A shear stud is a short steel pin, typically with a flat head on one end, that gets welded to a steel beam and embedded in a concrete slab above it. Its job is to lock those two materials together so they act as a single structural unit rather than two separate layers sliding past each other. This connection, called composite action, dramatically increases the stiffness and load-carrying capacity of a floor system compared to steel and concrete working independently.
How a Shear Stud Works
When a load pushes down on a concrete slab sitting on a steel beam, the two materials want to slide horizontally relative to each other. The concrete slab tries to shorten along its bottom face, while the top flange of the steel beam tries to stretch. Without something physically connecting them, that sliding (called slip) means each material carries the load on its own.
A shear stud prevents that slip. The steel shank resists horizontal shear forces through what engineers call dowel action, essentially acting like a peg holding two boards together. The flat head at the top provides anchorage inside the concrete, preventing the slab from lifting away from the beam. Together, these two mechanisms transfer forces back and forth between steel and concrete so the whole assembly bends as one piece.
Under increasing load, the base of the stud where it meets the steel flange yields first. As slip grows to just 1 to 4 millimeters, a plastic hinge forms near the stud’s root, and the stud begins working like a tiny diagonal strut braced against the concrete. If slip continues well beyond that range (20 to 40 millimeters), the surrounding concrete cracks and the hinge migrates upward. At that point, the connection is approaching its limit.
What Shear Studs Look Like
The most common shear stud is a headed stud connector: a round steel shank with a slightly wider, flat disc forged onto one end. Standard diameters are 3/4 inch (19 mm) and 7/8 inch (22 mm), though smaller and larger sizes exist. After welding, a typical stud stands about 3 to 4.5 inches (76 to 114 mm) tall, depending on the depth of the metal decking it needs to extend through. The stud must project far enough above the deck ribs to be fully embedded in solid concrete, with a minimum projection of about 1.5 inches (38 mm) above the rib for a 3-inch deck.
How Shear Studs Are Installed
Shear studs are attached using a process called drawn-arc stud welding. A specialized welding gun holds the stud against the steel flange, draws it back slightly to strike an electric arc, then plunges the stud into the resulting pool of molten metal. The entire weld cycle takes less than a second for smaller studs and just a few seconds for larger ones.
For studs larger than about 14 mm in diameter, a ceramic ferrule (a small ring-shaped collar) is placed around the stud before welding. This ferrule serves two purposes: it contains the molten weld pool so it doesn’t spill outward, and it traps metal vapor that acts as a shielding gas to protect the weld from contamination. After the weld solidifies, the ferrule is knocked off and discarded, leaving a clean fillet of metal at the stud’s base. In most commercial construction, studs are welded right through the steel deck sheeting that supports the concrete slab, which speeds up installation considerably.
Spacing and Placement Rules
Building codes set both minimum and maximum distances between shear studs along the length of a beam. The maximum spacing allowed by the American Institute of Steel Construction (AISC) specification is 32 inches (about 810 mm), though in practice the largest spacing that satisfies all design checks is typically around 24 inches (610 mm). When the total slab thickness is less than 4.5 inches, a tighter limit of eight times the slab thickness controls the maximum spacing instead.
Minimum spacing prevents studs from being so close together that the concrete between them can’t develop full strength. Studs also need adequate concrete cover on all sides to ensure the bond holds. The number of studs placed along a beam depends on the shear force that needs to be transferred. A designer calculates the total horizontal shear between the point of maximum moment and the nearest support, then divides by the capacity of a single stud to determine how many are needed in that stretch. Partial composite action, using fewer studs than the theoretical maximum, is common and can be more economical while still providing significant stiffness gains.
How Shear Connections Fail
There are two broad categories of failure. In steel failure, the stud itself fractures. This happens when the concrete is strong and well-confined relative to the stud’s capacity, so the stud shears off at its base before the concrete gives way. Steel failure tends to be somewhat ductile, meaning the connection deforms visibly before breaking.
In concrete failure, the surrounding concrete gives out first. The most recognized form is concrete breakout (sometimes called concrete cone failure), where a cone-shaped chunk of concrete pulls away around the stud. This is the most common failure mode for studs installed at shallow depths. Other concrete-side failures include pull-out, where the stud slides out of the concrete without forming a clean cone, and side-face blowout, where concrete near the edge of a slab spalls outward. These non-breakout failures become more likely at deeper embedment depths or near slab edges. Concrete failures are generally more brittle than steel failures, which is why codes build in safety margins for concrete-controlled designs.
Quality Control and Testing
Every shear stud weld on a project gets a visual inspection. Inspectors look for a full 360-degree fillet of weld metal around the stud base, proper stud height, and no visible cracks or voids. Beyond visual checks, a common field test is the bend test: the inspector strikes or bends the stud to roughly 15 degrees from vertical. If it bends without cracking at the weld, it passes. Studs that fail are replaced.
The governing standard in the United States is AWS D1.1, the Structural Welding Code for Steel, which dedicates an entire clause (Clause 9) to stud welding. The most recent 2025 edition added new provisions for a category called type D studs and updated inspection acceptance criteria. The standard also spells out manufacturer qualification requirements for the studs themselves, ensuring the base material meets minimum tensile and yield strength thresholds before it ever reaches a job site. AWS D1.1 operates on a five-year revision cycle, so the next update would follow around 2030.
Where Shear Studs Are Used
The most common application is in composite floor systems in steel-framed buildings, where shear studs connect wide-flange beams to concrete slabs poured over corrugated metal decking. This is standard practice in commercial construction, from office towers to parking garages. Composite action lets engineers use lighter, shallower beams for the same span and load, which saves steel and can reduce overall building height.
Shear studs also appear in composite bridge decks, where they connect steel girders to a reinforced concrete driving surface. In bridges, the studs endure millions of load cycles from traffic, so fatigue performance becomes a critical design consideration on top of static strength. Other applications include anchoring steel plates to concrete walls and connecting steel columns to concrete foundations, though headed studs in those roles are often called anchor studs rather than shear studs.