The Forestry Forum is sponsored in part by:

TURBOSAWMILL GIANT SALE ON NOW UNTIL OCTOBER 31st


Forestry Forum
Sponsored by:


TimberKing Sawmills



Toll Free 1-800-582-0470

LogRite Tools



Norwood Industries Inc.


Sawmill & Woodlot Magazine



Your source for Portable Sawmills, Edgers, Resaws, Sharpeners, Setters, Bandsaw Blades and Sawmill Parts

EZ Boardwalk Sawmills. More Saw For Less Money!

STIHLDealers.com sponsored by Northeast STIHL


Woodland Sawmills

Peterson Swingmills

 KASCO SharpTech WoodMaxx Blades

Turbosawmill

Sawmill Exchange

BRUTE FORCE Authorized Dealer

Woodshax Outdoor Vending Solutions

FARMA


Council Tool

Baker Products

ECHO-Bearcat



Author Topic: help sizing timbers  (Read 900 times)

0 Members and 1 Guest are viewing this topic.

Offline keyote

  • member
  • *
  • Posts: 8
  • I'm new!
    • Share Post
help sizing timbers
« on: May 27, 2018, 05:50:45 PM »
Been out of milling quite a while about to get in again now retired and really set it up right. Id like to build a saw shop/shed. Obviously Id like to make it a timber frame or at least made of timbers.The thing is I have a plan to set up with instead of a 24 extension using a second older saw as a rear extension, which will also have the boards to be edged pushed back onto. I also have this idea of having trolleys that run on pipe track on both sides of the saw, which will continue past the end of the saw into the yard, and in the other direction into the second bay of this building which will be a solar/wood kiln and  lumber storage. very ambitious I know but its actually just the  first stage of finally  setting up my homestead 140 acres remote north idaho the way i always wanted. and the barn shop complex i plan will need a lot of 45 or better beams among a ton of other wood.fortunately i have plenty of trees.

The problem is i want the side of both the saw section and kiln section to be completely open on the side, 50' post centers so i can roll in  50 logs if need be or unload the kiln. think Ill build a log feeder right into the shed and sewt my excavator there as a grapple loaader when needed.

To get a 7/12 pitch and have at least 7 on the back wall of the shed style structure, the front post will be about 20'.tall. I been in heavy construction my whole life so Ill figure it out I always do.Ill probably get an engineer once i determine how to build but want to determine if i can even use wood at all for now or if i need to lower my expectations.
 So in case its not clear its a shed style roof, double building so the front has only the three posts the center post dividing the two 50' buildings the back can have more posts. Since i dont need full height  clear really just enough to roll logs in,with those tall posts thought i could have 45 degree diagonal braces that go out five feet to support the ridge beam. Im hoping that makes my span calculation 40 feet rather than the full 50. I also want 24 inside and since i expect the posts will be about 12x12 thats 26' footprint and 28' with eaves the rafter lengths will be about 32. I found the timber calculator on here thanks looks awesome, whish id found it a long time ago on other projects. But am having some trouble figuring it out, mostly because its a shed design so only one side of the "ridge" has rafters and all the calculations im learning use measurements on both sides of the ridge to calculate tributary width.so here are my questions i guess.
seems I need to first size my rafters so i can know their weight for the ridge beam calculation, but they too have the tributary issue only differently. from what i read Im calculating the dead load over the actual roof square footage so eave to eave times the weight of the materials in the areas between two beams.I set that aside then I need my live or snow load.and that get adjusted by the tributary factor? Yeah im stuck here, i think  when i get to the ridge beam tributary factor its going to  help me allocate weight to  front ridge and back wall, but not sure what im doing here with it and whether i use 1/4 of the beam or if i double it even though theres only  rafters one side?

 I need to  understand this to be able to play around with that calculator. because my snow loads uncertain. Im way way way way up in the mountains end of the national forest my land goes way up one mountain down to a river and then up another Im putting the mill down  in the valley  near the road but its still about 4200' snow loads in town seem to use 70psf but im 2200 feet higher and farther north the university has an interactive map that will give me  ground snow load and i read some where 70% of ground is about right for roof load. but that map says i have somewhere between 560 and 360 pounds of ground load so that 250-350 roof load LOL. Yeah. Experience tells me metal roof at 12/12 work fine but that puts my front posts insanely tall, i read snows angle of repose is about 6-7/12 so figure that would be ok if it built stout. I used 2x12 on my log cabin 30 years ago and a piece of ground i bought out has a cabin with scrap 2x4 rafters lol but its about a 16/12 just got to make sure the snow cnt pile up behind the house so im building to shed off the creek bank.
any help appreciated   

Offline Don P

  • Senior Member x2
  • *****
  • Posts: 4791
  • Location: Southwestern VA
  • Gender: Male
    • Share Post
    • Calculator Index
Re: help sizing timbers
« Reply #1 on: May 27, 2018, 07:18:26 PM »
Don't reduce span for braces. The 50' sounded like way more than a stretch before you mentioned your snow load but hey have fun with the calc.

