Custom Steel Section
Custom Steel Section
(OP)
I am working on a project where the owner wants to make a custom (home made) steel rectangular HSS. I have currently designed these members as HSS, ASTM A-500 GR. B. The cost of rolling the HSS on a radius is blowing the budget so we are trying to investigate options. The members are full arches - inverted "U" and are to be one piece. We want to consider welding cut plates (strips) to form an arch... (2) plates would have the arch (radius) cut and the other (2) would be curved along the ID and OD and fully welded along the 4 edges. My concern is the possibility of residual stresses induced during the welding and subsequent cooling of the section. Wouldn't you have to anneal the section to relieve it of the welding stresses? Has anyone ever done this sort of thing? Thank you.






RE: Custom Steel Section
RE: Custom Steel Section
RE: Custom Steel Section
To put your mind at ease add a note on the fab dwgs..."sequence welding to avoid distortion"....a qulalified fab shop should do this anyway as standard pracice.
RE: Custom Steel Section
http://www.FerrellEngineering.com
RE: Custom Steel Section
The welds would be along the edges of square cut plates... please refer to attached sketch. Do you consider this a full pen weld? Should we lap the plate in the corner and weld on the outside only?
We are in the NW and from my research, I could only find one outfit that can do this size of rolling (near Portland, OR), but we do have fab shops that can make the welds... it's going to boil down to cost.
RE: Custom Steel Section
http://www.FerrellEngineering.com
RE: Custom Steel Section
RE: Custom Steel Section
RE: Custom Steel Section
Otion 2 would require a prepared edge and with the thickeness of pl of a 1/4" a partial pen would leave you with very little weld.
Anyway, since you mentioned that it will also have torsion, I would be hesitant to use either one..they would be ok for bending and shear. Torsion, causing rotation of the member x-section could tend to open up the root of these welds..not good.
Because of the torsion I would use option 2 but with a square grove(butt) weld with a backing bar. This would also faciliate fit-up. This is a FP weld only because of the presence of the torsion.
If you want it to look pretty, grind flush after welding.
RE: Custom Steel Section
My first choice for a cross section would be the following, assuming this was acceptable aesthetically. It is totally honest from the fab. and design standpoint and is most economical, so I'd fight for it. I would use 6" (+/-) wide flange plates and press or pull them to the webs for fit-up and welding. I would set the webs at 5" (+/-) wide, out-to-out, leaving .5" (+/-) of flange outstanding to receive a nice clean fillet weld. This has the potential of good, but simple, fit-up and welding, and as good a root condition as you are going to get short of a fillet on both sides of the web, and you have access problems on that account. I would cut the webs out of plate, in two or three pieces, 90° or 60° of arc. This gives you some economy btwn. plate size/waste and splice welding and clean-up. In cleaning up the cut web pieces, you could grind or nibble a 1/16th or 1/8th inch bevel on the webs, to pick up some weld throat, but this is expensive and not needing in the above cross section. This would be needed in your option #2, and possibly in SAIL's backer bar scheme. As SAIL mentioned, your option #1 is an almost impossible fit-up problem out in the fab. shop. But, easy to draw.
Omer Blodgett has several real good books on weld design and the design of fabed. structures.