A truss chord accidentally bent in plane and in place.
A truss chord accidentally bent in plane and in place.
(OP)
Friends
The fabricator, by mistake has fabricated a truss diagonal a couple of inches short. The erector, erects the chords(pipe sections) first, then bolts the diagonals to the chord. To fit in the short diagonal, he forces his way. The result is a chord with a kink. And the kink is about 4 inches(10cm) from design axis.
The concern is the force has locally yielded the pipe section.
How would you evaluate the future performance of this pipe chord?
thanks in advance
ijr
The fabricator, by mistake has fabricated a truss diagonal a couple of inches short. The erector, erects the chords(pipe sections) first, then bolts the diagonals to the chord. To fit in the short diagonal, he forces his way. The result is a chord with a kink. And the kink is about 4 inches(10cm) from design axis.
The concern is the force has locally yielded the pipe section.
How would you evaluate the future performance of this pipe chord?
thanks in advance
ijr






RE: A truss chord accidentally bent in plane and in place.
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/
RE: A truss chord accidentally bent in plane and in place.
RE: A truss chord accidentally bent in plane and in place.
TehMightyEngineer: it is a tension chord. Why?
bootlegend : That is the plan that is resisted because of difficulty in removing the diagonal.
ijr
RE: A truss chord accidentally bent in plane and in place.
You got a chance then, I'd not even bother if it was the compression chord as post-buckling design is very involved if you've never done one.
I'd start by modeling it in your software of choice with accurate dimensions of the kink. See what flexural/torsional forces this results in and make sure it's not completely failing at first glance.
Where along the truss span is it kinked? Got any pictures of it you can share?
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/
RE: A truss chord accidentally bent in plane and in place.
I would consult the owner. If he is ok with a fix, have them cut it out and full pen welds.
If not, have them fabricate it right.
RE: A truss chord accidentally bent in plane and in place.
From a practical perspective, you shouldn't have to get to that point because a new web member should already be fabricated and on the way to the site. Sometimes owners are willing to accept the mistakes of a contractor...as long as an engineer accepts the liability.
RE: A truss chord accidentally bent in plane and in place.
Interested in seeing a photo or at least a sketch.
RE: A truss chord accidentally bent in plane and in place.
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/
RE: A truss chord accidentally bent in plane and in place.
You MUST determine where that force came from (a crane, sledge hammers, bolted stress at the connectins from some other parts still in the structure? ) If a crane, at least the forces are not locked in - other than at the other end of the truss.
If caused by bolting up the truss, then every other connection in the assembly is carrying the extra stress - waiting to fail under some future load.
RE: A truss chord accidentally bent in plane and in place.
Thanks for the great contribution and time. I mentioned the chord is a pipe section. It can easily bend anyway.
@TehMightyEngineer : The kink is at the node where the diagonal(brace) joins the chord. I am not allowed to share photos yet by the erector.
thanks
ijr
RE: A truss chord accidentally bent in plane and in place.
Dik
RE: A truss chord accidentally bent in plane and in place.
My company is hired by the erector to investigate. He is the boss and he is following the owner's orders. We want the chord replaced. But life is not that easy sometimes. We have to go on investigating all aspects of the problem and I want to see how my fellow engineers would review this problem.
ijr
RE: A truss chord accidentally bent in plane and in place.
Dik
RE: A truss chord accidentally bent in plane and in place.