- #1
peleus
- 18
- 0
Hi all,
I'm trying to learn to do some basic calculations for welding, and I've been given the task in regards to finding out the weld sizes required for the loads being applied.
I've got a 1.2m wide staircase, with 6 stairs, attaching to two angular beams on the outside. They will be welded around the entire outside, with the dimensions of each step being 285mm x 10mm. I'm modelling a 2.2kN/m load across each step.
I've been trying to use Blodgett's method, treating the weld as a line in the hope of getting a weld size. The problem I'm having is I believe that Blodgett's method and outlines provided in many textbooks are based off a cantilevered load, where as I've got a pinned end on both sides, creating a statically intedeterminate beam.
My attempts so far have been including forces due to shear and bending, which I believe is incorrect considering my fixture's being considered. If I do a bending moment diagram & shear force diagram based off a fixed / roller support scenario then I'd get a shear force of 1.32kN, and a moment of 0 at each end.
Following that, the area of the line would be = 0.02 + 0.57 = 0.59
So force due to shear on each weld would be 1320 / 0.59 = 2237N.
Based of this, and an allowable stress of 140 MPa, it would result in throat thickness of 0.0159 mm, or a "0.023" weld. Clearly this looks way off.
If someone could run me through what I'm doing wrong, and the correct way to model this and calculate the weld, it would be greatly appreciated. Especially if I need to treat it as a fixed - fixed and finding out if forces such as a bending moment applies.
Also, I'll point out that in reality you most likely wouldn't do this type of calculation for this structure, and just do a solid weld all round - but as with everything it's the learning process of how to do it rather than simply the answer.
Thanks all for your help.
I'm trying to learn to do some basic calculations for welding, and I've been given the task in regards to finding out the weld sizes required for the loads being applied.
I've got a 1.2m wide staircase, with 6 stairs, attaching to two angular beams on the outside. They will be welded around the entire outside, with the dimensions of each step being 285mm x 10mm. I'm modelling a 2.2kN/m load across each step.
I've been trying to use Blodgett's method, treating the weld as a line in the hope of getting a weld size. The problem I'm having is I believe that Blodgett's method and outlines provided in many textbooks are based off a cantilevered load, where as I've got a pinned end on both sides, creating a statically intedeterminate beam.
My attempts so far have been including forces due to shear and bending, which I believe is incorrect considering my fixture's being considered. If I do a bending moment diagram & shear force diagram based off a fixed / roller support scenario then I'd get a shear force of 1.32kN, and a moment of 0 at each end.
Following that, the area of the line would be = 0.02 + 0.57 = 0.59
So force due to shear on each weld would be 1320 / 0.59 = 2237N.
Based of this, and an allowable stress of 140 MPa, it would result in throat thickness of 0.0159 mm, or a "0.023" weld. Clearly this looks way off.
If someone could run me through what I'm doing wrong, and the correct way to model this and calculate the weld, it would be greatly appreciated. Especially if I need to treat it as a fixed - fixed and finding out if forces such as a bending moment applies.
Also, I'll point out that in reality you most likely wouldn't do this type of calculation for this structure, and just do a solid weld all round - but as with everything it's the learning process of how to do it rather than simply the answer.
Thanks all for your help.