sizing I-beam for shed

[bdog]

I have a 30x40 metal building.It is 40 feet long in the direction that the peak of the roof runs. I am wanting to add on to the side of it a lean to / shed. Basically a roof with a back and side wall and open front to store implements or whatever under out of the weather.

I have googled and searched and can not find any tables for beam size requirements. I am trying to figure out what size of beams I will need to support the structure.

I was thinking three beams 20 feet apart and a width of the shed of 24'. The beams would then have purlins welded to the top of them to screw the R-panels to.

 

[Shield Arc]

Will this help? If not if you can give me an idea of what kind of loads you'll have I can look it up.
This chart is for the beam being uniformly loaded, if you want point loaded, divide the number in half.

 

[bdog]

Thanks for the reply.

The chart is probably what I need but I am not sure I know how to read it. What are Kips and how do I determine how many I need to be able to support? What is the standard required for a roof?


I am in Texas so we don't get major snow. I don't ever plan on putting anything on the roof. I just need the beam to be able to support itself, 8" C purlins, and 26 gauge R panels. There will be three beams spaced 20 feet apart and the span is 24 feet. (My structure will be 24 feet wide and 40 feet deep). I plan on putting the 8" C purlins running in the 40' direction spaced 4 feet apart.

 

[Shield Arc]

A kip is 1,000. pounds.
You'll have to figure out all the weight that is going on the roof, plus snow load. Then figure out how many posts / span.
I scanned another chart with smaller beams for you.

 

[sjames]

1kips = 1000lbs.

 

[flusher]

I have a 30x40 metal building.It is 40 feet long in the direction that the peak of the roof runs. I am wanting to add on to the side of it a lean to / shed. Basically a roof with a back and side wall and open front to store implements or whatever under out of the weather.

I have googled and searched and can not find any tables for beam size requirements. I am trying to figure out what size of beams I will need to support the structure.

I was thinking three beams 20 feet apart and a width of the shed of 24'. The beams would then have purlins welded to the top of them to screw the R-panels to.

I'd go with K-series open web steel joists--like you see in Walmart stores--to support your roof. A lot less weight to lift than with steel I-beams.

 

[sjames]

Shield Arc,

Is the second chart you posted from the ASD or the LRFD tables?

As i understand it, LRFD uses different factors when combining load. You would need to multiply you live and dead loads by different factors to arrive at the ultimate load. Without doing that you could be in the plastic range for the beam but be under the value listed in the tables.

If its an ASD chart I believe you can just add your live and dead loads together and consult the table to keep in the elastic range.

disclaimer: I'm not an engineer, my understanding of ASD and LRFD my be flawed.

 

[Shield Arc]

Boy you got me, I'm not an engineer either! I've only been on one train in my life.:laughing:

Scanned from Manual of Steel Construction Allowable Stress Design?

 

[sjames]

OK, ASD it is. :thumbsup:

Allowable Stress Design (ASD)
Load and Resistance Factor Design (LRFD)

 

[IXLR8]

bdog- I had a similar issue, I ended up hiring an engineer to design my loft with steel beam supports, cost me $350. Worth it to me not to have any questions and to have a plan to work from.

 

[Shield Arc]

cost me $350.

That's a very good price. If nothing else peace of mind!

 

[LD1]

That's a very good price. If nothing else peace of mind!

google and download beamboy.

It is a very handy program. You choose your length and loads. Then choose beams of common sizes from a list to find the ones that will support the weight and still be within the l/360 deflection limitations, and still be under the maximum bending moment.

And you will have to account for the weight of that 8" c-channel as well.

Regular ole structural c-channel is 11.5lbs per foot for 8". Considering you will need 7 runs @ 40' length, that is 280 total feet. Which is 3220lbs. Plus the weight of the roofing, which will be minimal.

Your center beam will also be carying more of the load than the outers. Roughly half of that load will be entirely on the center beam. So 1610lbs divided by 24" would be a distrubuted load of ~67 lbs per foot JUST for the purlins. Roofing and a little snow may add to that.

Even at a minimum, if you design the roof to handel a 10lb per square foot live load, that is another 9600 lbs. 4300 on the middle beam. 4300/24 =180 lb per foot.

So figuring ~ 250lb per foot distributed load @ a minimum. with L/360 deflection you are allowed a .8" deflection.

This would require a beam with a moment of inertia of 80 or greater. Which would be a W8x24 or heavier in an 8". Or a W10x19 or bigger. Or about anything 12" an up would suffice.

Again, these are minimums, and The 8" channel is pleanty strong for the purlins @ 4" OC and a 10psf live load.

