I’ve talked several times here about bracing trusses and how devastating a truss collapse can be. Here’s an article about just such a situation.
http://www.brunswickme.org/fire/collapse.html
Please think about these pictures next time you’re setting trusses.
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A strick rule with firefighters is "don't trust a truss"
This has nothing to do with fire.
It's about inadequate bracing.
boss.. just based on the news item.. it may have been the collapse of a damaged truss, rather than inadequate bracing...notice that the remaining trusses are still in placeMike Smith Rhode Island : Design / Build / Repair / Restore
You may be right - One truss may have fallen and knocked others over. There isn't enough info in the article to tell exactly what happened.
But the trusses that fell probably weren't well braced, or the impact of one truss wouldn't have knocked them over.
My point in bringing this up again wasn't to argue the specific points of one incident - More as a reminder in general that bracing should be taken seriously. Q: What do you call a couple that uses the rhythm method of birth control?
A: Parents.
B.H. I had 110ft of 60ft 5/12 trusses go down in Springfield . We braced the gable in four places off o continuious rat runs with "w" bracing the rest of the way, the night before . The next morning it looked like bad weather comming and I sent six men up to do some extra bracing just in case. Two were on the ridge and four were working the outside walls and it happened a 60 mph wind came from no where . We agreeed later that we heard truss's breaking before they racked and colapsed with my guys in the middle. In the aftermath it reminded me of a med evac in Nam ,light rain EMT personnel , fire trucks ,police cars and a crowd of on lookers. The six went to two hospitals in our area for treatment , watching your guys get stitched back together with that look in their eyes of "what went wrong" and not being able to answer them was one of the most helpless feelings I' ve ever had. One of my people that was on the ridge said it flashed through his mind that I had said once "if truss"s go try to drop straight down " he did and said he thought it saved him from getting any thing worse than 30 stitches , he was trapped under the truss's for about a 1/2 hour .When truss's go , they stack into a solid "floor" of wood about a foot thick and in this case the red iron at the outside walls held the most of the tails up with the ridge bowing down and complicated things even worse. When we talk about what kind of people we hire , these guys ranged from "old hippie to out of work accountant, three came back the next day and the other three the day after and they did what they thought they should, bandaged and still some bleeding , we went to the other end of the building and started setting truss's. Was it a bad call on my part , yes , could it have been prevented yes, all I had to do was shut it down for a while. could any thing have stopped the truss's from going ,no.
Glad nobody was killed. Is it possible to get one of those hard working scientist to send me the extreemily fascinating documentation on the scientific research project I seen someware in this forum earlyer. Just can't seem to find it now. I wish to analize and convey data to some of my colluegs. [email protected]
B.H. a couple of comments on my previous post . What do you think of "X" bracing from the rat run to the ridge down the center of the buiding , of sheeting the truss's as you set them and what effect does a sheeted gable truss' have with wind load?
Good question, Nails.
Boss, please do take this opportunity to go on at length about bracing -- I'd sure like to hear it.
As a foreman and later as a site super, I've gotten into some tense situations both with employees and subs about how much bracing to put on trusses.
The ususal reply is "You don't need it."
My reply is "I don't care what you think I need, get back up there and install it."
My view is that we are not bracing for good weather with no wind, we're bracing for the freak storm that didn't show up on the weather report.
As a former firefighter / rescue specialist, I will say that almost everyone I ever picked up who was still alive and could talk wanted to tell me how they didn't think "this" (whatever the emergency was) would happen to them.
Anyway, I'd sure like to know how much is enough and how much is a waste of time and material.
Any rules of thumb or general principles to employ?
Thanks,
DRC
"Go on at length, huh ???
Actually, I already have. Here are a few threads about the subject:
http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=21634.1
http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=27573.1
http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=23117.1
http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=27848.1Two fonts walk into a bar.The bartender says: "We don't serve your type here."
Sorry to hear that you had a set go down. Was also sorry to hear that some of your guys were hurt.
I don't remember that one - I've investigated 3 incidents in Springfield, but yours doesn't sound familiar.
About your question on "X" bracing - I prefer to think of it as diagonal bracing. I guess it becomes "X" bracing if you cross 2 pieces of diagonal bracing.
I think diagonal bracing makes a ton of difference, but it has to be done right. It has to start FROM something and go TO something.
For instance - Start the diagonal bracing at a brace that come from the ground up to a wall. Then run your diagonal bracing FROM that brace up TO one of the rat runs on the top chord. This will add a tremendous amount of rigidity to the bracing.
OTOH - Start your diagonal bracing at any old poiint along the wall, and run it to another point on the top chord that's not right at a rat run of bracing, and it will do very little.
Setting a sheathed gable definitely makes things different. I know of one job in Sprinfgield that had sheathed gables and went down. On one end of the building, there were 4 (very long and wobbly) braces that went from the ground up to the 60' sheathed gable. These braces were installed fairly well, although they should have had braces on them due to their long length. (To keep 'em from buckling)
They started setting from the braced gable and went to the other end. Guess they were tired or something, as they didn't put a single ground brace on the sheathed gable. And there was not one single piece of diagonal bracing anywhere on the trusses. (As best as I can remember)
The wind came from the wrong direction that night, and blew over the sheathed gable without ground braces. Since there were no diagonal braces anywhere, it pulled almost all the other trusses over with it.
Don't know If I really answered your question very well. I guess my point in this story is to say that sheathed gables have to be braced for wind from EITHER side. And definitely brace them to the ground, or back to the interior of the building. (After they're set)Q: What do you call a couple that uses the rhythm method of birth control?A: Parents.