Direct Answer
An end plate moment connection (EEP or 4E/8E end plate) is a bolted moment connection where a thick steel plate is shop-welded to the beam end and field-bolted to the column flange. The plate transfers moment through tensile bolt forces in the extended plate above and below the flanges. It is popular because it requires no field welding — only field bolting — which significantly speeds erection.
Full Explanation
End plate moment connections come in several configurations: 4-bolt unstiffened (4E), 8-bolt stiffened (8ES), and 8-bolt extended unstiffened (8E). AISC 358 Chapter 6 covers prequalified end plate connections for seismic moment frames. The shop work is demanding: the plate must be welded to the beam flanges and web with CJP or fillet welds per the design, and bolt holes must be precisely laid out to match the column flange bolt pattern. Tight tolerances on hole location (±1/32" typical) are required for field fit-up.
What This Means for Your Shop
End plate connections require precise hole layout and flat, plumb plate attachment. Warped end plates (from weld distortion) will not bear flush against the column flange, creating prying action that can overload the bolts. Control weld sequence and heat input to minimize distortion.
Common Mistakes
Welding the end plate in a single pass with high heat input, causing significant distortion. The plate must be flat and square to the beam axis within tight tolerances.
Recommended Process
Weld end plates with alternating, balanced weld sequences to control distortion. After welding, check plate flatness with a straightedge. If distortion exceeds tolerance, the plate must be pressed or heat-straightened before drilling.