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Author Topic: Clear Span Roof Truss Calculator  (Read 7842 times)

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Offline Don P

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Re: Clear Span Roof Truss Calculator
« Reply #120 on: March 21, 2019, 08:40:56 AM »
Hmm, not real partial to one over another, I also like the Howe designs with timber compression struts and steel rod tension struts, I'll see if I can dig up a pic. We're getting into personal taste there though. I tell my clients "when this is done I go home to my house, this is your house."

FOHC is less prone to checking, that is not structural just aesthetic.
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Offline Sedgehammer

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Re: Clear Span Roof Truss Calculator
« Reply #121 on: March 21, 2019, 10:46:52 AM »
I meant for the pitch of the roof as to your preference of a truss.

Yes, each house is theirs that they go home to, but sometimes different view points and opines makes one think of something they hadn't and the different ideas can be married into one and it's better overall. 

Ahh k

Offline Don P

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Re: Clear Span Roof Truss Calculator
« Reply #122 on: March 21, 2019, 07:24:35 PM »
Check out fig 4-25 here;
https://docplayer.net/22941914-Heavy-timber-frame-construction.html

When we came up at 6x12. well going back pages of memory that I'm not going to dig back thru, the timber size was for a truss with no webwork, the top chords spanning 18'. The web members support the top chord so its size can be reduced structurally, but nothing wrong with being larger than structurally necessary if it looks good to your eye.
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Offline Tam Barron

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Re: Clear Span Roof Truss Calculator
« Reply #123 on: August 31, 2019, 06:42:05 PM »
Sorry, I was geeking out, pinned is a non rigid connection that is free to rotate, it can be a bolt, nail, screw, steel pin, wooden peg. To keep the confusion rolling, those are all referred to as dowel type connectors. Ideally a truss would be pinned in that the connections are restrained in space but free to rotate. I think I'm probably deep in the land of navel staring there :D. My point was think of the prying action of the bolts on the wood as the truss is loaded, you don't want them to cause it to split down the grain.

Back in the real world. Here's a scan from "Design of Building Trusses" I think this short excerpt would be considered fair use in light of our discussion. If you hit ctrl and scroll your mouse wheel it should zoom and be readable, that's how I'm reading your pics. I'll post this one and dig in another manual for something I think I remember there that might be pertinent.

(Image hidden from quote, click to view.)<br
Next page;
...steel members.
4. Maximum diameter of bolts <1/4 width of wood and <1/3 width of steel plates. (they mean total of all the bolts in that section of the member, in other words don't compromise more than 1/4 of the net section. Another caveat don't use a bolt larger than 1" dia in wood, chances are you are outside of the wood's strength)
5. A minimum of 2 bolts should be used in each member at a joint.
Ok 
First thing is the span of the roof.
Edge to edge. Anything under 5metres  can easily be done with straight timbers, given good footings.
In reasonable conditions 8inch coach bolts, well greased work well.
Use the old square of the hypotenuse equal to the sum of the squares for the other 2 sides. 
A pitched roof needs an apex beam. DO NOT cut into that.cut notches into your side timbers ( I wish I knew the USA words)
Brace timbers may be needed, but depending on span  are usually used for spreading the load of roofing material.
To stop your walls falling outwards!
A proper structural engineer can tell you. But if you are just putting up light stuff, no probs. Thatch, terracota tiles or slate, put in roof brace
I have used coach bolts, but I think proper wood pegs would be better. Metal sweats, does not expand and contract like wood. 
Any way I have 2 wooden barns about 100yos old and still fine. The one I put up 10 years ago is ruddy awful pine and anything exposed to weather just rots!

Help. ta,I am trying to get used sump oil,the old way of doing things.



Offline Tam Barron

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Re: Clear Span Roof Truss Calculator
« Reply #124 on: August 31, 2019, 06:52:05 PM »
That is the truth of it, every person is an individual, so I've dealt with... am dealing with, all kinds. I'll obey Mama's rules and hush there :D. Engineers, like contractors, are licensed at the state level. The local guys I like here are only licensed in my state, well one goes down into Carolina as well, but they aren't licensed out there. Many folks here use Firetower for timberframe work, they do work nationwide or at least substantially so, I imagine they could take care of you or would know someone. I've spoken with those guys a few times and they are very knowledgeable, a fair amount of what I've been pontificating here comes from listening to them.

