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Beginner 24x40 in Southern Vermont

Started by Lennyzx11, August 05, 2022, 01:09:32 PM

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Lennyzx11

5Aug2022 Introduction.
Hi everyone. I'm about to begin my solo build of a 24x40 Pavilion/Carport and would like to chronicle the build and ask for questions/comments here. I am a beginner, worked with construction and remodeling a lot of my 59 years and this is something I've been wanting to do for a long time. Also built a couple of wooden boats when I was into that.
But never a TimberFrame.
My wife rolled over in bed a couple of nights ago, grumbled because of the Iphone's light waking here at 2 am and asked, "What are you doing?" Not very nicely either I must say.
"Learning about Podgers and Prickers." I told her. Her response was definitely not very nice to that either.
So if you all don't mind, Since it doesn't appear that she shares my enthusiam in this new endeavor, I'll continue reading all the back topics, following Youtube related content, and generally go the long way about building my first Timberframe boring you with the incessant questions.
Lenny Dickson in Bennington Vermont
Southwest corner of Vermont

Lennyzx11

5AUG2022 Plans and Foundation

My plans are purchased from Timberframe HQ. I'll follow them pretty closely but do have a few changes I wanted to ask the group if that's realistic or not.


I hired a local guy to do the concrete work. I wanted a quality foundation and Vermont has a code requirement of 5 ft frost walls and I wanted to build into a slope as a continuation of my 24x24 shop. A little more than I could get done by myself without concrete tooling (and knowledge). 

 

 
Southwest corner of Vermont

Lennyzx11

5AUG2022 Chain Mortiser ?

After reading through the past posts regarding Chain mortisers, I think I want one.
Leaning towards the Makita due to the following on here. 
Any recommendations on where to order one rather than just sending off for one through Amazon?
I try to support forum sponsors and "good people" rather than corporations as much as I can.
Thank you,
Lenny
Southwest corner of Vermont

Jim_Rogers

I got mine through TimberWolf tools, years ago.
I don't know how their price compares to Amazon. But they are the guys to go to for parts, such as chains, and such.

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

Don P

After staring at the perspective with my head sideways  :D, are the common rafters big enough, or can they be made big enough to allow sliding the purlin uphill to over the web member? is the web already splayed to a 45? That eccentric loading is not great, especially in snow country.

Lennyzx11

Quote from: Don P on August 05, 2022, 10:16:34 PM
After staring at the perspective with my head sideways  :D, are the common rafters big enough, or can they be made big enough to allow sliding the purlin uphill to over the web member? is the web already splayed to a 45? That eccentric loading is not great, especially in snow country.
Sorry about that Don. Here's it turned correctly hopefully.


 

First question. My local yard is wanting to sell me Eastern White Pine. I want to stay with a clear span inside. With a 40 psf load required. I'm having trouble working through the calculations if the 8x10 in the plans would pass vs Douglas fir. If it won't pass, I may need to go to LVLs or Glulams in those tie beams from front to back (24' span)
It will also have braces at each end.
The outer walls will have a center post.
Can you help me work my way through what size of EWP if it is even available?
8:12 pitch, metal roof with no sheathing and no storage planned. 40 psf snow load per code.
Thank you,
Lenny
Southwest corner of Vermont

Don P

That generates more plan questions. That is copyright and we are diving into his plans, might want to ask first. That appears to be 4 kingpost trusses supporting the ridge and purlins. If so the tie is simply a tension element, a cable. There should be no bending load on it. Can you post detail pics of the heel joint, the tie to post joint, and the top of kingpost joint? I'm assuming the bent spacing is ~13'?

Lennyzx11

Quote from: Don P on August 10, 2022, 10:57:27 AM
That generates more plan questions. That is copyright and we are diving into his plans, might want to ask first. That appears to be 4 kingpost trusses supporting the ridge and purlins. If so the tie is simply a tension element, a cable. There should be no bending load on it. Can you post detail pics of the heel joint, the tie to post joint, and the top of kingpost joint? I'm assuming the bent spacing is ~13'?
Thank you for the help Don.
Disclaimer. These plans are copyrighted by Timberframe HQ and pictures are NOT engineered or permission given to be used for building. Only posted to further my knowledge of my particular set for my education and clarification as I work alone.
Lenny
Common Rafter


 
King Post


 
Right End Bottom Chord


 
Southwest corner of Vermont

Jim_Rogers

The issue I have with TFHQ plans, and I have talked to them about it, is that all their braces and tenons are centered on the timbers with centered tenons.

