Reinforcing ring
Reinforcing ring
(OP)
I need an education concerning a reinforcing ring around a a waste water tank. The current design calls for a rolled angle with one toe welded to the outside of the tank wall and one leg vertically down. Common enough design. My question is, what does the vertical leg bring to the party? Wouldn't a flat bar rolled on edge that had an equal or higher section mod. do just as well? I'm not an engineer, just a steel guy trying to understand this.
Thanks
Thanks





RE: Reinforcing ring
If you have any further questions, please do ask.
RE: Reinforcing ring
The top of the shell must be stiffened in fragile, flat bottomed tanks to prevent excessive deflection at the roof/shell juncture due to snow or wind loadings.
RE: Reinforcing ring
If you use a flat bar you still have the tank wall's contribution to the equation. Then if you use a bar with a high section modulus, but a lighter weight than the angle, don't you achieve the same thing and also save material at the same time?
RE: Reinforcing ring
RE: Reinforcing ring
To understand why a T section is much better than a simple bar, look up how to calculate I, the second moment of area, which is essentially a measure of how stiff a particular section is. Formula exist for standard shapes which can easily demonstrate why particular shapes are better than others.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Reinforcing ring
RE: Reinforcing ring
In essence the simple answer to the op is that weight for weight an angle is simply much more efficient at providing stiffness than a flat bar due to the second moment of area calculation.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Reinforcing ring
We've rolled these angles successfully for a customer for about twenty years. Life was all good when everything was just A-36 material. Then along comes material with multiple certification, higher yields and higher tensiles. Now an angle that I may have rolled down to a 3' or 4' radius starts fracturing the heel at 30' and 40' radii.
We've had a discussion with a metalurgist and he confirmed that when the tensiles and yields go up, we lose the ductility. My customer is not wanting to stop using angle, but we can't predict the fracturing from one batch of material to the next. My customer also doesn't want to absorb the added cost to repair all of these fractures, and understands that we can't either. We're just trying to find a way out.
RE: Reinforcing ring
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Reinforcing ring
If your company only does rolling, this puts you in quite a bind. If you can competitively burn and break plate, perhaps that would be the more effecitve solution (think plan view octagon).
RE: Reinforcing ring
Try grinding a 1/16" - 1/8" radius on the heel of the angle before you roll form it. The fracture is starting at the sharp edge/corner or little nicks in that corner. Don’t use a real course grinding wheel either. Also, a little heat would help, maybe not even heating the whole section, but just the heel area. Play a rose bud torch or ribbon burner on that area to put a few hundred degrees of heat into the heel. Experiment a bit with these ideas. Also, the mill certs. on some angles and bar stock can be kinda loose unless you order it under tighter control. Otherwise, I agree with what’s been said above about an angle being pretty efficient for this detail. Also, a higher strength Fy & Fu to match the tank sheets may not be needed, rather something higher than A36, but not Fy = 50ksi or more.
RE: Reinforcing ring
Thanks for the suggestions, but my fracturing doesn't occur at the corner of the heel. The angle is 5" x 3 1/2" x 3/8" with the 5" leg rolled in. The fractures occur 3/8" down from the true heel of the angle, straight across from the inside face of the leg. Anytime your rolling angles with the leg in, that is where the most stress is placed.
As to heat; while it might help some, it's just not practical to try and heat 40' lengths.
Pertaining to the chemistry; we tend to do these in lots of 20 to 40 pieces per order. All of the warehouses around us only stock the multiple certified material that we're having the problems with. The straight A-36 only is just not available unless you want to buy the product of a heat at the mill, and that just can't happen. The mills aren't going to run plain A-36 anymore when they can cover a broad spectrum of certs. with the same effort.
RE: Reinforcing ring
Does it help to roll it 2 or 3 times, each to a smaller radius?
RE: Reinforcing ring
It is indeed a lack of ductility, due to the elevated yields and tensiles, but we just can't get the A36 material anymore.
Whenever we're rolling a large angle like this, it's always an incremental process that will require several passes.If you try to roll a bunch of angles like this in one pass, they'll be all over the place as far as radius goes.
RE: Reinforcing ring
RE: Reinforcing ring
I have not. We're not AISC members, so I'm not familiar with a Solutions Centre. How does that work?
RE: Reinforcing ring
I don't know either and am not in the US, but I found a reference to that resource in this paper which I found by googling.
http://www.modernsteel.com/Uploads/Issues/January_...