Built-Up Section - T + HSS with stitch welding on edge
Built-Up Section - T + HSS with stitch welding on edge
(OP)
I'm in process of designing a frame - and I'm curious about the length and spacing of welding (stitch weld, on edges) that will be required. The material is actually 316L stainless steel, but apart from that, I'm using standard structural shapes. In short, it's an L shape resting on top of an HSS rectangular member.
The orientation is such:
L
|_|
Note that the HSS has a top, I just couldn't figure out how to draw it using text.
This will be subjected to a distributed load.
The size of the L is 3 x 3 x 1/4" T
The size of the HSS is 4 x 3 x 3/16" T
I'm not the strongest in mechanics, because it's been many years since school and furthermore, my professor was not very good to begin with. However, I seem to have calculated out the moment of inertia of the combined section, though Solidworks shows something slightly different.
I'm getting the following properties:
Solidworks actually reports the Ixx-total as being 14.5, but I never quite understood that program 100%. I know that it likes to re-orient the axes, which is probably accounting for the different in values (assuming mine are correct).
Now the next part is how to actually calculate the resultant stresses in the weld, as they try to slide past each other during bending.
Do I use the shear flow equation? Or do I want to look at the moment at that point above the neutral axis, which is at 4" from the bottom left corner, or basically 0.934 above the centroid.
Any help would be greatly appreciated.
The orientation is such:
L
|_|
Note that the HSS has a top, I just couldn't figure out how to draw it using text.
This will be subjected to a distributed load.
The size of the L is 3 x 3 x 1/4" T
The size of the HSS is 4 x 3 x 3/16" T
I'm not the strongest in mechanics, because it's been many years since school and furthermore, my professor was not very good to begin with. However, I seem to have calculated out the moment of inertia of the combined section, though Solidworks shows something slightly different.
I'm getting the following properties:
Atotal = 3.84 sq.in.
Centroid-System = C(1.253, 3.066) from the bottom left corner
Ixx-1 of L = I-initial + Ad^2 = 1.24 + (1.44 * 1.776^2) = 5.782 in^4
Ixx-2 of HSS = I-initial + Ad^2 = 5.24 + (2.4 * 1.066^2) = 7.967 in^4
Ixx-total = 5.782 + 7.967 = 13.749 in^4
Solidworks actually reports the Ixx-total as being 14.5, but I never quite understood that program 100%. I know that it likes to re-orient the axes, which is probably accounting for the different in values (assuming mine are correct).
Now the next part is how to actually calculate the resultant stresses in the weld, as they try to slide past each other during bending.
Do I use the shear flow equation? Or do I want to look at the moment at that point above the neutral axis, which is at 4" from the bottom left corner, or basically 0.934 above the centroid.
Any help would be greatly appreciated.






RE: Built-Up Section - T + HSS with stitch welding on edge
If the member is only significantly acting in bending, the required connection strength is simply from shear flow. However, depending on what else is going on, specifically with your connections, there may be additional stresses trying to cross the weld plane.
RE: Built-Up Section - T + HSS with stitch welding on edge
That's using q = VQ / I where:
V = 5000lbs / 2 = 2500 lbs
I = 13.749 in4
Q = y' * A'
y' is 4.842 (CG angle) - 3.066 (CG entire section) = 1.776 in
A' is 1.44 (area angle)
Does that sound about right?
If so, then the strength of the weld would need to be determined, which is just the cross section of the weld * the allowable stress. At that point, I could just get the equivalent required length of weld and then space out accordingly, correct?
RE: Built-Up Section - T + HSS with stitch welding on edge
Some background: https://www.aisc.org/WorkArea/showcontent.aspx?id=...
That said, 465 lbs/in. of demand is peanuts.
"It is imperative Cunth doesn't get his hands on those codes."
RE: Built-Up Section - T + HSS with stitch welding on edge