Beam stress calculation 1

[RobertHasty]

Hello,

I need a help with my weld stress calculation.
I have a rectangular tube supported by a rib. I have attached a hand-made drawing on the following link:

https://files.engineering.com/getfi...-4165-a80b-8727cfa904bf&file=Weld_problem.pdf

I have a fillet weld around a rib and on the bottom of the tube, but I am unsure about the other welds (top, left and right side of the tube). I have assumed that these welds are butt weld type.
And if they are a butt fillet type, may I assume that their height (or thickness) is the same as the pipe thickness (t on the drawing)?

Thanks a lot in advance.

Best,
Robert

 

[dhengr]

RobertHasty:
First, please put some dimensions, thicknesses, sizes, loads, materials specs., etc. on your sketch, so we know a bit more about what you are actually talking about. If ‘t’ is 1/16th inch thick and your sq. tube is 8" on a side, you have quite a different problem than if it’s a 8x8x.5" tube. Are the tube corners sq. or radiused? And again, it is a different problem is F = 100lbs. than if it equals a ton. Finally, a 1' long cantilever acts and is analyzed quite differently than a 20' long canti. And, these types of things are probably more important to a good solution to your problem than that ugly weld group is. You guys always seem to leave out the important engineering design info., and the penalty for that is that you don’t get very helpful answers. I think I know what you are trying to do, but with a complex joint like that, you can’t treat a whole bunch of different types and sizes of welds as lines, and then find some imaginary section properties for the group.

The stiffeners (ribs?), knee braces, whatever; one btwn. the canti. beam and the column, and 4 at the base are poorly placed. If they take any load, they are going to tend to punch right through the wall of the tube, or cause considerable deformation. The blackened welds you show (end views) of welds to the edges of these stiffeners are a bad detail, a weld that’s almost impossible to make with any degree of quality. Redo your sketch with the canti. beam, the column, a base pl. on the col., and no stiffeners, and the other above design info., and then lets take another shot at this.

 

[tmschrader]

Hello

In any case the effective weld size can not be greater then the tube thickness. As that will be the min thickness of weld joint. So your on the right track there.

 

[dik]

Why all the gusset plates?

Dik

 

[dik]

See CIDECT Design Guide 3, Section 3.9. Testing has established that fillet welds up to 10% greater than the tube thickness can give strengths approaching a CJP weld. Not necessary to use, but, handy to know. I usually design connections for approx 70% of the tube capacity to avoid CJP welds which are extremely expensive to do.

Dik