Shear Stud Connectors: Specifications, Design Resistance and Stud Welding

Quick Answer

Shear stud connectors are headed steel studs welded to the top flange of a steel beam and cast into the concrete slab above. They carry the longitudinal shear between steel and concrete so the two work as one composite section, typically doubling the beam's resistance and up to tripling its stiffness. Studs are specified to EN ISO 13918 type SD, or AWS D1.1 Type B in US practice, in diameters of 10 to 25 mm; 19 mm is the usual building size, and the common stud steel has a minimum tensile strength of 450 MPa (65 ksi). They are fixed by drawn-arc stud welding inside a ceramic ferrule, straight to the beam or through galvanised profiled decking, which EN 1994-1-1 allows for studs up to 20 mm. Under EN 1994-1-1, design resistance is the lower of 0.8 fu πd²/4 ÷ γV (shank) and 0.29 α d² √(fck Ecm) ÷ γV (concrete), with a recommended γV of 1.25: about 82 kN for a 19 × 100 mm stud in C30/37 concrete. Decking multiplies this by a factor kt of at most 0.85 for one through-deck stud per trough in sheet up to 1 mm thick. Welds are checked for a full 360° collar and by ring and bend tests.

A typical shear stud enquiry reads: "Shear studs 19 × 100, 8,000 pieces, with ferrules." Is 100 mm the length before or after welding? Will the studs be welded straight to the beam or through decking, which changes the ferrule and the finished length? Which standard and stud steel, and which certificates will the engineer ask for?

Studs are cheap per piece and expensive to get wrong: a short, badly welded or wrongly spaced stud weakens the floor it was meant to stiffen. This guide covers how shear studs work and how they are specified, designed, welded, tested and ordered.

What Shear Studs Do

Without a connection, a steel beam and the slab on it slide over each other and each carries load on its own. Shear studs stop that slip by transferring longitudinal shear at the interface, so the slab becomes the compression flange of a composite T-section and the steel works mainly in tension. UK steel design guidance puts the gain at around twice the bare beam's resistance and up to three times its stiffness, less on long spans.

Three properties matter:

• Strength: stud resistance times the number of studs between a support and the point of maximum moment sets the force transferred
• Ductility: studs deform before failing, so load redistributes between them; EN 1994-1-1 treats a connector with a characteristic slip capacity of at least 6 mm as ductile, and headed studs at least 4d long after welding qualify within limits on the degree of shear connection
• Uplift resistance: the head anchors the stud in the concrete; EN 1994-1-1 asks connectors to resist a nominal tension of at least 0.1 times their design shear resistance

With fewer studs than full shear connection needs, the beam has partial shear connection: the most common case in buildings, because decking trough spacing limits how many studs fit.

Headed Stud Geometry and Standards

EN ISO 13918 type SD

EN ISO 13918 (Welding — Studs and ceramic ferrules for arc stud welding) classes shear connectors as type SD: drawn-arc studs welded with a ceramic ferrule (types UF or DF) or shielding gas.

US Type B studs come in 3/8 to 1 in (9.5–25.4 mm) diameters. Every SD head is at least 1.5d across and 0.4d deep, the minimum EN 1994-1-1 sets for a stud head.

Stud steel

• SD1 (EN ISO 13918): non-alloy stud steel with a carbon equivalent of 0.38 maximum, for weldability. UK bridge design guidance gives the strength of the higher-grade stud as 450 N/mm²
• SD3 (EN ISO 13918): stainless steel studs, with materials to ISO 15510
• AWS D1.1 Type B (US): cold-drawn carbon steel with minimum tensile strength 65 ksi (450 MPa), yield strength 51 ksi (350 MPa), 20% elongation in 2 in and 50% reduction of area

EN 1994-1-1 caps the fu used in design at 500 N/mm² in solid slabs and 450 N/mm² in decking with ribs across the beam, so stronger stud steel earns no extra design resistance.

Length before and after welding

Studs shorten in welding as the tip and some parent metal melt into the collar: UK bridge guidance cites a 19 mm stud 125 mm long before welding and typically 120 mm after, and through-deck studs finish about 5 mm shorter again in one maker's data. Order by length after welding, which must give at least 3d overall and, in decking, 2d above the deck.

How Drawn-Arc Stud Welding Works

Drawn-arc stud welding fixes a stud from one side, with no hole:

1. The gun holds the stud against the flange inside a ceramic ferrule, lifts it slightly and draws an arc
2. The arc melts the stud tip and a pool in the parent metal
3. The gun plunges the stud into the pool; the ferrule contains the molten metal, shields the arc and shapes a collar around the base
4. The ferrule is broken off, leaving a full 360° collar on a sound weld

Current and arc time are pre-set for the stud and adjusted on site, where weather, parent steel and cable length all affect the result.

