Steel Connection Types: A Visual Guide for Estimators

Steel connections are where estimating gets complicated. Two projects with identical tonnage can have wildly different fabrication costs based solely on their connections. A warehouse with simple shear connections might cost $3,800/ton fabricated, while a seismic moment frame building of the same tonnage could run $6,500/ton. Understanding connection types is essential for accurate estimating.

This guide covers the most common structural steel connections, what they cost to fabricate, and what estimators need to know about each one.

Shear Connections (Simple Connections)

Shear connections transfer vertical load (shear) from beams to columns or girders without restraining rotation. They are the most common and economical connections in steel construction.

Single Plate (Shear Tab)

A single plate welded to the supporting member in the shop, with bolts connecting to the beam web in the field.

Components:

One plate (typically 1/4" or 3/8" thick)
2-5 bolts (3/4" A325 is standard)
Shop fillet weld on one side

Estimating notes:

Simplest and cheapest shear connection
Shop time: minimal — one plate, one weld, one set of holes
Field time: fastest to erect — ironworker slides beam onto bolts
Typical capacity: up to 100-150 kips depending on plate size and bolt count
Cost impact: baseline — this is your lowest-cost connection

Double Angle

Two angles, one on each side of the beam web, bolted or welded to the supporting member.

Components:

Two angles (typically L3-1/2x3-1/2x5/16 or L4x3-1/2x1/4)
3-6 bolts per angle to beam web
3-6 bolts or fillet welds to support

Estimating notes:

More material and labor than a shear tab
Common in older designs and some engineering firms' standard practice
Shop time: two angles to cut, punch, and fit vs. one plate
Higher capacity than single plate connections
Cost impact: 20-40% more than shear tab for same beam size

Seated Connection

An angle or tee welded to the column that the beam sits on, like a shelf. A top angle provides lateral stability.

Components:

Seat angle or WT (bottom)
Top angle (smaller, for stability)
Welds and/or bolts

Estimating notes:

Used when the beam cannot reach the column web (e.g., column flange connections)
More forgiving of erection tolerance — the beam sits on the seat
Requires stiffener on the seat angle for larger reactions
Cost impact: similar to double angles

Web Shear Plate (Beam-to-Beam)

When a beam frames into the web of a girder, a single plate is welded into a slot cut in the girder web (extended shear tab) or bolted to the girder web.

Components:

One plate, holes for beam web bolts
Weld or bolts to girder
Possible cope on the beam to clear the girder flanges

Estimating notes:

The cope is the expensive part. Coping adds $50-$150 per beam in shop labor depending on complexity
Single cope (top flange only) vs. double cope (top and bottom) — double cope costs roughly twice as much
Cost impact: cope adds 15-25% to the beam's fabrication cost

Moment Connections

Moment connections transfer both shear and bending moment, creating rigid frame action for lateral resistance. They are significantly more expensive than shear connections.

Bolted Flange Plate

Plates welded to the column in the shop, bolted to the beam flanges in the field.

Components:

Top and bottom flange plates (sized to transfer moment)
Shear connection (shear tab or angles) for vertical load
4-12+ bolts per flange plate
Continuity plates (stiffeners) inside the column at each flange level

Estimating notes:

Continuity plates are often the biggest cost driver — they require fitting inside the column between flanges, overhead welding, and UT inspection
Flange plates add material weight (heavier plates for higher moments)
Field bolt-up is labor-intensive with many bolts to tension
Cost impact: 2-3x a shear connection for the same beam-column pair

Welded Flange / Bolted Web

Beam flanges are welded directly to the column flange with CJP (Complete Joint Penetration) groove welds. Web connection is bolted with a shear tab.

Components:

CJP groove welds at both flanges
Shear tab for web connection
Continuity plates inside column
Weld access holes in beam web
Backing bars at CJP joints

Estimating notes:

This is the most common moment connection type in seismic design
CJP welds are expensive: they require weld procedure qualification, certified welders, and ultrasonic testing (UT) of every joint
UT inspection at $150-$300 per joint adds up fast — a 4-story building might have 100+ CJP joints
Backing bars and weld access holes add shop time
Cost impact: 3-4x a shear connection

Extended End Plate

A thick plate welded to the end of the beam, with bolts connecting the plate to the column flange.

