Local Flange Bending due to Weld Along Flange
Local Flange Bending due to Weld Along Flange
(OP)
I've got a piece of equipment that I need to suspend from a spring hanger that pins to lugs on an existing W12x53. The beams that frame in one end of this W12 conflict with the equipment during installation, so I am proposing to remove them and install a temporary beam directly above and parallel with this W12. The W12 top flange of the W12 would then be welded to the bottom flange of the temp beam.
I am somewhat familiar with prying calculations and familiar with local flange yielding due to point loads on a flange (as from a beam trolley). However, I do not know how to deal with local flange yielding in this situation.
Any thoughts on the matter folks?
Particulars are:
-W12x53 @ 39" long, A992, spring hanger lug at the midspan
-About 45 kip load
-The way the flanges are coped to frame into other steel, I can get 17" of weld along each side. The weld group is plenty good for the load. (Flange on the W12 is 0.575" so a sizable fillet is possible, though not necessary).
THANKS!!!
I am somewhat familiar with prying calculations and familiar with local flange yielding due to point loads on a flange (as from a beam trolley). However, I do not know how to deal with local flange yielding in this situation.
Any thoughts on the matter folks?
Particulars are:
-W12x53 @ 39" long, A992, spring hanger lug at the midspan
-About 45 kip load
-The way the flanges are coped to frame into other steel, I can get 17" of weld along each side. The weld group is plenty good for the load. (Flange on the W12 is 0.575" so a sizable fillet is possible, though not necessary).
THANKS!!!






RE: Local Flange Bending due to Weld Along Flange
BA
RE: Local Flange Bending due to Weld Along Flange
RE: Local Flange Bending due to Weld Along Flange
RE: Local Flange Bending due to Weld Along Flange
I think the applicable limits states for the temp beam are:
AISC J10.1 Flange Local Bending (make sure flange is thick enough)
AISC J10.2 Web Local Yielding (probably doesn't control)
and of course the typical beam bending, shear, and deflection checks for the temp beam.
RE: Local Flange Bending due to Weld Along Flange
You might be able to use part 15 of AISC about hangers - with the weld at the outside edge of the flange no prying action can occur, just normal bending of the flange. So table 15-1 may be applicable and conservative.
You might also consider just using a single hanger connection at the coped end of the existing beam rather than welding full length of the temporary beam - this might make disassembly simpler.
RE: Local Flange Bending due to Weld Along Flange
I see the issue as a local web yielding rather that a prying action. I deal with it quite a bit with point loads being placed on the bottom flanges by the wheels of a beam trolley, and struct210, I was not aware that AISC so narrowly defined local flange yielding; thanks for pointing that out. The typical shape of flange deformation one would see in a bolted hanger still seems like the mode in which my upper temporary beam's lower flanges will deform. That said, I'd like to follow ASME NUM-1-2009 in which they outline a method for analyzing local stresses in beam flanges with concentrated loads. However, ASME does not define a length or effective length of the affected flange, though I assume they had something in mind that was sufficient to assume that the flange was fixed at the web. If that's reasonable, I believe that the effective flange length as outlined in AISC is reasonable, but I have a distributed load along the length of weld. You folks think an additional 10tf beyond the end of weld would be the effective length? Seems like the section modulus of the flange may end up a bit high, though I guess if you really are distributing the load along the web, you are gaining a lot of flange area.
RE: Local Flange Bending due to Weld Along Flange
The temporary beam must be capable of carrying the full load laterally unbraced, unless you propose to add bracing.
If there is sufficient clearance to use a pair of trapeze hangers about 14" apart, that would seem to be a better solution than welding. Each trapeze could consist of a pair of all-thread rods fitted tight against the flange of the existing beam with a strap plate under the existing beam and another over the temporary beam.
BA
RE: Local Flange Bending due to Weld Along Flange
RE: Local Flange Bending due to Weld Along Flange
I would not use the bolted connection prying tables. The bending eccentricities are less in a bolted connection than what you'll have. I would think Table 15-1 is quite unconservative. Salman and Johnson has a good discussion on this (page 795 of the 4th edition).
RE: Local Flange Bending due to Weld Along Flange
And if I can ask a possibly stupid question, what is this Table 15-1? The 9th chapters aren't numbered that high and Table 15-1 in the 14th is about Crane Rail Splices. I do not have access to a 13th at this time.
Also, agree with BAretired - I'm assuming no contribution from whatever bracing effect may be seen by the temp beam and using L=Lu.
Unfortunately, the hanger clip and trapeze ideas, while valid, don't fit into the particulars of the situation. These, of course, are too numerous to show up on a simple sketch so none of you folks could have known about them. This all came about b/c of a ~80 kip piece of equipment was designed with lifting lugs that interfere by 5" with the steel required to support the thing. It's on us to fix it and hang the thing. Good times!
RE: Local Flange Bending due to Weld Along Flange
RE: Local Flange Bending due to Weld Along Flange
RE: Local Flange Bending due to Weld Along Flange
RE: Local Flange Bending due to Weld Along Flange
RE: Local Flange Bending due to Weld Along Flange
If I seen any of you folks out sometime, I'll buy you a beer.
RE: Local Flange Bending due to Weld Along Flange
BA
RE: Local Flange Bending due to Weld Along Flange
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RE: Local Flange Bending due to Weld Along Flange
RE: Local Flange Bending due to Weld Along Flange
I agree stress at the weld root is better to be avoided.
RE: Local Flange Bending due to Weld Along Flange
RE: Local Flange Bending due to Weld Along Flange
RE: Local Flange Bending due to Weld Along Flange