Galvanizing Crack
Galvanizing Crack
(OP)
We have designed a roof truss and it was galvanized. During the galvanizing,the top of the post member cracked. The truss is made up of a bottom chord beam of W12x26, the sloped top chords are W10x22, and a center post of W6x15. The crack has occured at the top of the post where the two top chords attach. Our thinking is when heated the truss members had some warping. Then when cooled after dipping the truss was restrained such that the only free point was at the top of the post and thus it cracked under the residual loads. The post is appoximately 31% stressed with a maximum load of 4.5kip. The overall span of the truss is 36'-0" nominal.
We are thinking of having them drill a hole at the end of the crack to stop future propigating and then weld the crack. This will damage the galvanzing, but we are not to concerned about that.
Any thoughs on our proposed corrective action or any better suggestions would be greatly appreciated.
I have attempted to upload a picture of the crack and a sketch of the truss.
We are thinking of having them drill a hole at the end of the crack to stop future propigating and then weld the crack. This will damage the galvanzing, but we are not to concerned about that.
Any thoughs on our proposed corrective action or any better suggestions would be greatly appreciated.
I have attempted to upload a picture of the crack and a sketch of the truss.






RE: Galvanizing Crack
RE: Galvanizing Crack
Then, I'd install a cap plate on the assembly over top the W6 to help with any uplift loads on the truss and to help with the stresses in the repaired area. you can repair the galvanizing with a cold galv paint.
Easy to say now, but having a cap on the W6 originally may have kept it from cracking...
just thoughts....
RE: Galvanizing Crack
RE: Galvanizing Crack
You must fix that crack, the web of that W6 will be in compression.
I'd also install the cap or other stiffeners.
RE: Galvanizing Crack
I would remove the galvanizing around the tail of the crack with acid rather than grinding. That will help you find the actual end of the crack.
RE: Galvanizing Crack
RE: Galvanizing Crack
As an aside, the fabrication is quite clumsy. Rough end cuts, holes in the welds...