reduction of bolt allowable in lap joint with packer in shea

huangyhg

reduction of bolt allowable in lap joint with packer in shea
in a structural steel or aluminium lap joint subject to shear load, with a shim (packer) in the joint, what is the reduction in the bolt allowable load when the packer is thick (more then 15% of bolt diameter). what is the method to calculate the bolt stress when the packer (shim) is more then about 15% the bolt diameter?.  
structural aluminium lap joint?
i would suggest that you carry out 2 checks.
1) calculate bending stresses in the bolt based on the bolt being bent into an s-shape (assume head and nut fixed in rotation and reaction forces at mid-thickness of plates) and then check for combined (bending) tension plus shear in the bolt using the normal formulae.
2) check stresses if the entire bolt rotates (as seen from the edge of the plate) without bending.  this will cause additional bearing stresses on the edges of the holes and additional tension on the bolt.
the bolts/rivets can be either steel or aluminium, the plates are aluminium