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Beam span

Started by Neil_B, October 16, 2003, 02:58:35 PM

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Jim_Rogers

My books have a listing for "Red Maple" and for "mixed Maple". So in order to give New_Sawyer a good answer we'd need to know if it's "red" Maple or in the mixed category.

Don: Are you looking for the Fv value? That is shear parallel to grain? If so I have some of those numbers, in a chart in one of my books. I can email a copy to you if you send me a pm and give me your email address, I'll scan them in and send them right out to you.

And in continuing this thread, we need to know the width of the building to determine the actual amount of roof that's being supported by the log doorway header. And the shape of the roof whether or not there is a dormer over the log doorway or not.
Jim
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Jim_Rogers

Don:
I used my beam check calculator program and entered the values from the my book for Mixed maples. And used the 9550 lbs from your figures, and the beam fails all the way up to 14" x 16" the largest setting the program will allow.
I did a check using a round log and it failed all the way up to 24" diameter log, again the largest setting allowed.
So there is some definite problems with using "mixed" maple and the span or the amount of roof being held up with this beam.
Jim :P
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Neil_B

Yikes, you guys are really working on this :o thanks for all the input.

By the sounds of things, wood wize, I think I will be better off spending the money on  a steel beam. I have one in my garage spanning 24' so I know another should work on this. I'll check my code book on this to make sure it is close to the same load. The beam in the garage is mainly just supporting the floor of my shop but not snow load so I'll have to double check the ratings.

Jim, Don has the correct dimension for the width/ depth of the building at 16' so those numbers should be right. I may have to hold back on this for a bit though. Just went in to see our building inspector and he's OK with the building but not with the zoning of the property. :( May have to involve a lot of red tape before I go ahead and finalize the drawings.

Thanks again for all the input.
Neil
Timberwolf / TimberPro sawmill, Woodmizer edger, both with Kubota diesels. '92 Massey Ferguson 50H backhoe, '92 Ford F450 with 14' dump/ flatbed and of course an '88 GMC 3500 pickup.

Don P

Neil ,
I'm like a pig in a puddle  ;D
Also look into a parallam, microllam or flitch plate. My calc ran the parallam a little heavier than the co's literature, I'm reading a 5.25 X 12 should work.

Jim,
Exactly, Fv is what I lack. Check your messages, Thanks.
No sorry necessary, the misread was feedback on my "artwork" ::) :D. I've gone back and used bigger fonts on it.
I was using the lowest values I have for maples in my example. Fb, Fiberstress in bending for red is 1450 psi, for sugar, silver and black it is 1150 psi, I used the 1150. I used the lowest modulus of elasticity (E) in my deflection figures earlier in the thread, silver maple at E=.94 million psi. I've got red at 1.39 and 2" less deflection (still about 4.3"). Running the same numbers on my log beam calc (1150Fb, .94E, 9500lbs, 228" span) I'm coming up with a 15 incher. What values do you give for mixed maple? It seems more conservative than mine, wondering if it is in the values or the program formulas?

Don P

Joist Sizing:

A joist is basically a small beam, normally considered to be uniformly loaded. Around here they are typically designed for a 40 or 50 pounds per square foot loading. A joist is normally limited by deflection, it gets too bouncy or sags enough to crack plaster before it is in fiberstress trouble, always work all the checks to be sure though.


Going back to our same example, lets run 16' floor joists across the right side of the building on 16" centers. Each joist will support an area halfway to each adjoining joist. 8" along one side and 8" along the other side, 16" wide by 16' long. The joists are in blue, the area of bearing on one is in green. I like to work it like a board foot calculation...
(192" X 16") / 144 = 21.33 square feet
21.33 SF X 50 PSF = 1066 pounds
I like yellow pine for joists, I'm guessing it will take a pretty decent 2X12 so will start with a no.2. Don't forget to plug in actual dimensions, in this case I'll plug in 1.5 x 11.25.

Run it and it comes up larger than needed in fiberstress and fine on deflection (I used loblolly)...try to economize go to a 2 x 10, deflection fails, too bouncy. As a rafter with the same loading the 2 x 10 would be fine, more deflection is allowed there, Fb typically limits rafters.

Shear is fine.

I have this in tables...that would be the correct way to spec this, My CABO book says that 2 x 12 is good out to 19' 1" and a 2 x 10 is only good to 15' 8". CWC book says 18'10" and 16'1" respectively. Now with wall framing the span will work by code at 2 x 10, its near the limit, judgement call, I would bump up if at all possible. Code is limiting to 1/360 span deflection (a 15' span would deflect 1/2" at design load). Many floors are now specced at 1/480, consumers are wanting stiffer floors nowadays.