If you are pretty well settled on a basic design, then it is time to retain an engineer and have it detailed. At that point I do not drive the bus, I listen, maybe redirect, my design might end up not being the best way to go, it is still just an idea. The good ones give me the closest to what I want while satisfying the laws of nature. As coach Hilton said while getting ready to give us driver's ed,"Now boys, there's some laws that a man cannot break, two vehicles cannot occupy the same place at the same time" He later jammed his brake when I punched it at a yellow light, we slid to a halt a little abruptly and sorta sideways "We stop for those things :D" That's the kind of thing the engineer is checking for while giving me the hottest car he can.


Oh I do so like that! Thanks made me smile!

Offline Sedgehammer

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Re: Clear Span Roof Truss Calculator
« Reply #125 on: October 22, 2019, 08:18:42 AM »
Check out fig 4-25 here;
https://docplayer.net/22941914-Heavy-timber-frame-construction.html

When we came up at 6x12. well going back pages of memory that I'm not going to dig back thru, the timber size was for a truss with no webwork, the top chords spanning 18'. The web members support the top chord so its size can be reduced structurally, but nothing wrong with being larger than structurally necessary if it looks good to your eye.
Working w/ Ben and Griff from Fire tower. Good guys. Thanks for the di rection!
6 x 12 w/ web braces are fine
12 x 12 w/ out
Leaning towards 12 x 12 for a cleaner look

Offline Sedgehammer

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Re: Clear Span Roof Truss Calculator
« Reply #126 on: October 23, 2019, 09:23:11 AM »
 

 

 

 



Here's where we are at

Offline cib

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Re: Clear Span Roof Truss Calculator
« Reply #127 on: October 23, 2019, 10:20:22 PM »

Removed comment. I don't want to derail the thread.

Offline Don P

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Re: Clear Span Roof Truss Calculator
« Reply #128 on: October 24, 2019, 08:40:39 PM »
cib, normally I'm the worlds worst about jumping off topic in a thread, but, I think repost this on the barn thread you started a week or so ago and lets put the evolution of your design there, I think it'll go to more than one Q&A round before you are done.

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Re: Clear Span Roof Truss Calculator
« Reply #129 on: October 24, 2019, 10:28:39 PM »
Removed the comment. I don't want to derail the thread. I was thinking this was more of a general question thread than a specific. Sorry for the mix up.

Offline Sedgehammer

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Re: Clear Span Roof Truss Calculator
« Reply #130 on: October 28, 2019, 07:36:54 PM »
Update. 

6 x12s are fine without bracing. Griff had one truss in his calculations instead of 3. 

I do have question though. If one was to use 3 x 12s 24" OC, how big would the ridge beam need to be you figure?

Offline Don P

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Re: Clear Span Roof Truss Calculator
« Reply #131 on: October 28, 2019, 11:30:19 PM »
I am interested in seeing what you and they come up with. I also think it would be inappropriate for us to begin walking you down the path of reworking a design you all have been, and are, working on.  I do want to see it evolve, it is different and cool. I was downright intrigued by the post tie connection details y'all came up with in the last post, that took a few head scratches to figure out :).
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Re: Clear Span Roof Truss Calculator
« Reply #132 on: October 29, 2019, 12:24:34 AM »
I am interested in seeing what you and they come up with. I also think it would be inappropriate for us to begin walking you down the path of reworking a design you all have been, and are, working on.  I do want to see it evolve, it is different and cool. I was downright intrigued by the post tie connection details y'all came up with in the last post, that took a few head scratches to figure out :).
What I posted is what I had my brother draw up and they said it passes loads. Nothing need be changed thus far, but they have asked me have the architect place it in the room just to be sure.

Reason I asked the on the a ridge beam is I want to compare costs. we're gonna have a fair amount of money stuck in the metal/work alone and I just want to make sure we're in the same county as the ball park....... 

