why are gusset plates for braced frames so expensive?

[hippo11]

I always hear that you want to minimize the size of your gusset plate on a braced frame connection because the gusset plate is so expensive...My question is why? It's just a chunk of plate that has to be cut to size....if it's 2'x2' instead of 18"x18" what's the big deal? I always thought it was the welding that's expensive (labor time)...

 

[csd72]

hippo11,

I think its the wasted material that is the issue. Plate comes in rectangular sections and the odd shape means that much more plate gets wasted. Also the whole perimeter needs to be cut.

csd

 

[hippo11]

thanks...so say I have a wacky shaped gusset plate that's roughly 9 sq ft and 1" thick...that's a 375 pound plate, roughly 188 dollars. And to make it, they have to cut it from a stock piece of 1" plate, tracing the whole perimeter of the gusset plate shape, right?

So then, say some geometry changes, my top of footing gets lower for plumbing coordination, etc., and I still need the wacky shape but now it's 15 sq ft x 1" thick...that's a 625 pound plate, roughly 313 bucks...so my cost has gone up 125 bucks...what's the big deal? Everyone is always trying to minimize gusset plate size, I just don't see why...anyone know of any references I could read? maybe I'm missing something.

 

[CTSeng]

so what are standard plate dimensions that are order from a mill?

 

[csd72]

CTSeng,

It varies depending on the type of steel and the mill it is coming from. I would suggest you call the mill that supplies the steel to the local area.

hippo11,

I agree with you that there often seems to be a major issue made about minor cost variances. Unless there is a hundred of these things?

csd

 

[JStephen]

You are calculating the cost increase as just the price of the raw materials from the mill or warehouse. By the same reasoning, the price of a new car ought to be about $1,500. The cost of your engineering should be about a penny a page, for that matter.

For an odd shape, you're going to have some additional waste. To cut from 96" or 72" wide plates, you're going to have some waste. If the plate thickness or grade is one you don't normally use, then you'll likely buy a much bigger plate than you need. You're going to have shop labor to cut it, freight to haul it, cost of shop priming, cost of redrawing the thing to cut, cost of installation, and then overhead on top of everything. If the original piece is already built, you have the entire new cost, not just the cost difference. If there's just one or two pieces, then they have to be taken to the jobsite as separate loads, instead of as a truckload (and the same thing can happen bringing in raw material). If you just have one or two pieces, the cost of shop priming will be much higher- you can't just open a half-pint of primer and go at it. If the change is made as a field change, it may delay other work as well.