SkyCiv Double Angle Connection Calculator

This is the most common shear connection in building steel, and its job is narrow: carry gravity load out of a beam and into the girder or column supporting it.

The calculator checks capacity against the AISC 360 limit states that apply, bolt shear, bearing, tearout, block shear and weld strength, in LRFD or ASD. Bolted and welded arrangements are both supported.

Two steel L-shapes placed back to back on either side of a beam’s web, transferring the end reaction, mostly vertical shear, into a column flange, column web or primary girder.

The angles sandwich the web, so the fasteners running through it cross two shear planes rather than one. That roughly doubles their capacity against an otherwise identical single angle detail, which is the whole reason the arrangement exists.

It behaves as a simple support. The beam is free to rotate at its ends without pushing significant bending moment into the members holding it up.

What the joint consists of depends on whether it is bolted or welded:

• Angle legs: two steel angle sections, equal or unequal leg, sandwiching the beam web.
• Web fasteners: bolts or welds joining the outstanding legs of both angles through the supported beam web.
• Support fasteners: bolts or welds securing the remaining legs to the supporting column or girder.
• Supported beam web: takes the shear transfer, and is checked for local rupture and bearing.
• Support member flange or web: the landing face the connection attaches to.

Fabrication stays simple because nothing is coped or fitted tightly. The parts only have to line up well enough for the fasteners to go through.

They turn up wherever shear demand is high enough to want double-shear fasteners:

• Secondary floor beams framing into primary girders.
• Beam-to-column shear connections in multi-storey frames, to either the web or the flange.
• Heavy industrial plant and equipment support platforms.
• Pedestrian bridges, roof trusses and framed structural openings.

The four arrangements differ only in what gets done in the shop and what gets done in the field:

• Bolted-bolted: bolted to the beam web and to the supporting member. The easiest to erect.
• Welded-bolted: shop-welded to the beam web, field-bolted to the column or girder.
• Bolted-welded: shop-bolted to the beam web, field-welded to the supporting structure.
• Welded-welded: every leg welded, usually on heavy-duty or shop-fabricated frames.

Choosing between them is a trade between fabrication cost and how fast the steel goes up. Shop welding is cheaper per weld than field welding, but field bolting beats both for erection speed.

• Select the section sizes: the supported beam and the supporting member, from the standard AISC databases.
• Define the angle geometry: profile dimensions, thickness, length and leg orientation.
• Configure the fasteners: bolt grade, diameter, spacing and edge distances, or weld size and length, for each side of the joint.
• Enter the design forces: the factored vertical shear, plus axial load where it applies, under LRFD or ASD.

Calculate, and the utility ratios and failure mode checks come back together, so you can see which limit state is closest before committing to an angle size or bolt layout.

The AISC 360 limit state equations for this detail are not difficult, but there are enough of them that working the set by hand for every beam on a floor plate is where the time goes, and where transcription errors creep in.

Automating them makes the layout worth optimising rather than just verifying. Change the angle thickness or the bolt spacing, see which check moves, and keep the governing ratio in view while you do it. The step-by-step reporting is what goes into the drawings.

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