Designing a Welded Shear Tab for Horizontal Shear

[strcengr]

Hi All,

I have the un-ideal situation of designing a welded shear tab for some horizontal shear (about a kip or so).

What moment arm would you consider for designing the weak-axis flexure induced in the plate?

My thought is that it would be the "b" dimension I show in the image given that the plate is restrained on 3 sides to the beam web and not seeing much bending.

Additionally, what would you design shear tab to column flange weld for? 5/8 * thickness of the plate per AISC manual part 9?

I can't seem to find any examples of this in AISC literature so references are welcome..

 

[Lomarandil]

First pass, design the plate for weak axis bending with moment arm "a" -- centroid to centroid of weld groups.

Need to sharpen the pencil? Once you've solved the stresses in your weld group (plate to beam), account for those reactions in the weld toes (left of the centroid) as countering the applied load at moment arm "a".

Shear tab weld should be designed for the vector sum of stresses, but given the directionality and magnitude I doubt it changes your eventual weld size.

 

[strcengr]

Interesting - thanks Lomarandil.

Would you design the shear tab weld to consider the flexure due to weak axis bending?

i.e. the weld on one side of the tab would be in compression and the other side be in tension..

Have done this in the past but it seems a bit odd that weld resists moment.

 

[skeletron]

If you are checking the shear tab, I expect the eccentricity would be "b".
If you are checking the beam web resistance, I expect the eccentricity would be "a".

My reference is for beam-to-beam extended shear tab checks, where the shear tab is welded 3-sides to a supporting beam and bolted to the supported beam. Similar, but different, but I think a very similar yield line method could be applied. I take the minimum capacity of the shear tab flexural, beam web flexural using the yield lines with load toward the web, and then reverse the direction of the load.

I would ultimately design the shear tab to column flange weld for the vector sum of the stresses.
Judging by the W6 beam, a 1/4" fillet maxes out the capacity of the available web thicknesses.

My usual question with weak axis shear is: how is this applied to the beam? how is the force flowing into the web to get to the connection? You almost wish there was some horizontal bracing, end plate connection, or even a double clip angle. But seems like it's outside the scope of the question.

 

[dik]

Can you weld it along the 'b' side and use b/2 as your moment arm?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[strcengr]

@skeletron is there an AISC example with the beam to beam connection you mentioned that I can reference?

@dik why b/2 for the moment arm rather than b?

Appreciate the responses so far everyone

 

[dik]

Welded at each end, I'd consider it fixed...Stiffness of what it's attached to is much greater than the plate at each end... therefore, fixed...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[271828]

Use b and then consider it rotationally fixed at the column and at the beam. Thus, the moment would be V*b/2 similar to what dik is saying.

 

[jerseyshore]

I know your load is small, but you could also use a bent plate to give yourself a little bit of extra weld along the column.

 

[dik]

I'd design the weld connection for a fixed end... it's just the way I do things...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik