SkyCiv Moment Connection Calculator

A joint that transfers bending moment between a column and a beam, or between any two members. If the beam carries internal moment, the connection has to be able to transmit the load that moment produces.

The objective is to get as close as possible to a fixed joint, the fixity code FFFFFF, meaning rigid in all translational and rotational directions. That is where the alternative name comes from: rigid connections.

Shear connections depend mostly on the web of a section. A rigid joint adds to that by strengthening the connectivity of the flanges, using plate stiffeners, welds or other fixtures that increase rigidity between the members.

The result is a joint that can carry far more moment. The cost is material, and it is not a small difference: the same members cost significantly more to join this way than with a shear connection.

That economics is worth stating plainly, because it drives real design decisions. A typical structure has only one or two unique moment connections, precisely to keep that cost contained. They are used where the frame needs them, not by default.

Three arrangements cover most of what gets built, and the calculator handles all three.

Plates join the beam to the column, bolted or welded or both, to form a rigid fixture. In the arrangement below, two plates are bolted to the flanges of the beam to connect it to the column. As the beam bends, that action passes into the connected member.

A rigid plate welded to the end of the beam, running past one or both flanges. That extension is doing something specific: it creates leverage, so extra rows of high-strength bolts can sit outside the beam profile.

The larger moment arm is what raises stiffness and capacity, by resisting the tension and compression forces more efficiently. It suits high-stress seismic work and heavy structural frames.

A rigid plate welded to the beam end and bolted to the face of the column, but stopping at the flanges rather than running past them.

Tension and compression go into the column mainly through the high-strength bolts packed between the beam’s flanges. Less capacity than an extended plate, and in exchange a compact profile that lines up with the beam’s outer edges.

• Choose the connection type: flange plate, extended end plate or flush end plate.
• Set the members: the beam and column sections being joined.
• Define the plate and bolt details: plate sizes, and the bolt grade and arrangement.
• Enter the design actions: the bending moment and the shear at the joint.
• Pick the design method: ASD or LRFD, to AISC 360-16.

Calculate, and the capacities come back with utility ratios so you can see which component is closest to its limit.

Because these joints are expensive, the useful question is rarely whether one arrangement works. It is which of the three is the cheapest that still works, and that means checking all of them.

Running the checks to AISC 360-16 in ASD or LRFD without setting up the calculation by hand makes that comparison practical rather than theoretical, and the result comes with the working attached.

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