You have to understand that these designers are used to working with timbers that have been planned on all four sides are true to size with perfect 90° corners.

When we work with our rough sawn timbers these joints are somewhat harder to layout and cut. This is what I discussed with them. And that their plans should be tailored more for rough sawn timbers. Their reply was that they did a survey of customer wants and this is what they feel their customer base wants.

Jim Rogers

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

Don P

I've got fewer problems with putting a mortise in the center of a timber than on an edge.

On this, it is designed as a truss, so the bottom chord is really just acting as a tension element. The kingpost is also simply a rope dangled from the peak, lashed to the center of the tie to hold it up from sagging. The web members are compression members, posts. They launch from the dangling king rod and support underneath the top chord, dividing its span into 2 shorter spans. Point loads from above should be placed over those web members.

The detailing looks kinda lightweight. Find the guild's series on trusses online and read the one on kingpost trusses... uhh now I need to, its been awhile.

Lennyzx11

@Jim, I was kinda wondering about that centered tenon as I have been learning why it's offset by those of you in the trade and understood the reasons.

@Don, that was one of my worries if I changed to EWP. I didn't see the structural support there.
My "kinda" wish was to convert to Queen post for a bit of attic storage, Be able to span 24 ft, and clear that loft door with the top of the tie(s).
I bought this set so I could have something to learn how the "experts" did it.

Going to be close though. The bottom of that loft door is 111" from floor. So that means a top plate/Rafter tie and posts tall enough to drive under all have to fit.

Lenny
Southwest corner of Vermont

Lennyzx11

So I've read some past posts. And am trying to figure out if the 24' span in EWP can be done.

I plugged numbers into the beam span formula as such but I can't figure out where to go from there.

24' span (I didn't figure any braces into the equation yet) times 12' Bent Spacing = 288 Square feet.
It also seems like some of the load would be placed on the ridge beam or top/plate(s) to the posts also but I'm not sure.

40 psf snow load times 288 sf = 11250 = total loads

I then looked up the figures in the wood tables for EWP and got this
875 for Fiber
1.1 (million) for elasticity
125 psi for shear.

The bottom of the table(s) did populate but I'm unsure what to do next to see if it works with an 8x8 beam or 8x10, etc.
Point me in the right direction to continue working it out?
Thank you,
Lenny
Southwest corner of Vermont

Don P

A truss is a different animal than a beam that is simply in bending. A "pure" truss is carrying the load axially along the timbers, that is, the members of the truss are acting as columns and cables rather than as beams. With a roof load on the top chord of this truss the situation is a bit more complex, we have what the old engineers called a beam-column, now it is called a member in combined loading.

So, it takes a different set of equations to figure out the stresses in the members and to check the combined interaction effect of axial loading with bending. An easy way to think about the forces going on in the top chord... imagine standing a yardstick up and pushing down on the end. It will fail by buckling sideways. That is an axial, or column, load. Now, with some column load reach down and push sideways on the stick, a bending load. You are making it want to buckle even more so you must reduce the column load to account for and safely interact with the bending load. It is a dance, the more column capacity used the less bending capacity is available and vice versa.

If I didn't lose you this is a kingpost calc, it is not slick or maybe even gibberish;
Untitled (forestryforum.com)
For design values  for #2 EWP heavy timber use Fb=575, E=.9, Fv=125, Emin=.330

Use the entire span+ overhangs x bent spacing x (LL+DL) to get the total load.

Start there, redirect wherever or if I lost you

Lennyzx11

Quote from: Don P on August 23, 2022, 05:57:18 AM
A truss is a different animal than a beam that is simply in bending. A "pure" truss is carrying the load axially along the timbers, that is, the members of the truss are acting as columns and cables rather than as beams. With a roof load on the top chord of this truss the situation is a bit more complex, we have what the old engineers called a beam-column, now it is called a member in combined loading.

So, it takes a different set of equations to figure out the stresses in the members and to check the combined interaction effect of axial loading with bending. An easy way to think about the forces going on in the top chord... imagine standing a yardstick up and pushing down on the end. It will fail by buckling sideways. That is an axial, or column, load. Now, with some column load reach down and push sideways on the stick, a bending load. You are making it want to buckle even more so you must reduce the column load to account for and safely interact with the bending load. It is a dance, the more column capacity used the less bending capacity is available and vice versa.

