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Shear Flow for welds 1
- Thread starter struc100
- Start date
Hmmmm.....
Trickier than it seems at first glance, huh?
I do not think your "Q" calc is correct. The first moment of area of the side plate about the N.A. of the composite section = ZERO.
Which means your shear flow would be zero.
For design purposes, I would ignore the wideflange web completely and design the welds as if you were building a box shape member. That way you can use "Q" of the top/bottom flange. Y-bar would be to the centroid of "connected part" which would no be the flange.
I may be off base here....getting late.
Trickier than it seems at first glance, huh?
I do not think your "Q" calc is correct. The first moment of area of the side plate about the N.A. of the composite section = ZERO.
Which means your shear flow would be zero.
For design purposes, I would ignore the wideflange web completely and design the welds as if you were building a box shape member. That way you can use "Q" of the top/bottom flange. Y-bar would be to the centroid of "connected part" which would no be the flange.
I may be off base here....getting late.
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This is a trick question. There is no shear flow along that plane. This is not a composite section in the way you typically think of it. The neutral axis of all three parts are the same, therefore the welds only ensure that the pieces deflect together, nothing more.
To convince yourself, just look at Ipl + Ipl + IWF and you'll get the same answer as if you try to look at this as a composite section.
If you want to put numbers to this weld, I would determine how much of the load each plate takes (in plf), then size a skip weld to transfer that force (plf) into each plate.
To convince yourself, just look at Ipl + Ipl + IWF and you'll get the same answer as if you try to look at this as a composite section.
If you want to put numbers to this weld, I would determine how much of the load each plate takes (in plf), then size a skip weld to transfer that force (plf) into each plate.
Yes, I had a similar question about 4 years ago when I first started working.
I think your approach is reasonable. It will probably result in very low shear stresses since the plane is so far from the neutral axis.
I think I would probably still check it for how much force needs to be transferred into the plates. I only say that because that's the force transfer mechanism that I see.
I think your approach is reasonable. It will probably result in very low shear stresses since the plane is so far from the neutral axis.
I think I would probably still check it for how much force needs to be transferred into the plates. I only say that because that's the force transfer mechanism that I see.
I might check it both ways and use the higher of the two. The shear flow check might be very low because the shear plane under consideration is so far from the neutral axis.
I got my PE results in January. No new names for me. I just wanted to get rid of the EIT, but StructralPE was already taken.
I got my PE results in January. No new names for me. I just wanted to get rid of the EIT, but StructralPE was already taken.
I did just do a quick comparison for a 40' beam with 2 klf of loading. Your method gives higher stresses in the weld under these conditions, and it's by a large enough margin that I believe it would be true for most conditions.
I think I'll use your approach in the future, and would only check my suggestion above if I have a short, highly loaded beam.
I think I'll use your approach in the future, and would only check my suggestion above if I have a short, highly loaded beam.
He chose Lion because Toad was already taken.
The two added plates are not a very efficient way of reinforcing the beam in bending. Shear flow is the correct approach in determining the weld requirement, but struc100 has the wrong expression for Q.
Assuming the side plates terminate at the middle of the top and bottom flanges, Q is (bt[sub]f[/sub]/2)*(h/2-t[sub]f[/sub]/4). The shear in both top (or bottom) welds at any point along the beam is VQ/I where I is the moment of inertia of the combined section.
BA
The two added plates are not a very efficient way of reinforcing the beam in bending. Shear flow is the correct approach in determining the weld requirement, but struc100 has the wrong expression for Q.
Assuming the side plates terminate at the middle of the top and bottom flanges, Q is (bt[sub]f[/sub]/2)*(h/2-t[sub]f[/sub]/4). The shear in both top (or bottom) welds at any point along the beam is VQ/I where I is the moment of inertia of the combined section.
BA
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