Trib load is just a fancy pants term, understand it in common sense terms, What you are looking for is the amount of load the supporting beam will carry. If there are two load bearing elements, a beam and a wall here, then each is carrying half of the rafter span that is between them... 26'/2=13' then add whatever is outboard of the beam in question, looks like a 1' overhang so trib width is 14'. Trib area is 14'x50'=700sf. Trib load is 700sf x (snow+dead load)

I have my doubt but you might see if you can do it with winter props... problem is when you forget to put them in before a storm.

Rotate the roof 90 degrees? See if you can even get a 50' rafter to work with a 50' span and 2' trib width... 100' trib area. Then start thinking trusses or a trussed beam.

Offline keyote

  • member
  • *
  • Posts: 8
  • I'm new!
    • Share Post
Re: help sizing timbers
« Reply #2 on: May 27, 2018, 08:10:59 PM »
Thanks I'm not sure how to  judge that snow load  i just never see snow able to stay on a metal roof long so think using the normal 70 snow will be fine. i have huge doug fir so thought maybe a 12x 18 or even bigger would get me my open front.  

Online D L Bahler

  • Senior Member
  • ****
  • Posts: 557
  • Age: 2014
  • Location: Central Indiana - Berner Mitteland
  • Gender: Male
  • Hopp Schwyz!
    • Share Post
    • Traditional Swiss Carpentry
Re: help sizing timbers
« Reply #3 on: May 28, 2018, 10:35:38 AM »
If you need a 50' clear span made of wood, you are going to need to make a truss of some sort snow load or not. 

A simple parallel truss is typical in this sort of situation, and were it me I'd strap the thing with steel just to be sure. 

Offline keyote

  • member
  • *
  • Posts: 8
  • I'm new!
    • Share Post
Re: help sizing timbers
« Reply #4 on: May 28, 2018, 11:51:15 AM »
Think you're right, if i'm going to use a wood  simple beam now i think of it would need to be like 36-48  tall or something. I have an old railroad car that i used for a bridge across  one of my creeks when i was logging that 40, that i dont use for that anymore, its 80 foot and has had loaded log trucks  across it all day long, i  could cut one of its stringers, but wood construction goes with a sawmill is my thinkin just don't ever want to have to rebuild this or even have my grand kids rebuild it. 
there's ways to make open chord wood trusses with pipe webbing or even plywood webs just not the big timber look i wanted. But a timber frame parallel truss for the ridge i think still wood be monstrous, I suspect its own weight becomes a huge factor. for instance if i wanted to use say something like sheets of ply sandwiched between top and bottom chords of 2x6 maybe with diagonal 2x6 as well that would likely be good but to have open webs timbers even without trad joinery is going to be fighting itself as you increase the size to avoid bolts tearing out the self weights canceling out the gain.the other problem with a truss for a shed roof ridge is uneven loading or rather the  difficulty of distortion of the bottom of the truss, suppose  it could be tied back to the rafters to keep it from distorting. *DanG  the old mills around here mostly all torn down now had the type of beams i wanted but i didn't grab them when i could have 25 years ago.I did grab some stuff to build my first log homes rafters and joist  just rogh 2x12s though 

Offline keyote

  • member
  • *
  • Posts: 8
  • I'm new!
    • Share Post
Re: help sizing timbers
« Reply #5 on: May 28, 2018, 01:43:50 PM »
Hey guy s this looks excellent!!!!!! https://courses.cit.cornell.edu/arch264/calculators/index.html

hes got all; sorts of calculators but best part is theyre not limited to common sizes 

Offline Don P

  • Senior Member x2
  • *****
  • Posts: 4791
  • Location: Southwestern VA
  • Gender: Male
    • Share Post
    • Calculator Index
Re: help sizing timbers
« Reply #6 on: May 28, 2018, 05:18:04 PM »
Wow, that looks impressive, need to check em out 8)