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Re: Clear Span Roof Truss Calculator
« Reply #133 on: October 29, 2019, 10:59:32 AM »
here's a link Ridge Beam from another thread on ridge beams of SYP. I would think DF would even have better loads, but if this link provides what I was asking about, what size would it need to be based on 36' ft width and a 14' clear span? Would one use 20 psf dead load and 20 psf live load?  

Offline Don P

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Re: Clear Span Roof Truss Calculator
« Reply #134 on: October 29, 2019, 04:58:08 PM »
That table works for SYP 2x's built up into a beam.
For dougfir 2-4" thick use the dimensional simple beam calc in the toolbox here, if 5x or thicker material use the heavy timber drop down calc.

Scroll back and you'll find the design loads we were using before, It is probably noted on the prelims you are getting from Firetower as well.

For load on the calc, the ridgebeam is carrying half the roof width, 18'. The tributary area bearing on the ridge is 18' x14'=252 sf x 40 psf (if that is the design load) =10080 lbs
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Re: Clear Span Roof Truss Calculator
« Reply #135 on: October 29, 2019, 06:16:50 PM »
That table works for SYP 2x's built up into a beam.
For dougfir 2-4" thick use the dimensional simple beam calc in the toolbox here, if 5x or thicker material use the heavy timber drop down calc.

Scroll back and you'll find the design loads we were using before, It is probably noted on the prelims you are getting from Firetower as well.

For load on the calc, the ridgebeam is carrying half the roof width, 18'. The tributary area bearing on the ridge is 18' x14'=252 sf x 40 psf (if that is the design load) =10080 lbs
no prelims from Ben or Griff yet, but I just emailed Griff and he just answered.
Roof Dead Load = 20psf
Roof Live Load = 20psf
Roof Snow Load = 10psf
So that adds up to 50 psf rather than 40 psf? If so, 252 sf x 50 psf = 12,600

On the DF grade, what's B+S & P+T?

the beam calculator is asking for total and dead loads. We used 20 psf live load and 10 psf dead load, which you said equaled 30 psf total load. You are using 40 psf now, which is fine, but what should go in both boxes?

Offline Don P

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Re: Clear Span Roof Truss Calculator
« Reply #136 on: October 29, 2019, 08:02:37 PM »
Total load is 40 or 50 psf. Live load is never less than 20 psf (wind). Generally if you have design wind load the snow is gone, but, it could be unbalanced collecting on the lee side, this is what the engineers are for.
Dead load is 20 psf
P&T is posts and timbers, roughly square timbers, within 2" on each face
B&S is beams and stringers, rectangular sections, probably what you are using. 
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Re: Clear Span Roof Truss Calculator
« Reply #137 on: October 30, 2019, 09:22:59 AM »
thanks!
6 x 16 passes, would likely go with a 8 x 16 though. I'll price this out. 

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Re: Clear Span Roof Truss Calculator
« Reply #138 on: November 10, 2019, 07:23:23 PM »
I am interested in seeing what you and they come up with. I also think it would be inappropriate for us to begin walking you down the path of reworking a design you all have been, and are, working on.  I do want to see it evolve, it is different and cool. I was downright intrigued by the post tie connection details y'all came up with in the last post, that took a few head scratches to figure out :).
Ben's calling me in a lil'bit. He want's to scrap the 3 trusses and go with 2 parallel timbered beams spanning the short way about 10' apart sitting on big timbered posts and then use rafters set on top. Do you know if one can still buy the laminated ceiling/roof decking like your pa used in those beautiful houses he built? thanks

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Re: Clear Span Roof Truss Calculator
« Reply #139 on: November 10, 2019, 08:34:31 PM »
I'm right certain he was Solomon's temple engineer, if anyone knows of a supplier it's him.
This is a list of the glulam listed manufacturers, each does a different range of products;
https://aitc-glulam.org/index.php/manufacturers/
This is one that is relatively close to you, I've linked to their timber decking page,
http://www.glulamstructuralwood.com/products/Disdero.pdf
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