Direct Answer
A framing angle (clip angle) connects the beam web to the support — transferring shear vertically. A seat angle provides a bearing surface at the beam bottom flange — the beam sits on it. These are distinct connection elements with different structural roles. Many connections use both: a bottom seat angle for vertical load and a top clip angle for stability.
Full Explanation
Framing (clip) angle details: attached to the support (column or girder web), then the outstanding leg bolted to the beam web. They resist shear through bearing on bolts and web shear. Seat angle details: the horizontal leg provides bearing for the beam bottom flange; the vertical leg is bolted or welded to the support. The seat carries the beam's end reaction by bearing. When used together, the seat carries vertical load while the top clip angle provides lateral stability and prevents the beam from rotating off the seat. AISC Manual Tables 10-5 (framing angles), 10-7 (unstiffened seats), and 10-8 (stiffened seats) provide design capacity.
What This Means for Your Shop
Seat angles must be precisely located in elevation — the beam bottom flange must land on the seat horizontal leg without shimming. A seat that is 1/4" too low forces the beam to carry partial bearing on the seat edge rather than full bearing on the flat, reducing capacity.
Common Mistakes
Installing a seat angle 1/4" below the required elevation because it 'looks close enough.' The required bearing length on the seat horizontal leg is a structural dimension — field adjustment by shimming is acceptable only with engineer approval.
Recommended Process
Verify seat angle elevation during final column inspection before shipping. Use an optical level or laser to confirm that all seats on a multi-connection column are at the correct elevation relative to each other and to the base plate.