Since this seems to be a popular thing I thought I’d try another.
Since you’re getting so good at this, you’re now reviewing shop drawings BEFORE the trusses are built.
When you flip by the drawing of this girder truss something catches your eye. What is it?
BTW – I think this is a fairly easy one. So would you builders mind laying back a while and letting some of the others take a shot at it?
And a side note to Blue – You’ll notice this drawing has a heel height and bearing elevation on it. (-:
It’s time to change the air in your head.
Replies
You have put different connection plates on the right and left side of the truss implying that the load is unequal on the two sides. I would guess that this implies the right side of the truss (on the drawing) is expected to carry more weight and if it were flipped in the field, it could be problematic.
Steve
I see the unbalanced span condition, even though the truss is symmetrical, as far as the webbing goes.
And, that is why the plating is heavier on the long span side. This is an easy one to put up backwards in the field.
Blue would get it right, though.
We've some trusses to put up in about 8 weeks, with this exact condition. I'm glad you posed this problem, as it is a reminder to us to get the ends correct.
Cantilered? No load point on the left....."If 'tis to be,'twil be done by me."
It would be better to make the bottom chord splice over the load bearing wall.
If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again
"It would be better to make the bottom chord splice over the load bearing wall."
Nope.
Splices are typically done where they work best from a cost/manufacturing standpoint. This is often in the center of the truss. (But only if it doesn't waste lumber) That makes for less saw setups.
The program calculates the bending moment wherever the splice is, and figures the plate size accordingly. So the splice can be located almost anywhere.
There are advantages to being elected President. The day after I was elected, I had my high school grades classified Top Secret. [Ronald Reagan]
Well then, let me go with the orientation and location of the plates on W2.
If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again
"Well then, let me go with the orientation and location of the plates on W2."
Which end of W2?
Either way, that's not the problem
"To Do Is To Be" [Socrates]
"To Be Is To Do" [Plato]
"Do Be Do Be Do" [Sinatra]
Then I'm going to have to go with the obvious, based on my extensive experience...
The problem is that it's not made out of steel. <G>
If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again
it's a cantilever truss and needs a support over the cantilever
"t's a cantilever truss and needs a support over the cantilever"
Not to give you TOO much of a hard time, but -
If it has support at the end of the cantilever, it's not cantilevered.
Or are you saying it should NOT be cantilevered?
Get your facts first, and then you can distort them as much as you please [Mark Twain]
boss , the way it's drawn..
View Image
the 9 ft. on the left is cantilevered.. there are only two support points.... the left side is unsupported.. the bearing point 9' in from the left needs a vertical support in the truss design
Mike Smith Rhode Island : Design / Build / Repair / Restore
"...the bearing point 9' in from the left needs a vertical support in the truss design."
You don't need a vertical, as long as the truss is triangulated.
Q: What is a man's idea of safe sex?
A: A padded headboard.
boss.. my job.. i want a vertical.. pretty please ?
oh, yeah.. and all a dem fancy labels "this side out" "web brace here"
"bearing point here"
and the stamped prints for my building inspector .. and the bracing diagrams for my Liability Insurance
also.. we have to put markers in to show how deep our insulation is..
can you staple labels to the trusses 24" above the bottom chord ? the labels can have an arrow and "24 inches "
you can do a roll-off delivery.. we don't need no stinkin craneMike Smith Rhode Island : Design / Build / Repair / Restore
Boss,
Second guess - Does this have anything to do with where the cantilever point is? I'm no builder (and don't play one on TV), but I thought you could not cantilever more then 1/4 of your total length which would mean that your fulcrum would be at something like 5'8" for a deck with this span. Do cantilevered trusses act the same way?
Steve
BTW - Great idea. It's a fun learning exercise. Thanks for doing this.
I wuz wrong. Looking at the "intermediate" bearing, I missed that it doesn't have a bearing on its left end.
Thus drawn, it's a cantilevered truss. But, as I said about the asymmetrical plating, it is an easy one to erect backward in the field.
Boss, this isn't an easy one!
It's not easy when I don't have an basis of information about the process of designing trusses. All we know how to do is install them and sometimes we get them standing without breaking them!
I've got to go along with the non uniform plate thing.
The fact that the left side bearing wall is not drawn in might mean something.
I don't know about the truss design, but I can tell you what the pine line will be now that the heel is shown.
Assuming that the span of the deck is correct, and there will be a 12" overhang, past brick, using a 1 x 6 fascia and a 1x 6 frieze, I come to the following conclusions:
The top of the fascia is 5.83" below the top plate.
If the soffit material is 3/8" plywood (typical around here), then the bottom of the Frieze is 15.25".
If we are using wood windows, that have a brick mold, the header can be a total of 12.20". I'd use a 2 x12 and add a 1x4 rs spruce filler after the trimmers are installed.
Personally, I'd suggest a higher heel to accomodate a larger amount of insulation.
When my wall framers start the wall, I'd scribble all that information on the deck somewhere near them. We'd all remember that the "pineline" is 15 1/4" and everything would run smooth from there.
Of course, when I saw that 8-0 elevation number, I'd automatically equivocate it to 8 1 1/8" and later if I saw a different height, I'd simply automatically make the 1 1/8" adjustment on each truss in the system.
That's how we do it...all that calculating took me 30 seconds. Without that heel height and elevation height, that same calculation might take me one hour or more.
blue
blue
Just because you can, doesn't mean you should!
Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!
What size are your top and bottom chords?
If we fail to catch a cosmic fish it may be a trillion years before the opportunity comes again
Well I thought I had an answer then looked closer at it and changed my mind.
Looks to me to be in backwards.
That 9' over hang would put a lot of stress on the left side. The plates are smaller on that side then the other.
Dane
I will always be a beginner as I am always learning.
O.K., I think this has gone far enough. On the last one, someone asked me to wait a whiole to let more folks try to figure this one out. So that's why I waited this long.Like most have guessed, the truss isn't plated symmetrically. The webs are symmetrical, but that isn't enough. In my experience, that gives you about a 40% chance of it getting installed correctly. On this particular truss, there is no load applied to the left of the interior bearing. So the 1/4 span rule of thumb doesn't really mean much. I've been trying to come up with other puzzlers, but it's getting more difficult. I'm about out of ideas.
A modest little person, with much to be modest about. [Winston Churchill] (about Clement Atlee)
Boss, just post some of those really hard hip jack, vaulted, stepped up mono hip girder, piggy trusses.
Then we can ask the guys that bad mouth the trusses how they'd frame it with sticks.
Use one of those long spans too, will ya?
blueJust because you can, doesn't mean you should!
Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!