Fasteners to Nail Built-Up Column

[sswan60]

I’m designing a 60’ W x 80’ L, open sided agricultural roofed post frame structure that will sit on top of a concrete wall. I’m trying to use nail built-up 4 ply-2x8 columns. The columns are orientated so that the knee braces are attached to the wide dimension of the column laminations. No problem. The header (rim) beam and the wye braces are to be attached to the narrow dimension of the column laminations. I’m having a hard time finding fastener design guidance that address’s fasteners into the narrow dimension of built-up columns. If the nail built-up column is constructed per NDS can I treat the column as a solid column for fastener edge and end distance considerations?

 

[JAE]

Not sure I'm following you on this totally. Can you post a sketch?

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[sswan60]

Here is a picture of the header beam at each column. Screws would be used to attached the beam into the built-up column. End distance for the fastener in the side member is straight forward, It's the requirements for the main member I'm looking for information on. Simpson said their screw load tables would not apply for this application

 

[SlideRuleEra]

See "Bending Properties of Four-Layer Nail-Laminated Posts" by the USDA Forest Products Lab.

There is also an ANSI Standard for "Design Requirements and Bending Properties for Mechanically Laminated Wood Assemblies".

Google on "ANSI/ASAE EP559.1" to located an older edition.

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[sswan60]

SlideRuleEra, maybe I missed it in the documents you linked but I don't think that's what I'm looking for. I'm not looking for information on the design of the column but fastening side members to it considering the laminations. Is the edge distance from the whole assembly or each lamination, etc.

 

[SlideRuleEra]

sswan60 - Sorry. IMHO, side members should be bolted through all of the laminations. Nailed laminated columns behavior is complex, I would want the fastener (bolt) to engage all laminations.

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[JAE]

Could you put a connecting angle on the back side of the side beams and fasten into the wide sides of the column?

Also - if your knee brace is connected to this wide side such that the column has significant bending which causes sliding between the laminations, you have a serious problem in that your connections between lams will require a LOT of fasteners to work. This is more than the built-up column provisions of NDS Section 15.3.



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[dhengr]

Sswan60:
You can buy GluLam columns of that size, made up of 4 – 2x8’s, and you can get them pressure treated too, for their bearing on a conc. wall or pier found. They are sold specifically/primarily to the Ag. and post-frame building industry for this type of bldg. You might consider cols. made from 4 – 2x10’s so you could cut a horiz. seat/notch in the top of the col. for the perpendicular beams. Then you have a whole different loading condition on the beam connection hardware at the col. The beam is supported in bearing and held to the col. with the fasteners. Your detail is problematic for both end and edge dist. on the beam and for the bolt or screw edge dist. on the nail lam’ed. col. plys. The end and edge dist’s. from the NDS are minimums and probably not adequate (at least need some serious engineering thought and judgement) when both a shear loading and end moment component are applied to the bolt/screw, thus causing end splitting or tension perpendicular to the grain near an edge. Then, as JAE mentions, on all of your connections on your cols. you have to pay considerable attention to getting your fastener loads into the inner plys, not just the outer 2x ply. That is more nailing, bigger bolts or screws, etc. That said, here are plenty of farm and post/frame bldgs. standing out there, essentially with your detail, if you don’t care about good/sound engineering, or you don’t care which bldg. code you don’t follow. There are also a bunch of instances where your type of beam connections have failed.

 

[sswan60]

Appreciate the comments about the nail laminated columns. I plan on pursuing the use of GluLam columns as mentioned.