If I didn't lose you this is a kingpost calc, it is not slick or maybe even gibberish;
Untitled (forestryforum.com)
For design values  for #2 EWP heavy timber use Fb=575, E=.9, Fv=125, Emin=.330

Use the entire span+ overhangs x bent spacing x (LL+DL) to get the total load.

Start there, redirect wherever or if I I lost you
I had an answer type out in detail but i guess my log in timed out and I lost it.
I assumed the dead load should be the timber weights of each truss? It worked out to 870 lbs or so.
The total load per bent worked out to 1867110.04 which is a large number to me but I don't have any comparison to judge.
Lenny
Southwest corner of Vermont

Don P

Typically designers use either 10 or 15 lbs per square foot for dead load. Live load will be your local design snow load, 40 psf.

To run an example I'll go quick and dirty, you'll need to substitute good numbers.
The load on a truss goes from halfway to one truss on each side, so the tributary width is around 12'. The trib length is the overall length of the truss, I'm guessing 28'. 12x28=336 square feet of area tributary to the truss.

we determined the total load (DL + LL)=50 psf
336 square feet x 50 ponds per square foot=16800 lbs total load on each central truss.

I'm gonna go dive under the truck and try not to melt a post off the battery this time  :D. I'll check on you in a bit.

Lennyzx11

Quote from: Don P on August 23, 2022, 12:45:28 PM
Typically designers use either 10 or 15 lbs per square foot for dead load. Live load will be your local design snow load, 40 psf.

To run an example I'll go quick and dirty, you'll need to substitute good numbers.
The load on a truss goes from halfway to one truss on each side, so the tributary width is around 12'. The trib length is the overall length of the truss, I'm guessing 28'. 12x28=336 square feet of area tributary to the truss.

we determined the total load (DL + LL)=50 psf
336 square feet x 50 ponds per square foot=16800 lbs total load on each central truss.

I'm gonna go dive under the truck and try not to melt a post off the battery this time  :D. I'll check on you in a bit.
I managed to explode a battery in my face long ago. Wasn't fun.
So by plugging in 16800 lbs total load into your worksheet, I came up that a 10.3 depth and 8" wide would pass. OR a 8.5 wide by 10 depth.
I'm inclined to use the 8" wide to match the 8x8 posts. have the mill cut them at 10.5 or 11" in depth.
Would I lose or gain something if I used a splined splice at the king post rather than a continuous beam for the top chord?
Or used a queen post configuration instead?
Southwest corner of Vermont

Lennyzx11

Quote from: Lennyzx11 on August 23, 2022, 03:07:50 PM
Quote from: Don P on August 23, 2022, 12:45:28 PM
Typically designers use either 10 or 15 lbs per square foot for dead load. Live load will be your local design snow load, 40 psf.

To run an example I'll go quick and dirty, you'll need to substitute good numbers.
The load on a truss goes from halfway to one truss on each side, so the tributary width is around 12'. The trib length is the overall length of the truss, I'm guessing 28'. 12x28=336 square feet of area tributary to the truss.

we determined the total load (DL + LL)=50 psf
336 square feet x 50 ponds per square foot=16800 lbs total load on each central truss.

I'm gonna go dive under the truck and try not to melt a post off the battery this time  :D. I'll check on you in a bit.
I managed to explode a battery in my face long ago. Wasn't fun.
So by plugging in 16800 lbs total load into your worksheet, I came up that a 10.3 depth and 8" wide would pass. OR a 8.5 wide by 10 depth.
I'm inclined to use the 8" wide to match the 8x8 posts. have the mill cut them at 10.5 or 11" in depth.
Would I lose or gain something if I used a splined splice at the king post rather than a continuous beam for the top chord?
Or used a queen post configuration instead?
EDIT, I forgot to ask. Am I allowed anything since there will be braces at each end from top chord to post? 
I seem to remember that 1 brace's span could be taken off the span total but not sure.
Southwest corner of Vermont

Jim_Rogers

You maybe using the wrong terms. The top cord is like a rafter, it's on a slope. The bottom cord is like a tie beam, horizontal.
the king post is hung or hanging from the two top cords. And the timber going from the king post up to the top cords are called struts.

The king post holds up the bottom cord.

