Hammerbeam general Questions

[beenthere]

I'd suggest keeping the design so the birds don't have a place to nest or hang a nest, if that is at all possible. The mud nesters might still be a problem.

[Don P]

A good point, that blocking could be positive intead of a negative step. One tried to build a nest on an exposed peg on the entry at work. It fell on the porch and made a mess. Our entry is blocked like the pic above and has not had any nesters in its life... dirt daubers and carpenter bees, but no birds. Course I've left many more comfortable places for them around  .

[Jim_Rogers]

I wonder if I wouldn't be better off, moving the struts up to the top 1/3 and adding queen post at the halfway point? Thoughts everyone?

Here is what I got by moving the struts to the point where they'd be 90° from the bottom of the rafter and adding the queen posts to the mid point:



It doesn't look bad, but the struts still don't look right to me. Placed them four inches above the king post to bottom cord connection to help reduce the impact of all that joinery in one spot. If I move them lower it would move them down the rafter some.....

Next you said:

Top plates: I believe in the drawing they would attach and be at the same level as the tie beams, this means we have the tie beam, wall plate and post all tying together in a 6x6 area I don't think an English tying joint would work in that amount of area would it?

You have set a bottom limit to 101 inches for the bottom of the tie beam. If you're going to put in some connecting plates to the house gable then these should be at least 6" lower or raise the height of the tie beam. You really don't want a three way connection at the top of that post, it will weaken it considerably. But if you raise the bottom of the tie beam you'll change the rafter pitch in order to maintain the top of king post location.
Adding a ridge pole to the top back side of the king post shouldn't be a problem with a spline and housing, we can deal with that later. That's the easy one.
The plate connection is one you'll need to decide on next.

Jim Rogers

[petehalsted]

Purlins on top is a Great ideal and eliminates on of my "trouble" joints! And makes it that much easier for me to tie back into the other portion. Only problem is it effects the sizing of the entire bent, so that it will still meet up correctly with the one on the house. It's a little early for my brain, not sure if just shorting the post by the amount of the purlin accomplishs that or not (something in the back of my head says no, but will have to wait for a cup of coffee)

Anti Bird and Dauber design is defintely worthwile. You can't tell it in the photos of the house, but when the windows were originally trimed, it was done with 1x4's on top of the log siding. I am slowing replacing all of that trim by letting in 2x4's instead. Each of my windows with the 1x4's supports at least 2 wasp nest, all thos little openings where the two logs join and is protected by the 1x4 looks like a penthouse to wasp! And did I mention I'm alergic! Live and learn!

Jim, I think that version of the bent looks great, and we address both of the issues from Don's math by moving the struts up, and adding queen post to support the bottom portion of the rafters.

Plates - I could live without them as far as looks go, but to me it seems that I need something from the house to the post, otherwise the only thing keeping the bent standing is attachments on the rafters (purlins, roofing, etc).

We may have another issue if the post in your drawing is 101" and the end of the tie beam is square, that means the roof gable has to stop at 107" not 101" That may be ok, I really got to get the other gable drawn in sketchup so I can run some lines between the two and see what is and isn't meeting up.

So what is everyones thought about the plates or whatever attachment between post and house, as that really has to be known before I finalize sizes.

[petehalsted]

Well I spent some time in sketchup, so I could get higher authority (wife) approval of the general concept so far.

I am struggling with exactly how to lay out the traditional framed portion of the gable so everything comes out right.

But anyway thought I would share a drawing of what I have so far.

[Jim_Rogers]

Looks good to me.
I'd put either a long brace or a shorter brace between the post and the plate going to the house.
You don't want the two brace pockets being at the same elevation in the post.

Jim Rogers

[petehalsted]

After my last post, the coffee finally kicked in. I was attempting to figuring and draw backwards. I was trying to figure out where to place my traditional framing so everything worked out, and was suffering brain cramps. Then it hit me, if I put my roofing material on, then all the framing just references that and everything goes where it needs to.

So here's a new drawing, I haven't drawn the faux bent yet, that why all you see is logs in the rafter area, and haven't figured out how to have 2 sides of an object have different material in sketchup so shingle are on the underside. And of course haven't drawn (figured) out any of the details for attaching the halves but at least I have a good idea of the final product now.

Jim, I will add the braces, wasn't sure if we were sticking with plates or not so I hadn't drawn it yet.

