All,

I am trying to model a bolted connection with a standoff between the two bolted components. In one test, I used the bolt series option to place a rigid element between the beam element and the standoff. This holds the stand off in place. In a second test, I bonded the standoff to the top component. The bolt force results differ drastically between these two tests. I see increased axial force and reduced bending moment when using the bolt series option.

I think the increased axial force is result of the rigidization of the standoff. I also think the decrease in bending moment is because more load is being transferred through the standoff. This bugs me since I am calculating a bolt margin that combines the axial, shear and bending moment. I cannot get a worst possible case when the axial force and bending moment are increasing and decreasing, respectively. 

I am leaning toward not using the bolt series option as I believe bonding the washer to the component produces more accurate bolt forces. Does anyone have any experience using the bolt series or a suggestion for moving forward? I attached my test model with results if you are interested. Thanks a lot!