Now, if you change your design to a queen post truss, then the names are the same accept that there are other timbers in the truss. The timber going between the two queen post is called the straining beam.

Each timber gets its name based on its location in the frame.

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

Lennyzx11

Quote from: Jim_Rogers on August 23, 2022, 04:56:16 PM
You maybe using the wrong terms. The top cord is like a rafter, it's on a slope. The bottom cord is like a tie beam, horizontal.
the king post is hung or hanging from the two top cords. And the timber going from the king post up to the top cords are called struts.

The king post hold up the bottom cord.

Now, if you change your design to a queen post truss, then the names are the same accept that there are other timbers in the truss. The timber going between the two queen post is called the straining beam.

Each timber gets its name based on its location in the frame.

Jim Rogers
You're right Jim. I should have been saying Bottom chord. I knew that. Not the first time I've been called out for not knowing my top from my bottom!
Top chord and Principal Rafter are the same terms?
Southwest corner of Vermont

Jim_Rogers

If you have a common roof rafter system each rafter is small and are usually space out to 16", 18" or 24".
The roof boards (if using boards) run from gable to gable.
If you have a principal roof rafter system each rafter is over a bent. Then there are purlins that run from rafter to rafter.
The roof boards run from ridge to eave.

Principal rafter (I believe) is not part of a truss. Top cord is part of a truss.

Each timber gets its name by the location in the frame.

At the top of this section is a Glossary of Terms. You may need to brush up on those, so we all understand what you are saying.

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

Don P

I'm getting a pass with 8x12 top chords.

Reading down, the bottom chord has 9450 lbs of tension. You can spline through the kingpost, the connection at each end of the spline to the bottom chord members needs to be good for ~10,000 lbs at each end. You will have the same ~5 tons of force trying to shear the end off the bottom chord heeljoint. This is where a steel rod hidden in the top surface of the bottom chord, running from the heel of one top chord member, through the spline hole and grabbing the opposite heel, would probably be the most secure way to restrain that horizontal truss spreading force.

I haven't sized the bottom chord. The size is mostly aesthetic if it is just a tie, the joints are the bear.

Compression at the ridge ~7500 lbs, make sure there is enough surface area to avoid crushing in this and the heeljoint. Now another rabbit hole. You have serious compression forces acting at something between parallel and perpendicular to grain. We have design values published for parallel and perp to grain only. You need allowable compression at some angle between those two. Google "Hankinson Formula" for an explanation on how to interpolate. There was a good section on this joint, I think it was in the commentary to the Guild's design standard.

Web compression is modest

Kingpost tension. The kingpost is pinched between the top chords at its upper end and is dangling down. It has about 2 tons pulling down on it from the bottom chord when the truss is fully loaded. If you are doing a discontinuous bottom chord tabled and splined into the kingpost I would cant the bottom chord members into a very slight arch during construction so when things are settled in and delected the bottom chord isn't seen as sagging. Functionally that would be fine but a smiling bottom chord makes me sad  :D.

The top chord pass/fail and % of strength interaction. The equations behind that are comparing the axial and bending forces and making sure the timber can handle the combination of both loads concurrently.

From there down mostly compression and column stability checks in the compression members. Really whittle thickness or depth down on something and you'll see these start to lose column stability factor, then fail in buckling as members become too slim to avoid buckling.

I better quit rambling and see what you need next. A queenpost truss is going to have a different set of equations modelling its behavior. The numbers and member sizes you generate for a kingpost truss will not really apply to a queenpost truss.

Check bottom chord for heeljoint shear, the red plane. Use Hankinson the check the notch face for localized crushing. Bisect that notch angle, do the crush math once ;);


 

A spline of interlocked black gum is passed through the kingpost and pegged at each side, i think there are 7 pegs on each side of this one. Lower load and 24' span x 10' bent spacing.


 



Lennyzx11

Quote from: Jim_Rogers on August 23, 2022, 07:03:16 PM
If you have a common roof rafter system each rafter is small and are usually space out to 16", 18" or 24".
The roof boards (if using boards) run from gable to gable.
If you have a principal roof rafter system each rafter is over a bent. Then there are purlins that run from rafter to rafter.
The roof boards run from ridge to eave.

Principal rafter (I believe) is not part of a truss. Top cord is part of a truss.

Each timber gets its name by the location in the frame.

At the top of this section is a Glossary of Terms. You may need to brush up on those, so we all understand what you are saying.

