Nelson studs are headed steel shear studs (also called shear connectors or headed stud anchors) welded to the top flange of a steel beam, usually right through the metal deck. Once the concrete slab is poured around them, they lock slab and beam together so the two act as one stronger composite member.
“Nelson” is a brand name the trade uses generically; drawings usually say “headed shear studs.” Below: uses, sizes and specs, installation, inspection and safety.
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An editable form to book your shear stud and deck inspection before the pour, so the inspector, erector and concrete crew all work off the same date and scope.
What are Nelson studs used for?
Their main job is composite action. Under load, a slab wants to slide along the beam it sits on. Studs stop that slip by transferring horizontal shear, so beam and slab work as one section. That lets the engineer carry more load or use a lighter beam.
Headed studs also anchor embed plates cast into concrete walls and columns, so steel can be welded to the plate later.
Common sizes
Shear studs are typically cold-drawn low-carbon steel (ASTM A108), classed in AWS D1.1 as “Type B” headed studs with a specified minimum tensile strength of 65 ksi, the value AISC 360 uses in composite design.
| Diameter | Typical lengths (after weld) | Common use |
|---|---|---|
| 1/2″ | 2″ to 4″ | Embed plates, light composite work |
| 5/8″ | 2-1/2″ to 6″ | Embeds, lighter composite floors |
| 3/4″ | 3″ to 7″ | Most common for composite beams with metal deck |
| 7/8″ | 4″ and up | Heavier work, usually welded direct to steel |
With deck, the stud must stand well above the ribs and still have concrete cover over the head (AISC 360 sets the minimums), so a 3″ deck often pairs with a 4-1/2″ or 5″ stud. Studs shorten as they weld (burn-off), so confirm whether the drawing length is before or after welding when you order.
How Nelson studs are installed
Shear studs go in by drawn-arc stud welding, using a stud gun, a controller and a high-amperage DC power source. (Capacitor-discharge welding is a lighter process for small pins and studs on thin sheet.)
- Deck is laid, fastened and tight to the beam flange. Gaps are a leading cause of bad welds.
- Studs are laid out to the drawings, usually one or two per deck rib.
- The operator loads a stud and a ceramic ferrule (a ring that shields and shapes the weld) into the gun.
- The gun lifts the stud, draws an arc that burns through the deck and melts the stud end and flange, then plunges the stud in, all in under a second.
- Ferrules are knocked off and removed before the pour.
Through-deck welding works on light-gauge deck. Heavy galvanizing, moisture, paint or mill scale hurt the weld; heavier deck may need pre-punched holes.
Inspection and testing (AWS D1.1)
Stud welding has its own clause in AWS D1.1 Structural Welding Code – Steel. In general terms:
- Pre-production test: at the start of each shift or after a setup change, the first two studs are welded and bent about 30° from vertical. No cracking at the weld means production can start.
- Flash check: every stud should show a full 360° weld flash at the base.
- Field bend test: studs without full flash, or repaired by welding, are bent about 15° from vertical, away from the missing flash. Studs that pass can typically stay bent.
- Ring test: a hammer tap that rings suggests a good weld. It’s a field screen, not a code test.
Many jurisdictions also require special inspection of studs before the pour. Book it with an inspection request form and track reports in a consultant inspection report log.
Layout and spacing
Stud count and spacing come from the engineer’s composite design, often shown as a count per beam. AISC 360 sets minimum and maximum spacing, and the deck ribs control where studs can go. If the ribs don’t suit the layout or the count won’t fit, send an RFI before you weld.
Safety
A studded deck is a serious trip hazard. OSHA’s steel erection rule (29 CFR 1926.754) bars installing shear connectors on beam top flanges until the deck or another working surface is in place. Keep the deck clean, mark access routes and post trip hazard signs. Arc flash, hot ferrules and fire risk below the deck belong in a welding and cutting toolbox talk. Check your local jurisdiction for fall protection requirements on deck.
FAQ
Do you need a special welder for Nelson studs?
Yes. Shear studs need a stud welding gun and controller with a high-amperage DC power source, often a dedicated generator on site. A standard stick or MIG welder can’t do the lift-and-plunge cycle, although AWS D1.1 allows some repairs with fillet welds by a qualified welder.
What are the specifications for shear studs?
Most are AWS D1.1 Type B headed studs in low-carbon steel with 65 ksi minimum tensile strength, commonly 3/4″ diameter. The structural drawings give diameter, length, count and spacing, and AISC 360 governs the design rules.
Are Nelson studs and shear studs the same?
On site, yes. Shear stud, shear connector, headed stud and Nelson stud all mean the same part.
How do you test a Nelson stud weld?
Check for a full 360° flash, then bend-test per AWS D1.1, typically to about 30°. A sound weld bends without cracking at the base.
Are Nelson studs the same as Nelson bolts?
No. A “Nelson bolt” usually means a threaded weld stud, welded the same way but threaded for a nut.
Summary
Build studs to the drawings, weld to a clean, tight surface, inspect to AWS D1.1 before the pour and manage the trip hazard. For the bigger picture, read our guide to structural steel and controlling quality on the jobsite.
Related template: Request for Inspection Form
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