If you can download beamboy you can play with these numbers as well and see what you come up with. BUT if in doubt, hire an engineer. I don't know all the details and measurments and possible lateral forces, etc. This is just to give you a basic Idea of what to look for.

Disclaimer:insert all fine print that here that I cannot be held liable for anythingisclaimer.

 

[ecoslik]

We used 10" I-beams for 26' and 30' spans and 8" purlin on 5' center for the shed roofs added to our metal shop building in the thread that I posted:
"FEL -- now we have 16'+ lift height"
http://www.tractorbynet.com/forums/kubota-owning-operating/185637-front-end-loader-now-we.html

The completed, shed roofs were 30'x60' and 26'x60'. I love all the additional cover. :thumbsup:

FWIW, Mueller Metal Buildings made the sizing recomendations when we bought the materials. We are in Texas.

 

[bdog]

Thanks for all the replies. I will look into the beamboy. The 8" Purlins I am talking about are 8" C purlins not C channel. I don't know the weight but they are no where near 11.5# per foot. I can pick up and carry around a 25' piece. I get the concept though on sizing up what I need.

Ecosilk it looks like I am aiming to do exactly what you did only 40' long instead of 60' and 24' wide instead of 30'. It looks like you set all new posts/columns for the shed instead of tieing it in to the existing shop? I was debating on how to do this.

Is that square tube for the posts/columns?

Did you just auger holes and concrete in the posts or did you dig out a pier for each post and concrete it and set bolts and then bolt the post to the pier?

Thanks

 

[LD1]

Either way, with that kind of square footage, the weight of the roofing is minimal compaired to designing for a 10 lb per squar foot load. Which is the lightest I would design for.

 

[bdog]

Either way, with that kind of square footage, the weight of the roofing is minimal compaired to designing for a 10 lb per squar foot load. Which is the lightest I would design for.

Good point. 10lb/sq is roughly 10,000 lbs. I thought 3200lbs of C channel was heavy to have on a roof but really it is only 1/3 of what I need to be concerned with.

 

[LD1]

Good point. 10lb/sq is roughly 10,000 lbs. I thought 3200lbs of C channel was heavy to have on a roof but really it is only 1/3 of what I need to be concerned with.

Exactally what I am getting at.

Most floors/decks are designed for around 50psf

And even up here, we design for roof loads of 20 psf. And if you were to add sheeting and plywood, that would be roughly a 10psf dead load as well.

Another peice of advice though, if you havent got the beams yet, keep an eye on c-list. If your not in a hurry, something will turn up.
I needed two 30' beams @ a w10x19 minimum for a loft in the garage I was building. New price was ~ $900.

Found a c-list add for beams. I ended up with two 26' and one 21' w12x35 beams (about twice as stout as I needed) for $500. When I was done making two 30 footers, I sold the remaining peice which turned out to be roughly 14' for $200. So I only had $300 in the beams that are stronger than I needed vs $900 for a minimum requirement.

 

[ecoslik]

Bdog,

We set 16-qty, 20' long 4" square columns into holes that were approximately 48". The holes were overkill ... 125 bags of concrete. But, it gave me an excuse to finally buy an electric concrete mixer rated that works great with 160lbs of sakcrete or 240lbs if I'm not sloppy.

We have a sloped grade running accross the build site (2' between buildings where we did the 26' shed roof and 18" on 30' side). Once the posts were up, we surveyed a common level for the two groups of 8-qty columns on each side of the building. A concrete guy with a survey transom who has done a few slabs for us stopped by to do this for us on his way home one day. We wanted the finished shed roof to be 12" below the level of the finished roof height of the building. We cut the posts to achieve this step down plus to allow for the slope/pitch of the shed roofs. We found this to be an easier way to accomodate all the grades, existing conditions, etc. We used a 7" circular saw fitted with a cutoff blade to make these cuts; for the columns against the building, we finished the cuts with a sawzall since we couldn't use the circular saw to cut from both sides which is required when cutting a 4" column with a 7" circular saw.

I preferred NOT to penetrate the wall of the building to tie the structures together. Instead, we used flashing designed with the "R-panel" corrugation to seal the joint between the shed roof and the building. Yes, we had to screw through the flashing into the building and then caulk, but I preferred this to a cutting the entire 60' length of the building for structural and flashing penetrations which is what I probably would have done if constructing the building and shed roofs at same time. We had a large rain storm night before last, and there were no leaks.

Some might prefer structural connection between the shed roofs and building to prevent the shimmy that occurs without such connection, but since I am also installing some pipe fencing that will weld to these columns, I felt that I would get additional rigidtity that way. In fact, I welded in couple sections of this pipe fence already, and the shimy is nearly non-existant now.