Bolt Prying Load

When a flange is pulled apart, the far edge can bear against its mate and lever the joint open — prying. The bolt then carries more than the applied load. With a rigid flange the amplification is simply (a+b)/b.

Rigid-flange worst case. A thin, flexible flange prys less — AISC gives a thickness rule that reduces Q. Move the bolt closer to the load (smaller a) to cut prying.