Engineering questions - steel laminate beams

[Jim Timber]

This is just an engineering problem right now. I'm not ready to buy anything, just trying to get the imaginary ducks in my head lined up.

I'd like to build a monitor style barn for my workshop, with a timber frame out of red oak. I want the center span to be 24' clear down the middle, arch braces at the connections are not acceptable (need it open at the inside corners for bridge crane). I plan on doing a truss configuration for the roof so that's easy to build for, but I'm not sure how to design the load bearing floor for the second story.

Select 2x12 is good for 16'9" from what little digging I've done. I don't have too many trees larger than around 15-18" DBH, and cut down into beams that will probably get me a 12" max width of heartwood in the first and second log (or first log if I cut them to 25'), but I'm thinking I'll be into sap wood by the time I get up 27' in the trunk.

My question is how thick and wide would a composite steel/oak beam need to be for a 50lb/sf live load at that span? I don't really plan to have anything overly heavy up there (it'll be utility space, and temporary dwelling while building the house), but I'd rather build it a little stronger than needed from the beginning. Also, could I make an I-beam with a steel web and wood flanges? Weld tabs onto the web and bolt to the wood?

- What width/thickness wood/steel would I need to use in the beam(s) to achieve this strength?

- Is 50lbs/sf sufficient for general storage or should I go heavier yet?

- How should I plan on protecting the steel from corrosion with the wet oak? I was thinking I could use a polymer bedliner product after they're drilled.

- With 8' or 10' bays, how many joists will I need for this floor system? I'm thinking this will be 24' or 30' long. The rest of the building will be open up to the roof, so this floor will only support half the structure. Hopefully that makes sense. I think the lean-to's should tie the inner posts together well enough to prevent the open center from racking.

Another question is whether I should do laminated beams or build trusses for these instead? I have no design considerations for aesthetics. I just love heavy construction and figure I'll learn the craft on the barn before building the pretty one with the house.

Any input appreciated. I'm pretty good with metal and balloon framing is a breeze. I want to raise the bar a bit on the next one so I'm asking for help where I'm out of my wheelhouse.


There's no building codes in my county, so I can do whatever I want. I still want it safe.

 

[aczlan]

Why not a composite wood beam (either the type that looks like a big piece of plywood or one with flakeboard in the middle and a 2" piece of plywood on the top/bottom)?

Aaron Z

 

[ishiboo]

This is just an engineering problem right now. I'm not ready to buy anything, just trying to get the imaginary ducks in my head lined up.

I'd like to build a monitor style barn for my workshop, with a timber frame out of red oak. I want the center span to be 24' clear down the middle, arch braces at the connections are not acceptable (need it open at the inside corners for bridge crane). I plan on doing a truss configuration for the roof so that's easy to build for, but I'm not sure how to design the load bearing floor for the second story.

Select 2x12 is good for 16'9" from what little digging I've done. I don't have too many trees larger than around 15-18" DBH, and cut down into beams that will probably get me a 12" max width of heartwood in the first and second log (or first log if I cut them to 25'), but I'm thinking I'll be into sap wood by the time I get up 27' in the trunk.

My question is how thick and wide would a composite steel/oak beam need to be for a 50lb/sf live load at that span? I don't really plan to have anything overly heavy up there (it'll be utility space, and temporary dwelling while building the house), but I'd rather build it a little stronger than needed from the beginning. Also, could I make an I-beam with a steel web and wood flanges? Weld tabs onto the web and bolt to the wood?

- What width/thickness wood/steel would I need to use in the beam(s) to achieve this strength?

- Is 50lbs/sf sufficient for general storage or should I go heavier yet?

- How should I plan on protecting the steel from corrosion with the wet oak? I was thinking I could use a polymer bedliner product after they're drilled.

- With 8' or 10' bays, how many joists will I need for this floor system? I'm thinking this will be 24' or 30' long. The rest of the building will be open up to the roof, so this floor will only support half the structure. Hopefully that makes sense. I think the lean-to's should tie the inner posts together well enough to prevent the open center from racking.

Another question is whether I should do laminated beams or build trusses for these instead? I have no design considerations for aesthetics. I just love heavy construction and figure I'll learn the craft on the barn before building the pretty one with the house.

Any input appreciated. I'm pretty good with metal and balloon framing is a breeze. I want to raise the bar a bit on the next one so I'm asking for help where I'm out of my wheelhouse.


There's no building codes in my county, so I can do whatever I want. I still want it safe.

I think you need to draw out what you are trying to do. If your plan is to span 24' and carry the posts that support the center roof and half the side roofs onto beams, you're going to find it's not at all practical.

