NDS Checking Built Up Beam

[NNC20]

I have a built up beam (T configuration) and would like to check capacity per the NDS Standards. Would I just adjust the area moment of inertia and the section modulus and use a flat use factor of 1.0?

 

[JAE]

Flat use is only for primary bending in a flat condition.

With a "T" beam made up of a flat flange and a vertical stem, the flat flange is not really bending so much as being placed in axial compression as a flange.

 

[dhengr]

Nncortes:
No, you can’t treat your “T” top flg. as if it were a flatwise bending member, using NDS allowable stresses for flat use, as mentioned by JAE. Find your section properties for the combined section, and then you must design the joint btwn. the flg. and the stem for the shear flow at that joint. Pay some special attention to that joint at the end of the beam member, so that that joint can’t even start to split or zip open, due to inferior connection at the ends. I’d have to give it some more thought, but if I had to, I might finagle a bit to adjust the top flg. allowable stresses which I could rationalize and defend, because it is acting a bit more like a compression member than what we normally think of as a wooden bending member. Furthermore, it is not acting in the orientation which it is grading would normally assume it was acting. There might be some advantage in selecting an improved grade of material for the top flg.

 

[NNC20]

I should mention that the primary loading would be on the stem, horizontal. The member is a railing.

 

[JAE]

So if you have a T section in horizontal bending your vertical stem isn’t doing much and the top flange portion is definitely not in flat use bending.