Offline btulloh

  • Senior Member x2
  • *****
  • Posts: 1137
  • Age: 66
  • Location: Midlothian, VA
  • Gender: Male
  • I never met an air conditioner I didn't like
    • Share Post
Re: help sizing timbers
« Reply #7 on: May 28, 2018, 05:29:35 PM »
If you want a 50' opening without any supporting column you could do some sort of suspension arrangement on that side.  It would probably be the first time it was ever done that way.  It would be interesting.
HM126

Offline btulloh

  • Senior Member x2
  • *****
  • Posts: 1137
  • Age: 66
  • Location: Midlothian, VA
  • Gender: Male
  • I never met an air conditioner I didn't like
    • Share Post
Re: help sizing timbers
« Reply #8 on: May 28, 2018, 05:55:40 PM »
Another thought, not as bizarre as the previous one:  Make the high side the open side and use a steel truss.  If you put board and batten over the steel it would still give you the look you're after.

HM126

Offline curved-wood

  • member
  • *
  • Posts: 49
  • Location: lochaber, south-west quebec
  • Gender: Male
    • Share Post
Re: help sizing timbers
« Reply #9 on: May 28, 2018, 06:56:26 PM »

Glulam is another option.  Wood Handbook, Wood as an Engineering Material edited by the USDA (US dep of agriculture ) show some beam for a bridge in wood that spans 155 feet !! So 50 feet it is possible in wood.
Here is the ref : https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.pdf
On page 16-10 and 16-11
By the way a very interesting book to read

Offline Don P

  • Senior Member x2
  • *****
  • Posts: 4791
  • Location: Southwestern VA
  • Gender: Male
    • Share Post
    • Calculator Index
Re: help sizing timbers
« Reply #10 on: May 28, 2018, 08:35:14 PM »
The glulam publications list is here;
http://aitc-glulam.org/capacity.asp

Design values are close to the same as LVL, from memory those are Fb 2800, E 2.0, Fv 280

I like the thinking going on here, basically you are building a bridge.

Offline keyote

  • member
  • *
  • Posts: 8
  • I'm new!
    • Share Post
Re: help sizing timbers
« Reply #11 on: May 28, 2018, 08:55:23 PM »
THanks guys, even glue lams are not strong enough as a simple beam when used in bridges its some sort of a truss design. however once the sawmill is set up i start cutting  for my barn  wich is  45 narrow side and thats really tough for rafters too i thought of using a quonset hut kit for the roof but turns out their  engineering claims are all garbage those things get crushed in the snow all the time. I like those gothic roof barns which can be stick framed but i looked into making gothic arch glue lams myself and think if i can kiln dry the wood i can make 42 'high glulam gothic arch rafters they use the same epoxy resins boat builders use for laminated  keells or hulls and that one of the reasons i want to have the 50'saw capacity also the post and beam  barn and loft joists need those 45 foot beams but not glue lams they will get posts 16. oc

If i have to Ill just  use an I beam but i think a  truss can be designed  i know you can make timber frame and stick frame trusses with that span so my only problem is wanting that roof pitch and the high end to support the  rafters  which means half the roof weights might have to re think the shed style thenm i could use just  truss rafters on wall and shed  to the sides  which i didnt want . could pour a concrete reinforced beam too i guess


Share via delicious Share via digg Share via facebook Share via linkedin Share via pinterest Share via reddit Share via stumble Share via tumblr Share via twitter

xx
Sizing Timbers for 18' x 34'

Started by Rougespear on Timber Framing/Log construction

10 Replies
1603 Views
Last post May 29, 2016, 02:20:16 PM
by Rougespear
xx
Sizing Chart for Timbers

Started by tadkins on Timber Framing/Log construction

10 Replies
2832 Views
Last post February 03, 2014, 02:14:32 PM
by Thehardway
xx
Milling own timbers vs ordering timbers from a sawmill

Started by Joe Vachon on Sawmills and Milling

8 Replies
1141 Views
Last post July 03, 2017, 12:45:18 PM
by thechknhwk
question
Hardwood timbers vs. Softwood timbers

Started by jeremy86 on Timber Framing/Log construction

4 Replies
895 Views
Last post September 23, 2016, 09:01:22 AM
by Heartwood
 


Powered by EzPortal