I know you want to do heavy timber, but I would look for a company that could (not even sure if it's possible) build a truss that would make the roofline look the way you want it to, somewhat like a monitor, that would give you a clear space under. At 24' for the floor, wood floor trusses are going to be the way to go, especially since you have the lumber. 2x3 frame, probably 24" deep at that span. Use solid 1x or so epoxied for the connector plates. I'm not sure how you're going to be able to calculate this without going to someone with a truss calculator. I don't know you want to go any less deep or less wide than 3" width despite red oak being muchs tronger than the usual SPF, but the red oak will give you a larger OC.

50lb/sf is more than enough to store a car, so if deflection and flooring performance is not a concern I think it's more than sufficient for loading on a storage floor.

 

[bcp]

This is just an engineering problem right now. I'm not ready to buy anything, just trying to get the imaginary ducks in my head lined up.

Beware, there are lots of duck shufflers here. I'm one.

Composite beam: Think about the other way, too. A 2 x 12 with a 1.5 x1/8 steel strap on the bottom, for example, would gain lots of strength.

 

[Jim Timber]

I can do sheer/load bearing walls between the bays on the sides to support the floor. I'm not concerned with aesthetics on the ground floor, but would like to retain the timber frame on the second.

24" truss sounds a lot more do-able, honestly. Less material, less weight. Assembly time isn't too bad. Might take a couple weeks to build them (assembly and cure time) - and that's cool with me.

I'll sketch it out and take a pic to show what I have in my head. I know it's hard to visualize when you can't see the gray matter like I do. Despite being able to program a CNC mill, I'm horrible with CAD.

 

[Jim Timber]

Beware, there are lots of duck shufflers here. I'm one.

Composite beam: Think about the other way, too. A 2 x 12 with a 1.5 x1/8 steel strap on the bottom, for example, would gain lots of strength.

I'm open to any kind of floor construction that'll keep the upstairs out of the ground floor. :laughing: My machine shop will be below this ceiling, thus the bridge crane and extra headroom. I'd like to have the open end of the barn able to handle a 2 post lift someday which is why I'll be keeping it open on that end. The sides will be extra storage and materials, maybe parking too.

I got a big dose of duck shuffling when I first mentioned a concept for a moveable big building. I know who's here, and I know everyone likes to flesh things out to a fine degree - it's why I'm putting this thread on this site. You guys rock with lots of info, and I'm grateful for it!

So here's a quick drawing of the basic layout. The frame will be 12/24/12 on the bents on the open end, with probably 10' bays. The two story side will be 12/8/8/8/12. The ground floor where the second story floor is doesn't need to be open and will have storage on the outsides and might end up wider before I'm done fleshing the whole thing out. It might make sense to have at least one side of it able to park cars in, but that's easy to figure out since the doors would only be 16' wide. Wider lean-to's would be stronger as well. I have all kinds of space, so I'm not worried about this getting too big. I also have plenty of trees.

Drawing not to scale.

 

[Jim Timber]

I'd love to do something like this, but the balcony end would be exposed to our predominant winds and the floor sealing (water) would be a nightmare.

 

[RedNeckRacin]

I would look at the engineered wood truss systems and the composite I beams. I priced out some 20' wood trusses this week for residential use and they were $64 a piece. This was 16"o.c. and 10lbs dead 40lb live load. With the longer spans you are looking at, deflection will be a major concern as well as springy floors. Don't cheap out on the structural components of your building, build it strong enough the first time, it's much cheaper. The nice thing about the floor trusses is there is plenty of room for utility runs!

 

[Egon]

Check out some Farm Co-op's for some of their plans. Agriculture schools may also have some pretty standard plans.

 

[EddieWalker]

Maximum Span Calculator for Wood Joists and Rafters

That is a site that does span tables for different kinds of woods depending on the species and grade of the wood. Add your spacing and what load you want and it will tell you how far you can go. From what I just looked at, you can use Number 1 Red Oak 2x12's on 16 inch centers for a 50 lb load and only span 15ft 10 inches.

Laminating metal onto the side of each joist will add to your span, but at what cost? There is a point where you cross over from common building methods and materials and into the unknown. Using red oak complicates things. Going for 24 feet puts you into the dangerous side of things because you are pushing the envelope so far that if you don't get it perfect, failure is very likely to happen.

This is a job that I would require an engineer to design before I would take it if somebody was wanting to hire me. Too much liability. Too much risk.

You can get 19ft 7 inches with Southern Pine

Instead of spanning 24 feet to create your floor joist, I would probably look into spanning that distance with an engineered beam or going with a properly sized steel I beam. Adding to the fact that you want a carriage crane, going with steel I beams across the width of the building makes more sense if you can run your track for the crane under the beams for the length of the building.

Depending on the length of your building, space the steel I beams between 12 to 16 feet so you can span the distance with the red oak that you want to use. This will increase the thickness of your ceiling/floor considerably, but with a monitor barn, it wont matter that much since your second story roof height can be anything you want it to be.