All the examples that try and explain shear horizontal talk about lying a number of planks on top of each other and then subjecting them to a load and watching how they slide past each other.

I need a member/s to resist 17700lbs in a point load. If the member is a 16"(depth) by 8" then it seems to be fine from my new found understanding of shear but what about 2 8"x8" on top of each other?