Built up Composite Beam. 4

[malikasal]

Hey Guys,

I have 11.4m joists with concrete floor finishing, and i am thinking of using a composite system, the thing is we are a PEB fabricator and we simply love the Built up Sections.

did any body ever use a composite system with built up sections, we usually use one side welding between the web and flange but i am thinking with the high transfer load value on the flange this could be a problem?

any suggestions, hints, ideas or concerns on this ?




ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[KootK]

- I wouldn't think this fundamentally different from any other composite beam design.

- While one sided welding tends to shock non-PEMB engineers, I've looked into it and it's legit. Your flange to web weld shear demand is what it is based on your analysis. If one sided welding can get that job done, and I'm sure that it can, I'd have no problem with that.

 

[JoshPlumSE]

The weld is continuous, right? Same material for web and flange? If so, I don't see any fundamental differences. Though I would prefer to see top flange weld to be on both sides. And, you definitely need to check it for shear as it should have a higher demand than most non-composite beams.

 

[TehMightyEngineer]

Though I would prefer to see top flange weld to be on both sides.

Curious, what's your thinking regarding this? Shear buckling I assume.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL)
American Concrete Industries

https://americanconcrete.com/

 

[JoshPlumSE]

Not any real deep, technical thinking.... Just the one thing about this that pushes the borders of my comfort zone.

My thinking was that (at least for relatively thin flanges) you get some localized issues where the shear studs connect to the top flange. I've seen pictures where the studs come close to burning through. I have a minor concern that this could cause problems when it lines up right above the one sided web to flange weld.

Even if it does affect the web to flange weld, the effect should be pretty localized. Probably wouldn't be a systematic problem for flanges of reasonable thickness and studs spaced at 12" or more on center. However, it's just one of those things that doesn't sit quite right with me and pushes me a little outside my normal comfort zone.

 

[BridgeSmith]

Depending on the bracing conditions, I might have concerns with welding on only one side of the web due to the lack of lateral stability provided by a single point of connection to the flange (it's almost a hinge), as opposed to 2 points, even if they are only a 1/2" apart or so.

 

[dhengr]

Malikasal:
The flg. to web weld design is almost always governed by the shear flow at that plane, and that will be higher with the much huskier top flg. The single fillet weld obviously has to account for this. I’ve always been a fan of balance and symmetry in these kinds of welds, but this costs a little more. There is nothing wrong with the single sided weld, it is less expensive to fab. and that is what you PEB people are selling. Concentrated vertical or lateral loads on the top flg. (top flg. bearing and web crippling); uplift or top flg. twisting (tearing at the weld root); torsion and lateral loading, just don’t exist in their world, and on these details. They have provided the min. weld throat for the horiz. shear flow, on their min. weight/strength beam and that’s all that counts/matters. Don’t put an extra 2lbs./ft. of load on that beam, no new loads, concentrated loads, unbalanced loads or other than uniform min. load, or you will have a lot of trouble trying to make things meet the code with a positive margin of safety. And, you won’t even have the benefit of their software which uses up every ounce of redundancy or member overstrength from the get-go. The bldg. buyer is not informed of these issues, he is buying the least expensive enclosure from the floor slab upward, the rest is someone else’s problem and expense. Five years later when he wants to hang a 500lb. hoist from the roof structure, that’s his problem and the PEB people are long gone, or usually won’t return his phone calls.