A moment connection is a beam-to-column joint designed to transfer bending as well as shear, so the angle between the beam and the column stays essentially fixed under load. A shear connection, by contrast, carries the beam reaction and lets the beam end rotate.
That single difference decides whether a frame needs bracing to stand up, and it is the reason moment connections cost what they do.
What “Moment” Means Here
Bending in a beam is resisted mostly by its flanges: one pulls, one pushes. To carry that bending across into a column, the connection has to pick up both of those forces. That is why moment connections attach the flanges, and shear connections usually only attach the web.
Those flange forces do not stop at the column face. They push and pull on the column flange, which is why moment connections usually need continuity plates inside the column lined up with the beam flanges, and often web doubler plates as well. That hidden work inside the column is a large part of the cost.
Shear vs Moment: What Changes
| Shear connection | Moment connection | |
|---|---|---|
| Transfers | Vertical reaction | Reaction plus bending |
| Beam end | Rotates | Held at essentially fixed angle |
| Typically attaches | Web | Both flanges and the web |
| Column work needed | Little or none | Continuity plates, sometimes doublers |
| Frame stability from | Bracing or shear walls | The frame itself |
| Relative cost | Low | High |
A shear connection is the default because it is cheap and fast. Moment connections appear where bracing cannot go: an open facade, a wide opening, a bay that has to stay clear.
Both types still rely on ordinary connection hardware and the same section properties. The plates and angles used are the same family covered in our gusset plate guide, the bolts come from the structural family in our bolt grades guide, and the member sizes come from the wide flange beam sizes chart.
The Main Types
Welded flange, bolted web
The beam flanges are welded directly to the column with complete joint penetration groove welds; the web is bolted to a shear tab. Common, compact, and dependent on weld quality at exactly the point of highest stress.
Bolted end plate
A plate is shop welded to the beam end and bolted to the column in the field. It moves the welding into the shop, where it is easier to control, and makes erection a bolting operation. The plate and the bolt layout both have to be designed for the flange forces.
Bolted flange plate
Plates are welded to the column and bolted to the top and bottom of the beam flanges. More pieces, but again most of the welding happens in the shop.
Reduced beam section
Part of the beam flange is deliberately cut away a short distance from the column, so that when the frame is pushed hard the beam yields there rather than at the weld. It looks like damage and is the opposite: a designed weak point that protects the connection. It is a seismic detail, not something to replicate casually.
Why Welding Quality Decides This Connection
Moment connections are the clearest case in structural steel of a detail being rewritten because of how it failed in a real event.
The welded detail used almost universally in the US between roughly 1970 and 1994 was prescribed for seismic use by the building code of the time. After the 1994 Northridge earthquake it was found not to work as assumed. In the words of FEMA-350, Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings, prepared by the SAC Joint Venture: “Following the Northridge earthquake, it was discovered that many of these beam-column connections had experienced brittle fractures at the joints between the beam flanges and column flanges.” The document states plainly that the old detail “is no longer considered to be an acceptable design for seismic applications” (checked September 2026).
What came out of that work changed practice: tougher weld metal, removal of weld backing at the bottom flange with back-gouging and a reinforcing fillet, prequalified connection details, and much tighter quality assurance. The welding itself is governed by the structural welding code; the American Welding Society notes it has authored more than 350 standards including D1.1, the Structural Welding Code for steel, which it describes as one of the most-referenced codes in the world (checked September 2026).
On drawings, all of that arrives as weld symbols, and reading them correctly is not optional on a moment connection. Our weld symbol guide covers what the numbers and flags mean.
What This Means on a Real Job
Three practical consequences follow from all of this.
Moment connections are specified, never substituted. Swapping a moment connection for a shear connection removes the frame’s ability to stand up on its own. Swapping the other way loads a column that was never detailed for it.
Inspection is part of the design. A complete joint penetration weld is only worth what the inspection behind it is worth, which is why these joints attract non-destructive testing requirements.
Column work drives the cost. Continuity plates and doublers are inside the column and invisible in the finished building, but they are often the most expensive part of the connection to fabricate.
Moment Connection FAQ
What is the difference between a moment connection and a fixed connection?
In everyday use they mean the same thing: a joint that transfers bending. “Fixed” is the idealization used in analysis; real connections are stiff rather than perfectly rigid, and the design accounts for that.
Do moment connections have to be welded?
No. Bolted end plate and bolted flange plate connections transfer moment without field welding, which is one reason they are popular. There is usually shop welding somewhere in the assembly.
Why are continuity plates needed?
The beam flange forces land on the column flange as concentrated push and pull. Continuity plates sit inside the column in line with the beam flanges and carry those forces through, so the column flange does not bend and the web does not buckle locally.
Why is a piece cut out of the beam flange near some connections?
That is a reduced beam section, sometimes called a dogbone. It moves yielding away from the welded joint and into the beam, where ductile behavior is wanted. It is deliberate and must not be repaired or reinforced without the engineer of record.
Can I add a moment connection to an existing frame?
Only as a designed modification. It changes how load moves through the whole frame and imposes forces on columns and foundations that may not have been designed for them. That is an engineer’s decision, with drawings.
The Short Version
Shear connections carry the reaction and let the beam end rotate; moment connections carry bending too, which is what lets a frame stand without bracing. Doing that means developing both flanges into the column, which usually means continuity plates and sometimes doublers. Northridge showed the consequences of getting the welded detail wrong, and modern practice is the answer to it. Which connection goes where is set by the engineer of record and shown on the drawings.
Reference information only, not engineering advice. Disclaimer.