So here's a sketch that sort of looks like what the end result will be.

[Thehardway]

The steep angle of kingpost struts appear as though they will contribute little to the overall strength.  They could in fact weaken the structure by lessening the tension/compression dynamics on the kingpost head and redirecting rafter load to the base.  Is this not correct?

On the other hand if the struts were lowered to intersect rafters at a point closer to the prince posts you would be building a "Howe truss" or "K" truss which is very common lightweight truss design and has a proven design track record.  The loads are well distributed through triangulation.  More pleasing to the eye as well.

[Don P]

I agree.
The queenposts are also putting a bending load into the bottom chord. I don't think its a truss as drawn without a tension member to the initial strut.

I was looking for some good truss pics, this link has a good glossary as well.
http://www.barrettlumber.com/truss2.html

[petehalsted]

In the drawings above you can see where Jim originally drew them to the point your talking about. My concern ( ain't like I know what I'm talking about, just looking at it with untrained eye) was that the angle was so extended, that it looked like any force on the rafter would make the strut act as a lever, pusing down on the rafter end and up on the king post end, and the jointery at the king post would be in tension, and with my 6x6 timbers that tennon would be smallish.

The link Don posted shows a image of a Howe truss and it does look like those struts are at a an angle like mine would be if moved, but again those are stanard trusses and don't have the same issues at the joints that a timber frame has.

So is my thought process wrong?

[Don P]

Whoa, one aspect got better, I cautioned there was more to check.

What a truss is doing is using wood axially loaded where its stronger ... in tension or compression, rather than in bending. A post can take alot more load with the grain than a simply supported beam can bear with the same load. The members between the panel points in a truss are treated as axially loaded posts,(columns loaded along their length or axis) we kinda cheat on the top chord but keep that thinking.

Build it out of popsicle sticks in your mind, simply pinned and free to rotate at each node. Did you build a truss or a mechanism.

I suspect the best location for the strut is midpoint of the rafter. The forces in the rafter are one part of the equation. You also have to look at the length of each member, moving the struts upward makes the lower member of the rafter longer. (Each top chord, or rafter is composed of 2 members. From the peak to the strut, and from the strut to the heel). As the lower member gets longer it becomes weaker.

The kingpost to my knowledge has struts that bisect the rafter into halves.
With the Howe the webs divide the top chord next into equal thirds.

Roughly add a zero to the numbers on the picture to get the internal forces in the truss.
The right side is what we've been calling a kingpost, the top chord is divided in half. The left is a howe truss, the top chord is divided into thirds. The forces within the members don't change all that much, their span does. The time to add a web is usually when a member is getting into buckling trouble.

[Thehardway]

We are mixing up a lot of terms and I think I am getting confused.  Perhaps it would be best to review/define terrms before going further?

Post= vertical member
Rafter= diagonal topmost member
Strut= diagonal support member similar to a brace
Beam= Horizontal member
Kingpost Truss =  Single post disecting into two right triangles.  Post in tension, Rafters in compression, bottom chord in tension. Post suspends from intersection of rafters and supports weight of bottom chord at centerpoint.

Kinpost Truss with Struts = Same as above with addition of struts which extend from base of kingpost and bisect the rafter spans preferrably at midpoint

Kingpost Truss with Struts & Prince Posts = Same as above with addition of secondary posts which bisect bottom chord midway between rafter foot and kingpost joint and intersect with the
Kingpost Struts preferrably at the rafter midpoint.

Queen post truss= Truss with only two posts which extend from bottom chord to the rafters midspan

Howe truss= Same as "Kingpost with Struts and Princeposts"







King post trusses with struts are often misidentified as Queenpost trusses as can be seen in this example:  http://www.rockyridgedesigns.com/truss_styles.htm

Princeposts are often misidentified as queenposts.

King posts are often thought to support rafters from crossbeam.  This is not so.  The kingpost supports the crossbeam from the rafters.
Kingposts depend on the leverage and wedging action of the rafters against them to gain their best strength.
The best trusses distribute weight and stress evenly amongst members with respect to length and stiffness of the members.

[Jim_Rogers]

I don't know if I can agree on the site that was listed as a reference site for terms of truss styles.
The lower picture doesn't show a queen post truss.....

I'll have to do some research on the "Prince post" label and location.

And I'd like to ask you, Thehardway, to list your sources of the definition of "prince post".