The welding standard is EN ISO 14555 (Welding — Arc stud welding of metallic materials), covering procedure and operator qualification and production testing; its 2025 edition replaced the 2017 edition. EN 1994-1-1's stud resistances assume studs automatically welded to it. In US practice the stud welding clause of AWS D1.1 applies (Clause 7 in older editions), with AWS D1.5 for bridges.

Through-deck welding

In most composite floors, studs are welded through the profiled decking into the beam flange, fixing both in one operation. The conditions:

• Stud size: EN 1994-1-1 limits through-deck studs to 20 mm; one US evaluation report allows studs up to 19 mm (3/4 in) through one deck layer up to 1.61 mm (16 gauge) with galvanising up to G90 (275 g/m²), or two such layers with up to G60 (180 g/m²)
• Deck: typically about 1 mm thick; UK guidance states that galvanising on the deck does not affect weld quality
• Top flange: unpainted and relatively clean, with no weldable primer, galvanising, excessive rust, mill scale or dirt, under the BCSA code of practice for metal decking and stud welding (UK)
• Weather: no welding when water cannot be kept off the deck, or below freezing
• Power: the BCSA code describes a dedicated 150 A, three-phase, 415 V mains supply, where one is available, or a generator, with welding and control cable no longer than 80 m
• Ferrules: through-deck ferrules differ from those for welding straight to steel

Design Resistance to EN 1994-1-1

EN 1994-1-1:2004 (clause 6.6.3.1) gives the design shear resistance of an automatically welded headed stud in a solid slab as the lower of:

• Shank failure: PRd = 0.8 fu π d²/4 ÷ γV
• Concrete failure: PRd = 0.29 α d² √(fck Ecm) ÷ γV

where d is the shank diameter (16 to 25 mm), fu the stud's specified ultimate tensile strength (not more than 500 N/mm²), fck and Ecm the concrete's characteristic cylinder strength and mean modulus, hsc the stud's overall height, and α = 0.2 (hsc/d + 1) for 3 ≤ hsc/d ≤ 4, or 1.0 where hsc/d > 4. The recommended γV is 1.25; check the National Annex. The second-generation revision has reviewed the stud model, so confirm the edition the project uses.

Reduction for profiled decking

With decking, the concrete around a stud is confined to the trough, so the solid-slab resistance is multiplied by a reduction factor:

• Ribs parallel to the beam: kl = 0.6 (b0/hp)(hsc/hp − 1) ≤ 1.0
• Ribs across the beam: kt = 0.7/√nr × (b0/hp)(hsc/hp − 1) ≤ kt,max, for ribs up to 85 mm deep with b0 ≥ hp, and fu taken as no more than 450 N/mm²

Here b0 is the mean trough width, hp the deck height and nr the number of studs per trough; EN 1994-1-1 takes nr as no more than two, and UK guidance allows no more than two studs per trough.

Worked example: studs for a secondary beam

A secondary beam carries a composite slab on 60 mm trapezoidal decking, 0.9 mm thick, with a mean trough width b0 of 150 mm and troughs at 300 mm centres. The concrete is C30/37, and the studs are 19 mm, 100 mm high after welding, with fu = 450 N/mm², welded through the deck.

Solid-slab resistance

• hsc/d = 100/19 = 5.3, above 4, so α = 1.0
• Shank: 0.8 × 450 × π × 19²/4 ÷ 1.25 = 81.7 kN
• Concrete, with fck = 30 MPa and Ecm = 33,000 MPa from EN 1992-1-1: 0.29 × 1.0 × 19² × √(30 × 33,000) ÷ 1.25 = 83.3 kN
• PRd = 81.7 kN (about 18.4 kips), so the shank governs. In C25/30 (Ecm = 31,000 MPa) the concrete term drops to 73.7 kN and governs instead

Decking checks and reduction

• Checks: stud 100 − 60 = 40 mm above the deck (≥ 2d = 38 mm); hp = 60 mm ≤ 85 mm; b0 = 150 mm ≥ hp
• One stud per trough: kt = 0.7 × (150/60) × (100/60 − 1) = 1.17, capped at 0.85, so each stud gives 0.85 × 81.7 = 69.4 kN
• Two studs per trough: kt = 0.7/√2 × 2.5 × 0.667 = 0.82, capped at 0.70, so each gives 57.2 kN and the pair 114.3 kN. The second stud adds only about 65% of the first, and the pair must be at least 4d = 76 mm apart

How many studs?

