Help me Build a Workshop?

[tsodak]

OK, so I have been playing around with the calculators this morning and things are actually making sense. Your drawings have better more consistent numbers in the than mine (it can be hard to get those nodes placed just right) but the long and short of it is, if I were to build your double fan there out of 4x10, or 6x8 timbers, it would pass the strength test in the top members. When I reran to go to an 8 foot spacing I could build it from 4x12's and they pass, although I think the linkage numbers are going to be more difficult. So to me and with the equipment I have available, that 10/12 roof w/ the double fan makes a lot of sense.  So lets talk more about that.

One thing jumps out at me from a linkage standpoint.  By going with that arrangement, if the bottom member is joined in the middle instead of at the node, do you design the joint for 3800 pounds or 6500??? It seem to me that one of the strengths of that design is that it takes some of the strength bearing responsibility away from that joint and gives it to the compression areas.

IS that crazy???

[Don P]

Think of the double fan as two individual trusses pinned together at the ridge. Remove the 38 bottom member, it starts to slide apart. Throw a rope across the center gap and it will take 3800 lbs of tension to hold the 2 sides together. The 6500 is part of the 35/65/82 truss section.

In a purely tension member I don't see a problem with a splice there. The truss program is assuming all nodes are frictionless pins with each member going from pin to pin. It also assumes the loads are only on the nodes giving the truss just axial forces. In the real world we have continuous top chords and uniform loads that add bending. We do have conditions that are not purely "trusslike". One thing to think about is what happens to a connection when the truss deflects and the nodes need to rotate a little, you don't want to split wood.

I came across this article tonight, its got some good information in it.
http://www.grayengineeringky.com/GlulamTrusses%20Article.pdf

[Radar67]

Don, I've been following this thread and have a few questions. On the picture below, each of the nodes are loaded with 20 (or 200 pounds per), is that correct? The members at the top, with the 2 above them, look odd compared to the other numbers. Does this make since to you? Compared to your other truss runs, does this design (something I am playing with only, not trying to get a working design) look normal? Is there anything that jumps out at you?

[Don P]

That's neat. The 2 load doesn't look odd, most of the tension is following the angled chord "217". What is the span and spacing truss to truss, looks offhand like they must be pretty close  ???

[Radar67]

The span is 20 foot and the spacing is 4 foot. The upper chords are 7/12 and the lower chords are 12/7 pitch.

[Don P]

Stew, my barn is 12/5 with a 5/12 top, I do like the looks of inverting the pitches usually. I just ran a tie across at the upper pitch break.

I was looking around on the AITC website this morning while waiting for the rain to quit. I think I've posted this link before but its a good one. It shows many details and do's and don'ts.
https://www.aitc-glulam.org/shopcart/Pdf/aitc_104_2003.pdf

The cantilever connection is how the glulam folks often deal with a splice off a post, section 3. A moment resisting connection is shown in fig 8.6

Section 5 deals with post to beam connections
Truss plates are shown in section 9

Definitely read from page 27 down, connections to be avoided.

[okie]

I just found this post. I really like the idea of using the pipe in the truss joints, that is really cool. It looks like a straight forward approach and a safe joint given the numbers stated. I just kinda skimmed this as I got to wake for work in about 4 hours but will read it all.
Y'all have a merry christmas.

[woodwright]

"When we build, let us think that we build forever.  Let it not be for the present delight nor for present use alone.  Let it be such work as our descendents will thank us for; and let us think, as we lay stone on stone, that a time is to come when those stones will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them  'See! This our father did for us'"

                                                                                                --John Ruskin
maybe this will help... indigenous builder/timber framer