Thanks....

[Don P]

Perhaps it would be best to review/define terrms before going further?
Post= vertical member

I think I must have blown this;

What a truss is doing is using wood axially loaded where its stronger ... in tension or compression, rather than in bending. A post can take alot more load with the grain than a simply supported beam can bear with the same load. The members between the panel points in a truss are treated as axially loaded posts,(columns loaded along their length or axis) we kinda cheat on the top chord but keep that thinking.

I said post and should have said column.

When chapter 3 of the NDS (Nat'l Design Specification for Wood Construction) leaves sections 3.2-3.5 on bending members, it begins section 3.6 titled Compression Members.

3.6.1 For purposes of this specification, the term "column" refers to all types of compression members, including members forming parts of trusses or other structural components.

Section 3.8 discusses Tension members, 3.9 "Combined Bending and Axial Loading"
3.6-3.9 use the term column,  work with column stability factors, etc.

The reason I'm driving the point is that this is a different way of using wood than just as a simple beam in bending. You are running the load axially, along the axis of the member, just as in a column. The member can be at any angle, the load is being taken along its length, parallell with the fibers, as in a column.

A truss is assumed to be free to move at every node (the dots on the FEA drawing I posted above, each is a pivot in design). The loads are assumed to be applied to the nodes only. I distributed the roof load among the nodes of the top chord. The loads are then taken through the members along their length,axially. We check the columns for being stout enough not to buckle. The arrangement of the webs reinforces those columns that form the top and bottom chords, keeping the columns stable, reinforcing them before they become too slender for the load they are under.

I think what we've been calling a kingpost truss, is a form of a Howe truss

But no matter, as long as we can follow the conversation, I know 3 names for a nail puller... well, that makes 4  :D.

[Max sawdust]

Pete,
Considering Jim's two piece tie beam?  I used it and liked it very much.     My span was 18'

[Thehardway]

Jim,

Reference for the definition of the term "Princeposts" can be found in:

"Kingpost Truss Engineering, An Addendum by Ed Levin. September 2004, Timber Framing No. 73."  In his assessment of the truss found at Castleton.

Oddly enough the TFGuild glossary does not reference the term nor does Websters online dictionary.  There is, however, a definition of a"Princess posts" which appear to be the Princeposts counterpart in a Queenpost truss.

I was not intending to call anyone out or point out mistakes, just prevent confusion, the term "Queenpost" seems to be overused and oftentimes incorrect as can be seen in the illustrations of websites referenced by both myself and Don P.


I have great respect for Jim and Don P. and meant no harm.

There are three other names for nailpullers ;D

[Don P]

And none taken.  I've thought of one more nailpuller, this'll drive me nuts trying to think of 2 more :D Hope y'all will indulge more rambling 

I went one step further with my train of thinking.
This is a 6/12 kingpost truss with struts at 6/12, so the top chord is braced at midpoint.

I came up with 3020 lbs compression in the bottom part of the top chord (see the 302 on the diagram...x10=3020 lbs compression), I roughly figured it as 85" node to node. The black lines going straight down marked 90 are loads, not princeposts, this is a simple kingpost with struts, a fan, a crowsfoot...  :D


I then took that 3020lbs in the lower top chord member and entered it into a column calc to check it. It looks good and still has 94% of its strength at that length and load.

I swung the struts up to a 45 degree angle and checked again. The compression load in that member is down to 2680 lbs but the length is up to around 113"


This way still looks fine, we,re down to 88% column strength even though we have lowered the load, the increased length has cost some. Notice the max allowable column load is 11,000 lbs at this length and was about 11,800 lbs at the 85" length.


If you notice the FcE value at the bottom of each calc, the critical buckling allowable design stress value is dropping fast as the length increases.

This is oversimplified and doesn't account for the roof being uniformly loaded instead of node loaded but it shows where I was coming from with the extra check not just for compressive stress but also member length and stability.

[Jim_Rogers]

Thehardway:
Thanks for that reference article, I reread it just now.
I would think that as each timber in a frame is labeled based on it's location, that a prince post could be the name of the timber when a king post is present. And when the king post is not present then it could be called a queens post...
But I don't have any reference to this assumption....

Jim Rogers

[petehalsted]

Sorry to abadon the thread for the weekend as you'll see below I was a little busy.