Components:

Thick end plate (3/4" to 1-1/2") welded to beam
8-12+ high-strength bolts (often A490)
Possible stiffener plates on the beam and column
Continuity plates inside column

Estimating notes:

Keeps all welding in the shop (no field welding)
Thick plates and many bolts = heavy connection
End plate must be machined flat for proper bolt bearing
Popular in pre-engineered metal buildings and some commercial designs
Cost impact: 2-3x a shear connection

Brace Connections

Braces resist lateral forces through axial tension and compression. Their connections are often the most material-intensive in the building.

Gusset Plate Connection

A plate (gusset) connects the brace to the beam-column joint or to a beam or column directly.

Components:

Gusset plate (often 1/2" to 1" thick, can be quite large)
Bolts or welds connecting brace to gusset
Welds connecting gusset to beam and column
Often includes a shear tab for the beam connection integrated into the gusset

Estimating notes:

Gusset plate weight can be surprisingly high — a single large gusset may weigh 200-400 lbs
In seismic design (SCBF, OCBF), gusset plates must meet specific geometry requirements that often make them larger than strictly required for strength
Seismic gusset detailing adds engineering cost (delegated design by the fabricator's PE)
Cost impact: gusset connections can double the fabrication cost of the brace member itself

HSS Brace Splice

When a brace is too long for one piece or when field conditions require a splice.

Components:

Flare bevel groove welds or bolted plate splice
Splice plates (for bolted connections)

Estimating notes:

HSS splices are more complex than wide flange splices because of the closed section
Welded splices require special procedures for the curved HSS corners
Cost impact: add $300-$800 per splice depending on HSS size

Column Connections

Column Splice

Columns are typically spliced every 2-3 stories to manage shipping lengths.

Components:

Splice plates (flange and web) with bolts — typical for gravity columns
CJP groove welds — required for moment frame and seismic columns
Erection plates or angles for temporary alignment

Estimating notes:

Bolted splices are straightforward: 4 plates, bearing bolts, nominal shop time
CJP welded splices are expensive: full-penetration welds on both flanges, UT testing, backing bars
Column sizes often change at splices (W14x176 below, W14x90 above), requiring fill plates
Cost impact: bolted splice $500-$1,000; CJP splice $2,000-$4,000 per location

Base Plate Connection

Where the column meets the foundation.

Components:

Base plate (sized for bearing on concrete)
Anchor bolts (4 for gravity columns, 4-8+ for moment frame columns)
Grout (by others, but affects your anchor bolt projection)
Shear lug (if required for lateral load transfer)

Estimating notes:

Base plate thickness ranges from 3/4" for light columns to 2-3" for heavy moment frame columns
Heavy base plates are expensive material — a 2" x 24" x 24" plate weighs about 327 lbs
Anchor bolt embedment and projection must be coordinated with the concrete contractor
Moment frame base plates may require stiffener plates, adding significant shop time

What This Means for Estimating

When building a steel estimate, connection type drives your cost-per-ton more than almost any other factor. Here is a practical framework:

Step 1: Identify the lateral system — braced frame, moment frame, or both. This tells you where the expensive connections are.

Step 2: Count moment connections and brace connections individually. Do not lump them into a percentage.

Step 3: Apply appropriate shear connection costs to everything else.

Step 4: Add detailing/engineering costs — moment and brace connections require more detailing time per ton.

A tool like SteelFlo helps by letting you assign connection types per member and automatically adjusting the cost model, rather than applying a blanket connection percentage that may be too high or too low.

The bottom line: learning to read connections on structural drawings is one of the highest-value skills a steel estimator can develop. The difference between a $4,000/ton job and a $6,500/ton job is usually visible in the connection details — if you know where to look.