Rafter? Same way, just use horizontal clearspan not the angled run length, deflection can be up to 1/180 span, my calc is set up to read 1/360th so it can be double the allowed deflection number in a rafter. These are minimums, you can always go bigger.

Don P


 This is a flitch plate beam pic I had. The beam is a sandwich of 9" microllams around a 1/2 x 9 steel plate, bolting was specced by the supplier. I drill several small holes in the plate and nail it to the first LVL, drill one way, assemble the second microllam and drill back from the other side, then bolt. Usually the guys upstairs at your local truss plant can spec these.

Neil_B

I was thinking of still using the 6" x8" beam that I milled. Getting 2 lengths of 3" angle iron and welding them together to create a "T" then inserting into a 2 3/4" groove in the top? or bottom? of the beam. Then bolting through the flanges created as well as through the beam and steel in the groove.
Does this make sense?? ???
Timberwolf / TimberPro sawmill, Woodmizer edger, both with Kubota diesels. '92 Massey Ferguson 50H backhoe, '92 Ford F450 with 14' dump/ flatbed and of course an '88 GMC 3500 pickup.

Jim_Rogers

New_Sawyer:
I can understand your wanting to use the beam you've created. But sometimes you have to think things out, more.
First if I was going to do what you intend to do, make a saw shed, I'd want it to be the best and last a long time. You don't want to have to take it apart in a few months when the snow is all over it, with your mill under it, when it's collapsed onto your mill.
Next if I was going to try to cut the maple and put in a steel t-shaped beam, I'd buy a steel t-shaped beam not weld one up. If I was going to buy a steel beam I'd buy one big enough to do the job without the maple.
Now there are other solutions.
You need to lower the weight on this beam until it doesn't fail, in all the calculations. This can be done by redesigning your shed. Who cares if the shed roof doesn't look like your house roof? Does that really matter? It's a saw shed.
Some solutions would be to put a dormer over the log door and which would relocate all the load over this beam to the valley rafters, and then to the posts on either side of the door like this:



This could work as the load of the roof is shifted from the beam over the door opening to the sides.

Another way to do it would be to buy or build a truss for holding up the roof over the log door.
If you reduce the overhang of the roof over the log door area then you'll reduce the load on the beam.
Increase the roof angle will somewhat reduce some load to the beam by making the snow load duration shorter, but will increase some wind load on the roof.

To date you've not told us several things that we need to know in order to help you figure things out.
1. Type of maple? do you know?
2. Amount of roof overhang? You said a 16' wide shed, but you didn't say how many feet, if any, of overhanging roof. This is important because it will add to the load.
3. Intended roof pitch 12/12 or less?
4. Type of roof? shingles over boards, standing seam metal roof? These two roofs have different weights per square foot for figuring dead loads of the structure.

Some of the above answers will help us to understand what you want your shed to look like and how much of a load will be on the beam.

Now I'm not saying you should not use that beam at all, but if the figures don't add up then you should consider not using it as it might not be the best thing to do. If you decide to build your own truss for the header you maybe could use it as the bottom cord.

Keep thinking about it.
I heard it once said, 80% planning, 20% execution. (Plan it right, build it right).
Jim


Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Don P

Neil,
Where is the best place to use steel in a beam? The bottom. The label on the first section of my calc, extreme fiber, refers to the extreme outermost fibers in tension. In a beam that is typically the bottom edge. Fb in steel is more like 24000 psi instead if the 1150 we used for soft maple. Modulus of elasticity, used in the deflection calc is close to 29 million psi instead of the .94million for soft maple. I am far from qualified to tell you how to blend the materials safely.

Work the same problem with the highest values allowable for the strongest maple. Red Maple has an Fb of 1495 instead of the 1150 I used earlier, the numbers are still way off.

Do it another way, block the beam up on cinder blocks. I'm guessing about 18 drums of water, that would be a stack about 2 high or 95, 100 pound sacks ...at that load my mind says no way

Do it another way, run the calc using a red maple 2 x 24, same span and load (228", 9500lbs)...it works, same number of BF. Not suggesting you try to get a 2 x 24, that looks like a parallel chord truss, Just showing another way of looking at it, your beam is too shallow. Or another rule of thumb, deeper is cheaper.

I like the gable over the doors, it keeps the entry drier too.
 I've seen a steel triangular truss with a rod down to the sagging header sitting atop a shed roof, farm tech :D.

Neil_B

Some things have changed recently so a redesign is under way. As soon as I revamp my drawings, I will stick 'em on here for you guys to check out.

