Engineering questions - steel laminate beams

[EddieWalker]

I think the reason you can't find a calculator for anything bigger then 2x lumber is that there are to many variables. Same thing with spanning 24 feet. Just the sheer span creates issue of wood without a load on it that trying to find something that can span that distance, and also support a load is pushing the physics of lumber.

With residential construction, open floor plans are all the rage. Builders are doing everything they can to get them as open as possible. What happens all the time is they go too far and the house ends up moving all the time, cracking the sheetrock. The foundation is usually blamed, but it's the span of the lumber overhead that is causing all the problems.

All wood has it's limit. Even going bigger, wider and deeper, you will have a limit. At 24 feet, you are maxing out your span, which means that over time, you will have a greater odd of failure. Never max out anything.

Either go with engineered lumber, trusses designed and approved for your span and load, or steel beams.

 

[Jim Timber]

It just seems like I should be able to make something that would work. I could run a 1/2x12" metal flat bar down the middle of two wood cants and I'd think they would exceed the strength of a wide flange I-beam with sufficient anchoring (tongue and groove the edge into the cants and weld on some tabs to bolt them top to bottom through) - I just have no idea how to model that for calculating it's stress.

Buying an I-beam isn't out of the question. It's just not the solution I'm after. I want different.

 

[xtn]

50-psf live loading for general storage depends on what you're generally storing. I wouldn't use that for anything beyond typical residential attic space where I expected stuff like christmas decorations, cardboard boxes of old clothing, etc. Typical office cubical space would be planned at 80-psf. Light filing cabinets and shelving areas would be targeted at 125-psf. High-density filing/shelving would really go up into the neighborhood of 200 -to- 300-psf.

I would strongly be considering steel trusses for this application. Using dimensional lumber to span 24' with on-center spacing of anything reasonable and expecting a decent live load capacity without absurd deflection is just not going to calculate out. If you MUST use wood, still look into various truss construction, or plan on some big heavy beams spanning the 24', put them ten feet apart, and then span between those beams in the 10' direction with your dimensional lumber.

 

[xtn]

Oh...here is a tip...when you start "generally storing" stuff upstairs, put the heavy crap near the walls instead of out in the middle of the floor!

 

[Jim Timber]

I would strongly be considering steel trusses for this application. Using dimensional lumber to span 24' with on-center spacing of anything reasonable and expecting a decent live load capacity without absurd deflection is just not going to calculate out. If you MUST use wood, still look into various truss construction, or plan on some big heavy beams spanning the 24', put them ten feet apart, and then span between those beams in the 10' direction with your dimensional lumber.

This is exactly what I originally set out to do. I just don't have any way to model the designs and figured there's guys who've already done this or could maybe help a guy out and use their software to run some calcs for me.

I'm not going to use this space for storing engine blocks or 3 lawyers offices worth of paper. Mainly, it'll be a temporary dwelling while I build my main house. After the house is done, it'll become my office and general household storage. All my heavy stuff will remain on the main floor with a 5" or so concrete slab under it. I do want to keep the inside end wall open enough to send furniture up there (likely a barn door to close it off). If I tried hard enough, I could probably build that room to the golden ratio, and put my audio stuff up there when the house is done.

 

[franklin2]

I want to use the calculator in one of the previous post, they want too much info and I don't know what to plug in. If I go to lowe's and buy their lumber, what do they usually sell? I never pay any attention, I just buy what they have. What should I plug in for the lumber they carry in stock?

 

[Jim Timber]

Typical box store stuff is #2. It'll be stamped.

 

[Rustyiron]

Somewhere there must be a book with "tables" back from the day's when heavy timber construction was common.
Are you opposed to spaning the 24' with "store bought" wood? I am quite certain that LVL's would span that. Any time I've had "weird loads" the lumber supplier would send it to the manufacturer and they would spec it. The quesstion for them would be what depth member and the spacing. They may even have a floor truss or a TJI (wood I beam) that would work. We just used 12" TJI's @ 12" o.c. to span 24' with a normal living space (live) load. It did have a little bounce, but not terrible.

 

[Jim Timber]

I'd rather not have a stick built floor in this building. I agree with the old data suggestion, and will be headed to the library before too long to get my nose in the rest of the engineering on this building.

If it comes down to it, I can build stick trusses or buy them, and have a boring floor. I'd rather have the heavy wood if I can get it done within reason.

 

[Rustyiron]

I'd rather not have a stick built floor in this building. I agree with the old data suggestion, and will be headed to the library before too long to get my nose in the rest of the engineering on this building.

If it comes down to it, I can build stick trusses or buy them, and have a boring floor. I'd rather have the heavy wood if I can get it done within reason.

The older "heavy timber" construction that I (barely) remember seemed to rely on a heavy floor (thick deck), like several inches, for greater spans between the (fewer) supporting timbers, like 4', vs. today's dimensional lumber with typical 16" o.c. and a 3/4" floor deck.
I'm with ya on the "boring floor":thumbsup: