Gusset plate with large hole
Gusset plate with large hole
(OP)
So, here's an odd question. Working on a design-build turbine and generator replacement project. Client needed to move some cross-bracing up slightly for clearance. Modified the bracing and columns for the adjusted working points. There was a fire suppression valve that went through the new brace location but I was assured that the valve could be rotated to miss. Turns out that was wrong, the valve can't be touched.
So, we're past the point of no return and the new braces have to go in. The plan is to construct an over-sized gusset plate out of two halves with a 10" diameter hole when the halves are CJP welded together. This will allow the valve stem to penetrate the gusset. All my bolting connections, work points, welds, and such remain the same as my originally designed gusset, it just now got very fat in the middle to keep the cross section equivalent to the original gusset without the hole. Brace is tension only.
Other than tension failure of the gusset at the hole and making sure I have enough distance between the ends of the gusset and the hole (Whitmore section) I can't think of anything else to check. There's gotta be something I'm missing, it seems like having a 10" hole in a gusset plate should be a much bigger deal.
So, we're past the point of no return and the new braces have to go in. The plan is to construct an over-sized gusset plate out of two halves with a 10" diameter hole when the halves are CJP welded together. This will allow the valve stem to penetrate the gusset. All my bolting connections, work points, welds, and such remain the same as my originally designed gusset, it just now got very fat in the middle to keep the cross section equivalent to the original gusset without the hole. Brace is tension only.
Other than tension failure of the gusset at the hole and making sure I have enough distance between the ends of the gusset and the hole (Whitmore section) I can't think of anything else to check. There's gotta be something I'm missing, it seems like having a 10" hole in a gusset plate should be a much bigger deal.
Maine EIT, Civil/Structural.






RE: Gusset plate with large hole
RE: Gusset plate with large hole
I've attached a picture showing the original and a rough sketch of the new gusset plate geometry.
Maine EIT, Civil/Structural.
RE: Gusset plate with large hole
RE: Gusset plate with large hole
RE: Gusset plate with large hole
Column only. This is at the baseplate (see previous attached picture).
As best I can tell the uniform force method will apply for a case similar to special case 3 in the manual. The brace, column, and gusset to column weld should see the exact same forces as they did in my non-doughnut gusset plate.
A moment shouldn't develop at the connections as the centeroid of the weld and bolt group still pass through the working point axis of the brace. You did remind me that some small moment will develop in the middle of the gusset as the net cross-section is no longer aligned to the working axis of the brace but I imagine this will be negligible.
Yeah, I can quickly make this in a FEA program.
Maine EIT, Civil/Structural.
RE: Gusset plate with large hole
Just out of curiosity, what program do you use for FEA?
RE: Gusset plate with large hole
Looking to get my boss to switch over to RISA-3D. Probably our biggest sticking point is RISA appears to be even less of a FEA program (que JoshPlum from RISA telling me it's the best).
Maine EIT, Civil/Structural.
RE: Gusset plate with large hole
RE: Gusset plate with large hole
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Gusset plate with large hole
RE: Gusset plate with large hole
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Gusset plate with large hole
SAIL3: There is enough length for the typical 30 degree Whitmore section stress flow. I would imagine a 10" diameter hole in a 3 foot wide plate would be relatively small of a stress riser but you are correct. We did add a little fat because of this.
Maine EIT, Civil/Structural.
RE: Gusset plate with large hole
Maine EIT, Civil/Structural.
RE: Gusset plate with large hole
Maine EIT, Civil/Structural.
RE: Gusset plate with large hole
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Gusset plate with large hole
Maine EIT, Civil/Structural.
RE: Gusset plate with large hole
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Gusset plate with large hole
In this job speed is worth more than money by a large amount. For example when we told the client would be expensive to do the bracing modification it was almost like they handed us a blank check and said "do what you need to do, just make it happen."
For a little background, this turbine/generator will allow the client to run 100% off grid and they need it in by January 1st. All was well until the condenser they purchased became unavailable and everyone had to do last minute redesigns to make a new condenser work in addition to all the work still remaining on the turbine and generator.
Maine EIT, Civil/Structural.
RE: Gusset plate with large hole
RE: Gusset plate with large hole
Maine EIT, Civil/Structural.