Block Shear Strength Calculation with Tensile and Shear forces applied together

[bvass]

Hey all,

I am checking an engineer's mathcad design template for a simple pinned support using clip angles. For a block shear check on the web of the connecting beam, he uses a resultant force from the shear and tensile forces to check his block shear capacity against. When the block shear resistances are developed the tensile and shear failure planes are converted into component resistances and the capacity is developed. Is this allowed? I'm having a hard to visualizing this. I see one failure plane (Area 1 and Area 2) due to the tensile force, and the other failure plane (Area 1 and Area 3) due solely to the applied shear force. Should each not be checked against their applied force individually?

The attached jpeg explains what I'm talking about. Thanks!



Brad

 

[Agent666]

Please draw a sketch of the cases they consider. A spreadsheet output means we have to decifer what they are specifically checking.

When considering block shear you do consider a combination of shear and tension depending on the failure plane being looked at.

 

[bvass]

They are considering the failure plane denoted by A1 (blue) and A2 (red) for the axial load and the failure plane A1 (blue) on only one side of the clip and A3 (green) for the shear load. Let me know if the sketch on the previously attached jpeg still isn't clear and I can draw one up.

Thanks,

Brad

 

[Agent666]

I would say that's correct in the sense that it's one possible failure plane, but you may find for axial load that having the green A3 in tension, and the bottom blue A1 in shear would be the most critical as you note, especially if the angle cleat is very close to the top of the cope as it's shown. I have not looked at the individual equations in detail, but in theory the two cases discribed are valid failure planes that would be assessed for block shear, they aren't looking at all possibilities though, but it is dependent on the actual geometry.