Steel to wood beam equivalency?

[Jeff F]

Anyone know of any resources for figuring out what size steel beam would be equivalent to a given wood beam, and then using that to determine what post spacing could be achieved for a larger steel beam? There is a lot out there about sizing wood joists/beams based on use case (number of floors, live loads, etc.) but for steel you need to know a lot more of the details like permissible deflection and specific loads vs. a generic use case.

My application is that I have a 2-story barn that is roughly 36x72. It is constructed with beams built of 4 "actual size" 2x10s (not 1.5"x9.5") parallel to the long side (12' on center), with posts supporting them approximately 10' on center, although there is a span at one end that is 16'. The joists overlap at the beams so there is no changing the 12' spacing in that direction, but I may want to rework the beams so the posts are not as close together. Any final design would be with the help of an engineer, but for now I'm trying to get a rough idea of what would be possible. Could a 10" tall steel beam get me to a 24' span? The floor is going to be ripped out and replaced, so I can put post supports anywhere I want in the process.

The generic wood tables say that a 4-ply 2x10 supporting a single floor and 12' joists is good for 11'3" and that roughly matches the current spacing.

 

[Hank11]

We can only guess that you want to maintain headroom and have wider bays? You’ll get more answers if you lay out your desires more specifically. With the floor coming out you are starting over from the ground and need to figure footers for the new supports to hold up the new beam.

 

[loganb]

Ballpark you can double if not triple your span/distance between posts assuming a Wide Flange steel beam, the question is how much span you want. The beams are sized by weight per ft...more steel is more strong is more heavy basically. If you want to keep the existing 10" beam height there are several sizes that will roughly match that and vary dramatically in weight per ft and cost. A W10 x 22 appears to be able to approximately double your span....a W10 x 88 can probably triple it. As you reduce posts, your footers under each become more important and the beam gets dramatically more expensive so it's a balancing act.

Questions the structural engineer will need to know in no particular order

What is going above it...this drives the loads per sq ft

How much headroom do you need under the beam? The taller you can make it the less steel per ft it needs to resist bending

Any limits on how deep you can do the footers? If the floor is coming out already that makes it easier but likely going to want a skid steer with a big auger bit to dig the holes for the new footers

How much are you willing to pay to reduce the number of midspan supports. Heavier steel beam, fewer but bigger footers gives you more clear span area ....is it worth it?

 

[larry4406]

How much headroom do you need under the beam? The taller you can make it the less steel per ft it needs to resist bending

If he is going to be ripping out the flooring, he could then entertain a flush beam with the joists hung on the sides so as to increase/recover headroom...

Flush beams cause issues with passing MEP in the deck so be forewarned of this significant downside.

 

[manwithtools]

If he is going to be ripping out the flooring

Larry, I think the OP means ripping out the "concrete flooring", not the wood on the second floor???

 

[threepiece]

For my steel beam sizing I use empirical data from a book called Steel Construction Fifth Edition 1952 from American Institute of Steel Construction. It has numerous charts of various structural shapes and sizes and their capacities. Let me know if you would like me to post a picture of a relevant page.

 

[loganb]

For my steel beam sizing I use empirical data from a book called Steel Construction Fifth Edition 1952 from American Institute of Steel Construction. It has numerous charts of various structural shapes and sizes and their capacities. Let me know if you would like me to post a picture of a relevant page.

The Gold "steel bible" as it's kinda known is a great reference but if you have it I'm assuming you understand its only a reference point for mechanical property data and formulas. Having the data and understanding how to apply are different....and I'm admittedly only sightly better than a bumbling idiot

 

[Jeff F]

Answers:
-This is above it. The area that is in the lower level pic above, and the area I want to rework is on the other side of the walkway from where this was taken. As the structure is a bit complicated (there are supports from the sidewalls that go down to the joists my thought was that I should target having a beam that at least matches the strength of what is there.


-No limits to how deep the footers can be as far as I know

-More info on what I want to do with it in this thread. Basically I need to add doors and access for cars. One option is to put the doors on the side. In that scenario I have 12' wide bays which are OK but it would be nice to have not quite so many posts. Another scenario is to put doors on the long side which would be easier for access, but with the posts 10' apart it makes it tight for opening doors and general flexibility in parking things. The other downside to having doors on the long side is that the depth is 36', which is tight to have 2 cars deep and useful wall space.

-There is some wiggle room on the height in that area. If the doors are on the side, the height isn't really important. If the doors are on the front, I'd want to have at least 7' clearance. I need to find my measurements on the existing height. As you can see in the first pic and the thread linked above, the floor is at 2 levels and I'm not sure where exactly the floor is going to end up.

 

[atch]

I'm no structural engineer so feel free to tell me I'm an idiot. Could you eliminate every other post by using flat steel slabs, the same width as your existing wood beams are tall, through bolted on each side of your existing wood beams. Therefore resulting in:

• the existing wood beams still there
• steel on each side of the wood beams, bolted through side to side
• every other post removed
• strong enough to hold up the 2nd floor with half of the posts

Yes, I know I have no idea what would happen to the existing foorters under the remaining posts.

 

[danfromsyr]

I read your other post earlier and I still think you'd find most use by adding on a T-shape 'intersecting' gambrel addition.
and then keep that back barn floor/structure for the mundane garage use
more barn is more bettah

I'm willing to bet you wouldn't be that far off on the costs vs modifying your already modified vintage barn.