Engineering questions - steel laminate beams

[Jim Timber]

I had thought about that Eddie. I don't want that space crowded with vertical posts. It might end up getting a pool table or my audiophile gear someday, so I want to keep it flexible.

One of the guys over on Arboristsite gave me some numbers to use for wood, and I plugged those into Beam Boy 2.0 for a 12x12" 24' long. Not accounting for the 1460# beam itself, the deflection was near 3/4" with a 3,000# point load on the center. Since a 50lb/sf live load would be 7200# for a 6' wide section of floor (this would limit the middle beams to a 6' span having to carry both sides of the floor to the full 12' column width) it didn't work out to very favorable for such a structure. I'd have the same supported span of (3) 4" wide engineered trusses, but with over a thousand pounds more dead weight to hold up in the process. Erecting them isn't such a big deal, since I can lift that with my loader with ease, but that's a lot of work to get a beam cut that long out of good wood to then not even have the same strength as the pre-fab options.

Looks more and more like I should just suck it up and build or buy some stick trusses. I could build them with aspen (I have at least a hundred cords of 12-14" DBH quaking aspen that I want gone) and OSB or plywood and instead of having small gussets (to replace the metal plates), I could do a full profile side face to make it easy and extra stiff. 2 sheets of plywood (16" deep truss), some construction adhesive, and nails would get me a 24'er.

I also got a timber framing book on the way from the library.

 

[dstig1]

Sounds like very familiar troubles... You run into some good ones, but it seems the majority are bad. Our main guy is universally hated. He has a guy that he subs out to on occasions, and he is decent, but I rarely saw him. The sub did my main panel install inspection for when I connected the house panel to the service (main service is on the shop). He watched me wiring it up with the electric co guys there (who even helped me pull the last bit of big wire!) and said "it sure looks like you know what your doing, so I'll go look at the house panel while you wrap it up" The other guy would have made some wise-***** comment and smirked his stupid smirk while implying I didn't know what I was doing. Never met anyone who had a nice thing to say about him.

 

[GLyford]

I think what Eddie is getting at is making the two long "monitor" walls into trusses, think covered bridges and such. You could effectively have a wall-height flat topped (square) truss along the length of the building, at your wall spacing either side of the center space and resting on larger columns at each end. So no extra columns in the upstairs or downstairs space. Some larger columns in the end walls. Then either smaller trusses or stick built roof between and perpendicular to these two building-length trusses over the upstairs space. Being wall height, you would have a lot of section height to work with. It would replace the conventional stud walls in the upstairs monitor space.

 

[GLyford]

My temptation would be to do the exact same thing with two steel beams, to directly support the upstairs "monitor" walls. As others have pointed out, there are ways to use metal beams so that they do not project down into the shop space. For example, plate both sides of webs of the beam with 2x and use hangers for the ceiling joists on the two side bays and across the floor of the center bay.

Personally, I love seeing the bones of a structure like that and would come up with some way to flaunt them, be it a wooden truss or steel beam or steel open work truss.

 

[Jim Timber]

The upstairs monitor section will have regular post spacing of 8-12 feet (haven't decided yet) along the walls. The problem is that the span between the two walls is 24' and the whole area over and under it needs to remain open.

The roof above the upstairs in the center will be scissor trusses and spanning 24' with those is a breeze. The floor on the other hand, is a little too wide for conventional timber beams, so floor trusses are looking like the only viable solution. I can outfit the whole floor in trusses for the cost of a pair of I-beams.

 

[jim_wilson]

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.

Sounds like you want to do is exactly what I did in my barn when I built it.

I have a room over the front half of my structure - and I wanted to have a clear span underneath with minimal supporting columns.

What I got was a large steel I beam - that then had 4 pieces of LVL sandwiched in. I hung Weyerhauser TJI-560 wooden I-joists off of that. The total span is 28 feet in width - so the I-joists are nominally 14 feet long on each side. The steel I-beam is 24ft long - and is supported by one column on each end. I'm recalling this from memory - but I believe the columns are 4" in diameter - with 1/4" wall thickness.

This was all approved by my local building department - and has been in place for a few years now. I spec'ed that I wanted a high load capacity bearing capability for the floor that the steel I-beam supports - and I can tell you that it's solid as a rock. I've got a bunch of 5 gallon pails of ballast that I removed from the tires in my tractor stacked up there - and it doesn't seem to matter one bit.

If you want more detailed specs on what I used for a beam - let me know and I'll take some measurements or see if I can dig out the original engineering specs that the steel supplier gave me.

 

[jim_wilson]

This is the only pic I've got online right now that shows the structure of the floor - if you're interested I can see what else I have or take some more.

 

[GLyford]

The upstairs monitor section will have regular post spacing of 8-12 feet (haven't decided yet) along the walls.

OK, so if I understand this right you are saying the width of the monitor section is the 24' span, not the whole building, which is even wider, and you will have posts to the ground floor along the monitor walls.

I was thinking the under space was 24' wide and the monitor space was like 10 or 12' wide, with the walls for the monitor section resting on the clear span.

Maybe you can post a napkin sketch with dimensions on it or something to give us an idea of what we're looking at. In particular, the width and locations of the doorways at the ends.

I am thinking a metal beam like Jim posted above, resting on posts in your end walls at either midspan or the 1/3 and 2/3 points, as your door/wall configuration allows might be your best bet. If you're planning for a single wide door opening, then perhaps a serious overkill door header to support said beam.

We're visual people, if you can give us a better way to see your conditions and constraints, we may have some better ideas.

 

[GLyford]

Also, if your monitor posts are every 8 or 10 feet, you are planning beams at that spacing, and then joists parallel to the length, yes? In which case, the end walls don't really matter, you just want each of those beams to be sufficient...

 

[Jim Timber]

The monitor section will be 24', the outside lean-to's will probably be 16' or I might bump one of them out to 24' for additional parking from the side. I have a 10x15' room in the back of my current shop that's a nice size for machining (my surface grinder lives in the corner of it as does my air compressor), so I think if I had the manual mill and lathe tucked in on the outside of the main room with a little gantry crane, that'd be nice. I don't need an overly tall ceiling for either of them. Even my current CNC mill would fit in one of those little bays, but I hope to be getting a bigger one which might not, so it'd still be in the middle area of the first floor somewhere.

I think just building some trussed joists is the way to go for the middle span of my shop. What Jim W did wouldn't work, because I can't have the post in the middle of the floor to support the central beam. I want to be able to add another pair of rails beyond the 24' runway beams my current bridge runs on that will allow travel the full length of the first floor down the middle. I'll be able to pick up something out of the back of my truck or off a trailer and roll it to the other end of the building on the hook (that's how I move my machines now - it's awesome! ).

The lean-to's will provide the lateral support for the central posts. The central posts will be gusseted to the horizontal beams. The ceiling will be trussed across the monitor section and it's beams and posts will be gusseted. The only real issue is that the second floor is strong enough to handle the weight of whatever I end up putting up there, and I think some plywood sided glued and nailed trusses should do the trick.