one of which doesn't allow negative inputs and another that has a limit but without reason.
Are there issues with using the material in that manner?
If it's allowed, would a conventional lumber approach be in order?
I would presume that it matters which face the connections are made into, but don't know of potential shortcomings of the materials.

 

[EngineeringEric]

Are we talking about uplifts for lateral? or long term tension like a hanger?

 

[StructuralEd]

Application is for wind uplift on a column.

But since you mention it I wondered about truss fabrication for future reference.

 

[EngineeringEric]

I know Simpson Hold Downs and post bases publish uplift values for their attachments. See LCB/CB and HDB. They publish values for installing into the wide face, but also have literature if installing into the other face.

Truss Fabrication would involve permanent tension in the bottom chord... I do not know why that would be a problem since the bottom fibers of an LVL are always in tension. I am guessing this is something that you would have to have verified by GP or Boise Cascade, give them a cal, they may like the exercise.

 

[Triangled]

i don't see any fundamental problem with utilizing engineered wood lumber as a tension member, BUT, each manufacturer is a little different and each product is a little different and brand names change and interchange enough so everyone gets confused. SO, I'd recommend you study the manufacturer's data carefully, especially the footnotes under their tabled values and specify exactly what products you accept. The face you connect to/through does make a difference for some products in some applications, kind of like the difference between nailing into the wide face or the edge of plywood. The lumber species will vary for some products which will affect your connector values. Some engineered wood is more susceptible to moisture content issues. Generally I'd prefer an engineered wood item or a machine stress rated item to a visually graded item for a critical tension member as the variabilities of wood is significantly reduced. But, read thoroughly, specify carefully and discount what the nice salesman says.

 

[msquared48]

Well, I wonder if the alleged problem could be due to long term creep under sustained load of any polymer binding agent between the strands, as with a Paralam, not necessarily a Microlam or LVL.

Mike McCann
MMC Engineering