Say the beam design calls for 1,200 kN of longitudinal shear between the support and midspan of a 9 m span.

• Full shear connection with one stud per trough: 1,200 ÷ 69.4 = 17.3, so 18 studs
• But a 4.5 m half-span has only 4,500 ÷ 300 = 15 troughs. Fifteen single studs give 15 × 69.4 = 1,041 kN, an 87% degree of shear connection
• Doubling the studs in four troughs gives 11 × 69.4 + 4 × 114.3 = 1,221 kN from 19 studs: full connection

An 87% connection may be acceptable if it meets the code's minimum degree of shear connection for the span and steel grade. Check the flange too: under EN 1994-1-1 a stud's diameter should generally not exceed 2.5 times the thickness of the plate it is welded to, so a 19 mm stud needs a flange at least 7.6 mm thick.

Detailing Rules

Bridges follow EN 1994-2, where the fatigue resistance of the shear connection must also be checked.

Inspection and Testing

UK practice follows the BCSA code of practice for metal decking and stud welding:

• Before welding starts, and whenever the equipment is moved or changed: weld at least two test studs and bend them 30° from their axis; if a weld fails, adjust the settings and repeat
• Every stud, visually: a full 360° weld collar. A stud without one is bent 15° from vertical, and studs that fail are replaced
• Ring test: struck with a hammer, a sound stud gives a clear ring; a dull sound suggests a defective weld
• Production bend tests: at least 5% of the studs, and no fewer than two per beam; if one fails, the studs either side are tested

US practice under AWS D1.1 is similar. One US federal guide specification calls for bend or torque tests, to AWS D1.1, on one stud in every 100 and on any stud without a full 360° flash, repaired by welding or shortened less than normal; each failure triggers two more tests, and if either fails, all the studs represented are rejected.

Shear Studs, Anchors and Threaded Studs

• Shear studs connect a steel beam to the slab it supports and are designed to EN 1994 (composite structures)
• Embedded plates with headed anchors are cast into concrete as fixing points; their anchors are designed for concrete cone, pull-out and edge failures under EN 1992-4 or ACI 318, not as composite connectors
• Anchor bolts hold column bases and equipment to foundations; see our guide to anchor bolts
• Threaded studs (EN ISO 13918 types such as PD and RD) are welded the same way but take a nut for a bolted fixing. Some catalogues also use "shear stud bolt" for threaded studs and rods, so confirm whether a headed SD connector or a threaded stud is meant

Ordering Checklist

• Standard and type: EN ISO 13918 type SD or AWS D1.1 Type B, and the design code
• Diameter and length: for example 19 × 100 mm, stating whether the length is before or after welding
• Welding method: through deck or straight to steel, with the deck profile and thickness
• Material: SD1 carbon steel or SD3 stainless, and the minimum tensile strength
• Ferrules: type and quantity matched to diameter and welding method
• Quantity: studs per beam × beams, plus test studs (at least two per start-up or equipment change under the BCSA code) and spares
• Site welding: who welds, the power available, and procedure qualification to EN ISO 14555 or AWS D1.1 (see our guide to WPS, PQR and welder qualification for the principles)
• Drawings: beam layout, stud positions and spacing, deck orientation
• Documents: material certificates to EN 10204 3.1 (see material test certificates), welding procedure and test records

Common Mistakes

1. Ordering length without saying before or after welding. Studs lose several millimetres in welding, more through deck, so the finished height can fall below 3d, or below 2d above the deck.

   Prevention: Specify length after welding, and confirm the length before welding with the supplier.

2. Welding studs over 20 mm through decking. EN 1994-1-1's through-deck rules stop at 20 mm.

   Prevention: Use 19 mm studs through deck; for larger studs, use pre-punched decking (up to 22 mm) or shop-weld the studs and fit the deck around them.

3. Painted or galvanised top flanges. Primer, galvanising, mill scale and heavy rust on the flange spoil the weld.

   Prevention: Keep the top flange unpainted where studs go, and say so on the steelwork drawings.

4. Welding in the wet or the cold. Water on the deck and sub-zero temperatures produce defective welds.

   Prevention: Stop when water cannot be kept off the deck or the temperature is below freezing.

5. Expecting a second stud per trough to double the capacity. In the worked example the second stud adds about 65%, and two per trough is the practical limit.

   Prevention: Check kt for the actual number of studs per trough, and consider partial shear connection.

6. Skipping start-up tests. Yesterday's settings can fail today with different weather, cable length or steel.

   Prevention: Weld and bend-test studs at every start-up and after any change of equipment.

