Nail Laminated column (pole barn)

[EngineerJack]

Hi ALL,

I am designing a pole barn, and the client wants to use Triad Building Components Nail Laminated Columns. I have the manufactures report and from what I can see the columns have different Fb values based on different locations in the column and at the splice joints. So what value should I use for designing this column? If the max moment happens at the ground, the value of Fb=1250psi, but the upper portion is Fb=1950, and the spliced region is Fb=525psi. I'm trying to using enercalc column module, and the best I came up with is to assume a glulam column, species=sp, with a N2M10 layup at 4 lams, i.e., Fbyy=1750, Fbxx=1400. This squeaks by but Im not sure that this is conservative.

Maybe I need to assume Fb=1250, but then why does the mnfg even show a higher Fb value? And what about the splice joint, so i need to check the stress at that location and ensure demand is less than Fb=525?

Any advice is appreciated.

 

[phamENG]

You can use Enercalc to do an analysis, but you can't rely on its code checking. You'll have to do that on your own. You'll have to overlay your bending moment diagram with the capacity diagram for the product you're using. That can be done graphically or using a spreadsheet to calculate the demand and some interval of y and then compare those results to capacity at the same point.

 

[ntattose]

If I were doing this, I would generate a moment diagram by hand. From that I would determine the moment at each location where Fb changes. At each of these locations determine
fb = M/S and compare that to Fb. If you need to check deflection, that may be a bit more tricky since the "E" will change with each material change.

 

[lexpatrie]

EnerCalc is flat out not adequate for this task.

 

[EngineerJack]

Thank you all for the feedback. ntattose posted exactly my first plan, but the overall design is for a pole barn, and I've only considered that as a "cantilevered beam" from a moment diagram perspective. Therefore, the moment diagram is maximum at the base of the column (looks like a triangle), and SYP (southern yellow pine) is NG, let alone the splice joint. After reading the mnfg's report a bit more over the weekend, they're using springs at the base of the column to model soil interaction and then at the top to model attachment into the diagram. With that model, the moment diagram looks more like an S, and sure enough, the joint is very close to the inflection point, and in their report, that controls the capacity of the column, its 1.0 unity at their design load of 160plf.

I have RISA3D and SAP200, and I can model all this, I could even use their 160plf design load and back out an answer. However, the spring constants for the soil/diagram are listed as a warning in the mnfg's literature, and their capacity report is "preliminary design and pricing purposes only." I'm sure my client would love to hire a geotech and pay me extra to build a FEM model of their barn!

At this point, I'm going to use the IBC 1807.3 and regular old glulam columns.

Thanks again,