Moment of Inertia of weld on eccentric load 1

[Iasonasx]

In case we have a plate welded taking eccentric load, I was looking at books such as McCormac that use the formula for moment of inertia b*h^3/12+A*d^2. This may be a bit of a nuance or maybe too much into detail but it may still suggest a slightly different welding thickness (+/- 1/16th with rounding). So if we have a weld that goes around the plate that will receive the eccentric load, like a C shape,(Please see diagram) do we only consider the (b*h^3)/12 for the vertical section (I-2)and only the A*d^2 for the horizontals (I-1) or should we consider that the horizontals take [(b*h^3)/12]+[A*d^2]. I specifically refer to I-1 in the dagram. The I-2 is obvious. Thank you

 

[structSU10]

You are talking about using the elastic method, which is more conservative type of analysis. you can do P*e*c/I as shown in AISC 13th pg 8-12.

Another method is the instantaneous center of rotation method, also discussed in section 8 of AISC 13th. There are tables (table 8-8 would be what you are looking for) that give a coefficient to use to calculate capacity based on the weld geometry & load position.