Minimum edge distance requirements for built-up beams 1

[JaviG]

I am having difficulties finding the minimum edge distance requirements for built-up beams. I am designing a guardrail 4ft high which is anchored to a built-up beam (i.e (3) 2x6) as shown in the picture attached for a 200# point load. NDS - 2015 didn't have much info on built-up beams. I was planning on using 4D as my minimum edge distance. Any information or reference material would be highly appreciated.


[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1552355495/tips/scan0132_jdee1h.pdf[/url]

 

[txeng91]

Technically it’s 2D min for shear perpendicular to grain and 1.5D for withdrawl, which you have both. Regardless, industry standard is to bring the post down the face of the beam and provide a positive tension connection to a perpendicular framing member to limit forces in connections and minimize reliance on torsional forces in beams (see link below). Your detail could theoretically work, it’s similar to newel posts that are commonly used in residential applications at lofts and stairs, but I would question its effectiveness over long runs. If possible bring the post down the face of the beam as shown in the details and either resolve the torsional forces into the joists framing into it or to blocking between joists if the framing is parallel.

https://goo.gl/images/W4ZZ7a

 

[chorner26]

But what is the minimum edge distance for the interior face of say 2-2x6 built up, not the exterior edge.? Is it still the 1.5D W' (Withdrawal) and 2D Z' (Shear perpendicular to grain). The reason I ask this, is that is common practice in say Texas and Ohio to use built up 2x10 headers to create 6" wide members and I can't believe people always nail studs into the member at the exact right nail distance.

 

[txeng91]

I don’t know that the code really addresses edge distance for multiply members. I wouldn’t think that a lag screw would be as effective in withdrawal or shear if it is placed too close to the joint in the plys. You could technically still make the edge distances work for each individual ply if you hit right in the middle of each ply with a 3/8 lag. Considering this is a moment connection, stiffness and strength are a lot more critical than nailing of studs like you mentioned. You may consider going with a solid member and through bolting if possible. Would be way easier to tighten up in the future if the posts become loose. Also check to make sure you’re resolving the torsional forces on the beam through the joists or decking