7. Confusing threaded "shear stud bolts" with headed shear connectors. A threaded stud has no head to anchor it in the slab and is not designed as a composite shear connector.

   Prevention: Specify EN ISO 13918 type SD or AWS D1.1 Type B headed studs, with the head size.

Supply from Kasko Makine

Kasko Makine supplies stud fasteners for steel and composite construction:

• Stud nails, welded and embedded anchors — headed or headless stud nails for shear transfer, welded studs attached to steel by stud welding, and embedded anchors cast into concrete as fixing points. Carbon steel, alloy steel or stainless steel (on request), with plain (black), zinc-coated, hot-dip galvanised or custom finishes, for steel–concrete composite floors, bridges and infrastructure, industrial buildings and plants, precast and cast-in-place concrete, and anchoring machinery and equipment
• Shear stud bolts — threaded studs for load transfer, anchoring and shear resistance, threaded over their full or partial length, in carbon, alloy or stainless steel and in standard and custom sizes, for structural steel connections, construction anchoring systems, industrial machinery, power plants and oil, gas and petrochemical facilities

Engineering support: Send the beam layout, deck profile, stud diameter and length after welding, and the welding method. We will review the stud specification against your data and quote the studs for your project.

Send the stud diameter, length after welding, welding method, quantity and certificate requirements for a quotation — we reply within 24 hours. Reach us at info@kaskomakine.com or WhatsApp +90 (537) 521 1399.

Continue Reading

• Railway Rails: Flat-Bottom, Bullhead and Double-Headed Rails, Profiles and Grades
• Anchor Bolts: Types, Specifications and Applications
• Industrial Fasteners: Stud Bolts, Hex Bolts, Nuts and Washers
• WPS, PQR and Welder Qualification to ASME Section IX
• Carbon Steel Plate: ASTM A516 and A36
• Plant Construction and Erection Equipment

Frequently Asked Questions

Q: What is a shear stud connector?
A: A shear stud connector is a headed steel stud welded to the top flange of a steel beam and cast into the concrete slab above. It transfers longitudinal shear between steel and concrete so the two act as one composite section, typically doubling the bare beam's resistance and raising its stiffness up to threefold. The head anchors the stud against uplift.

Q: What size shear studs are used in composite beams?
A: EN ISO 13918 type SD studs come in shank diameters of 10, 13, 16, 19, 22 and 25 mm, and the EN 1994-1-1 design formulae cover 16 to 25 mm. The 19 mm stud is the usual size in buildings and can be welded through steel decking, which the Eurocode limits to studs of 20 mm or less; overall height must be at least three diameters.

Q: How is the design resistance of a shear stud calculated?
A: EN 1994-1-1 takes the lower of two values: shank failure, 0.8 fu π d²/4 divided by γV, and concrete failure, 0.29 α d² √(fck Ecm) divided by γV, with γV recommended as 1.25. For a 19 mm stud 100 mm high with fu of 450 N/mm² in C30/37 concrete, the shank governs at about 81.7 kN. In profiled decking the result is multiplied by a reduction factor.

Q: Can shear studs be welded through steel decking?
A: Yes. Through-deck welding is the usual method in composite floors: the arc melts through the galvanised deck and the stud welds to the beam flange beneath. EN 1994-1-1 covers through-deck welded studs up to 20 mm diameter. The top flange must be unpainted and clean, and welding stops when water cannot be kept off the deck or below freezing.

Q: How are welded shear studs tested?
A: Under the UK BCSA code, at least two test studs are welded and bent 30 degrees before work starts or after any equipment change. Every stud is checked for a full 360-degree weld collar; any without one is bent 15 degrees and replaced if the weld fails. Production bend tests cover at least 5 percent of studs, and no fewer than two per beam, with a hammer ring test as a quick check.

Q: What is the difference between stud length before and after welding?
A: A stud shortens during welding because its tip and part of the parent metal melt to form the weld collar. A 19 mm stud 125 mm long before welding is typically about 120 mm after, and through-deck studs finish about 5 mm shorter again in one maker's data. Orders should state length after welding, since the code's minimum heights apply to the finished stud.

Q: What material are shear studs made from?
A: Standard studs are carbon steel. EN ISO 13918 type SD1 steel has a carbon equivalent of 0.38 or less for weldability, and UK guidance gives 450 MPa as the higher-grade stud strength. AWS D1.1 Type B studs need at least 450 MPa tensile and 350 MPa yield strength, 20 percent elongation and 50 percent reduction of area. Stainless steel SD3 studs are used in corrosive conditions.