Jim Rogers
I was confused. I got this from your link is where I assumed that. I understand now, (I think).
CHORD. In a truss, the major uppermost member (top chord) or lowermost member (bottom chord). In a roof truss, the principal rafters serve as top chords, the tie beam as bottom chord.

My plans show a "Principal Rafter" as the top of each Bent and "Common rafters" spaced out over those for the roof. 
Thank you for referring me to the glossary of terms. More good reading that I missed when I first joined.
Lenny
Southwest corner of Vermont

Lennyzx11

Quote from: Don P on August 23, 2022, 10:58:58 PM
I'm getting a pass with 8x12 top chords.

Reading down, the bottom chord has 9450 lbs of tension. You can spline through the kingpost, the connection at each end of the spline to the bottom chord members needs to be good for ~10,000 lbs at each end. You will have the same ~5 tons of force trying to shear the end off the bottom chord heeljoint. This is where a steel rod hidden in the top surface of the bottom chord, running from the heel of one top chord member, through the spline hole and grabbing the opposite heel, would probably be the most secure way to restrain that horizontal truss spreading force.

I haven't sized the bottom chord. The size is mostly aesthetic if it is just a tie, the joints are the bear.

Compression at the ridge ~7500 lbs, make sure there is enough surface area to avoid crushing in this and the heeljoint. Now another rabbit hole. You have serious compression forces acting at something between parallel and perpendicular to grain. We have design values published for parallel and perp to grain only. You need allowable compression at some angle between those two. Google "Hankinson Formula" for an explanation on how to interpolate. There was a good section on this joint, I think it was in the commentary to the Guild's design standard.

Web compression is modest

Kingpost tension. The kingpost is pinched between the top chords at its upper end and is dangling down. It has about 2 tons pulling down on it from the bottom chord when the truss is fully loaded. If you are doing a discontinuous bottom chord tabled and splined into the kingpost I would cant the bottom chord members into a very slight arch during construction so when things are settled in and delected the bottom chord isn't seen as sagging. Functionally that would be fine but a smiling bottom chord makes me sad  :D.

The top chord pass/fail and % of strength interaction. The equations behind that are comparing the axial and bending forces and making sure the timber can handle the combination of both loads concurrently.

From there down mostly compression and column stability checks in the compression members. Really whittle thickness or depth down on something and you'll see these start to lose column stability factor, then fail in buckling as members become too slim to avoid buckling.

I better quit rambling and see what you need next. A queenpost truss is going to have a different set of equations modelling its behavior. The numbers and member sizes you generate for a kingpost truss will not really apply to a queenpost truss.

Don, Can I convert this Kingpost design to a queenpost relatively easily without losing strength and still matching the dimensional outer measurements?


 
Southwest corner of Vermont

Don P

Yes, you can build a 24' gueenpost truss that is equally strong.

Lennyzx11

Quote from: Don P on September 19, 2022, 07:41:12 PM
Yes, you can build a 24' gueenpost truss that is equally strong.
I've started working on the redesign of the truss. Same outer dimensions leaves a Rafter length of roughly 15 ft. 
I've been reading through the past posts to gather as much "rules of thumb" and I have Chappels "Timber Framers Workshop" I've been studying.
So I plan on the collar tie at the 1/3  from the top with a purlin located there also. And then queen posts located under the collar tie with a purlin located there. Since these are roughly 5 ft apart so I believe more will be needed to support a tin roof/common rafters 9/12 roof. So I'm thinking purlins with a 24" spacing.
Also struts from the bottom of each queen post to the common rafter having a 53 degree angle at the strut lower and 90 at the top strut to principal rafter with another purlin located there. 
Should the purlin(s) be located above or below the tie in points for the collar tie & the queen posts as best practice to avoid too much cutting of the Principal rafters in one area? If so, 8" between like the post to tie beam advice given elsewhere?
Thank you for the help!
BTW, I've gathered up a Witherby 2" chisel, a Barr 1 1/2" and an unknown corner chisel that appears to have an M on it faintly. 
Power tools added to the regular construction stuff include a Linear link Skil 77 worm drive saw, a Mag77 worm saw, and the latest... A Makita 7401L chain Mortiser in like new shape! All found through Marketplace and Craigslist.
Ordered the two center 24' tie beams and the 8x8 posts at the local mill. 
Getting closer to the big start!
Southwest corner of Vermont

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