I thought some might like to see a photo of the 1923 barn that where my 6x6's came from. Most of the siding was taken by someone else, all I have are the ones that were to high for them to get to.  It was part of a sorgum (sp?) mill operation in Ellington, MO and interestingly enough was refered to as the "New Barn". I never saw the "Old Barn"  :D



And what I did for the weekend. Got to start paying back the help I got taking down the barn. This is one of my Uncle's buildings in Ellington. Will be several phase throughout the summer taking it from this to a squared front old west looking building. That's my cousin Matt (nearly 20 years younger than me) on the porch, It was the two of us alone that dismattled the entire barn, so as you can imagine I have quite a bit of sweat equity to payback to him.



This is how we finished up this weekend. Not timberframe, but its not hard to see where some of my design influences come from  :D Except fo the post and braces, the wood is all from the barn. Post and braces are from the local pallet mill, of which that portion of MO has plenty to chose from! Didn't get to the bottom rail and we are still debating on what we will do between the two railings. Tossing around faux wagon wheels, or 3 X's in each opening. And it needs the metal roofing, but that's someone else's Job, I'm a woodworker!



Next phase is to remove that God Awful concrete stucco face from the building and reframe with vertical 1x6 siding. Then we move above to put a faux square front on the gable end.

Nothing related to the thread (other than photo of the barn) just want to share my weekend. It's nice seeing parts of the barn begin thier new life.

I will make a second post concerning the actual thread topic.

[petehalsted]

Now on to the topic at hand. :D

First the whole Queen, King, Prince discussion is interesting, and is one of the areas that does serve as confusion for us beging timberframers. In the last month I have read 3 1/2 books on timberframing and the terms do start swarming in your head. It's confusing how the exact same item can sometimes be called something completely different by where it is in the frame. In the end it's nice because it far more describtive than traditional framing, but it does make for alot of terms and some duplication of terms as seen here.

Don,

Thank for for going into greater detail on your graphs. I now understand what I'm looking at. I did think the two inside vertical lines where representing queen/prince post, and I bet I wasn't alone there. And I also finally understand why you were talking about the top cords as columns, that took a while to get through my thick skull.

So all that said, it looks/sounds like Jim's original drawing was right on the money, and my lack of understanding truss dynamic's took us down a road to not only an Uglier bent, but a weaker one. I will redraw the sketch with the struts to the midpoint and remove the queen/prince post. Add bonus is we don't have to figure out what to call them  ;D

Max Sawdust, yes the plan is to use Jim's two piece splined tie beam. Thanks for sharing your photo, it give's me further inspiration to get my project moving. BTW, I don't think I shared it on the thread but did in a email to Jim (when it sent me larger drawings of the spline joint so I could understand it) I have been slowly redoing the trim around the doors and windows, changing from 1x4 on the surface of the logs, to 2x4's let into the logs and I use half laps at the corners with ebony pins, so having the opportunity to use a contrasting wood for the spline lets me tie the entryway design into the house design a little more, although I don't think I will spring for an ebony spline that size, probably will be walnut.

Thanks again everyone for your input and help. Once I get caught up I will update the drawing and then start working out some details on the jointery. Question, since I'm new to the forum, do you all prefer to keep something like this in a long winding thread that lives a long time, or to start a new thread as we move to dicussing the jointery?

[Jim_Rogers]

Pete:
You can keep the joinery for this project going in this thread, it'll make it easier for future readers to find it.
Jim Rogers

[petehalsted]

Didn't get a chance to work on any of the jointery yet. But here is a sketch with the struts returned to midpoint. And also the side braces in place. I made the side braces hit lower on the post to avoid having extra jointery in the same spot of the 6x6 post, but not sure I like the look right now what do you all think about it?

Will try to start on jointery this evening.

[beenthere]

For that exposure of timbers to the weather, I'd put a 3' overhang to limit the times those joints get wet fro rain or snow, and help out the times they can dry out. Maybe you have something else planned to 'cover' that problem. Just a thought that comes to mind. I like the look you are trying to create for your entry.

[Don P]

and Beenthere redoes the math  :D

[petehalsted]

Just an update. Project on hold for a while. I will be traveling pretty extensively for the next 6 months. This month has been crazy trying to get all the honey do items done before then. Once things settle done I hope to have to time to work on the design while sitting around in hotel rooms. Thanks for all the help so far and hope to get back to it soon.