Jim, that beam is a sugar maple.
Timberwolf / TimberPro sawmill, Woodmizer edger, both with Kubota diesels. '92 Massey Ferguson 50H backhoe, '92 Ford F450 with 14' dump/ flatbed and of course an '88 GMC 3500 pickup.

Jim_Rogers

To Don P;
At the recent conference I got some new info on NDS specifications.
In the most recent published books, which was in 2001 the shear values have changed. It seems that someone who works for those who publish them rechecked all the figures and it was determined that the values were incorrect and that the had be published wrong. Somehow the values were subtracted twice or something like that. So now the new book has new values that are twice as strong as the old values. But don't do anything until, we, you or I, receive it in writing from the NDS. :P
We need to be sure about this.
But I though it's pass it on to you.
Jim
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Don P

 :o
Holy Big Beams Batman...glad the error was in that direction not the other. Although the values you sent do not appear low in comparison to others I've seen, I'll not enter the shear values till you get new ones. I'm still entering NDS Fb numbers and was going to do E values as I have time. I haven't posted that version yet but have been denoting NDS values with a + sign behind them. It was a tossup over the weekend...sunny and 70, I sawed instead :D.

Thanks for the heads up!

Don P

 8) 8) 8) 8)
Check out this joist and rafter calc.
http://www.awc.org/calculators/span/calc/timbercalcstyle.asp
Jim sent me a link for their publications and I was surfing their site. You da man Jim!

This was the publications list Jim sent me.
http://www.forestprod.org/awc/index.html

Jim_Rogers

Don P:
What we need to find now is a calculator that will allow us to put in any size beam.
I have some others sites I need to research to find one, I'll let you know when I do. :P
Jim
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Neil_B

Hi guys, figured I'd better update you guys.
 Still working on new plans but now I'm looking at a 14' by 85' building instead.
Instead of one 19' opening there will now be 2 at either end of the shed. Logs go in one and lumber, edged and trimmed, out the other end. Have a line on 2 steel beams, 5" x 12" I think, from the township, so waiting to hear back from them on whether they are going to keep them or not. Came out of a building in town that burned down a couple years ago, but they don't look like they were scorched at all.

Been keeping a watch on this thread and some very interesting info is coming up. Thanks.
Timberwolf / TimberPro sawmill, Woodmizer edger, both with Kubota diesels. '92 Massey Ferguson 50H backhoe, '92 Ford F450 with 14' dump/ flatbed and of course an '88 GMC 3500 pickup.

beenthere

I'm curious why you are going so narrow (14')  ???

I would expect I would feel real confined in such a narrow and long building. But figure you have a plan, or a restriction that makes sense.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Neil_B

Will post a pic of my layout. Everything should flow from one end to the other. Just need it wide enough to work in as narrower is cheaper and longer is easier to layout without tripping over things ;)
Timberwolf / TimberPro sawmill, Woodmizer edger, both with Kubota diesels. '92 Massey Ferguson 50H backhoe, '92 Ford F450 with 14' dump/ flatbed and of course an '88 GMC 3500 pickup.

rllintz

I have a unique situation that I'm having trouble working out. I am making a bent with about an 8/12 pitch that spans 30'. I'm using red and white oak. It will not have a roof. It's for an entrance to a ranch. It will have two top chords, a king post, two struts, and a bottom beam. Here's what I'm thinking so if anyone has any comments I'd greatly appreciate them.

The materials are red and white oak. 

2 posts. 10"x10"x8' 
2 knee braces. 10"x10"x6'
1 top plate. 10"x14"x32'
1 king post. 10"x10"x8'
2 top chords. 10"x10"x17'
2 struts. 10"x10"x6'

My concern is whether a 14" beam can carry the load without sagging. There's no roof or snow load. It's just a bent at the entrance to a ranch. Please if you have nasty comments just don't bother responding. Constructive comments are greatly appreciated.  

rllintz

I forgot to mention that the 10"x14"x30' beam will not be scarfed. It will be milled to length. 

Jim_Rogers

I can understand that this is an entrance to a ranch, but 8' post seem kind of short.
Will they be up on some concrete piers to get the clearance under the bottom chord of the truss?

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

rjwoelk

If you need to get a moving truck or semi in min 13'6" go 14 or 16 ft clear.
Lt15 palax wood processor,3020 JD 7120 CIH 36x72 hay shed for workshop coop tractor with a duetz for power plant

Don P

You won't be wrong using 60 lbs per CUBIC foot (12 BF) for green oak.
Then plug it in here;
Untitled (forestryforum.com)
That is checking the wood strength, the joinery is the next kettle of fish.

A metal cap formed for the top will help it last longer. And of course the more white the better. I borate and then put a water repellant finish on porch posts and such.

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