Question about example from Blodgett

[Perception]

Hello everyone,

I am looking at an example from Blodgett where the resultant shear force on a weld group is found. The weld group is loaded with both an in plane and out of plane load at an eccentricity. The example is shown in the attachment.

What I don't understand about the example is why there is no direct shear force on the weld due to the 200 lb force. I think a direct shear of (200 lb)/(3 in + 4 in) should be put on the weld group. Am I missing something?

Thanks

 

[JAE]

I think you are correct....there is additional shear on the weld overall. The moment from the horizontal force (200 lbs.) isn't a pure moment acting on the group but a force causing a moment...just like the vertical 300 lb. force.

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[Perception]

JAE,

I agree with you. The only logic I could come up with is Blodgett is taking the direction of the vector into account. Although, when designing a weld I have never taken the direction of the vectors into account. I just make everything positive and find the resultant force.

 

[KootK]

It feels like blasphemy to say so but, I agree, it appears that the example is in error.

The only logic I could come up with is Blodgett is taking the direction of the vector into account.

In figure 26, I think that the 211 lb force is actually pointing the wrong way. Pointed the right way, I believe that it would indeed be additive to the direct horizontal shear.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.