What are Shear Studs and Why are They Essential in Composite Construction?

Shear studs line the surface of a steel beam, integral to forming sturdy and long-lasting composite structures.

Shear studs are small but critical components of composite construction, a building method that integrates two or more dissimilar materials to form a single structural unit that acts as one.

This is most commonly done to steel and concrete and requires a method that leverages the complementary strengths of the different materials. In this case, it combines the tensile strength of steel with the compressive strength of concrete to create structures that are stronger, more efficient, and more durable than those made from each material alone.

This article covers the function of shear studs, where it is used, the benefits, and how to install them in composite structures

What are Shear Studs?

Shear studs are metal studs welded to the top flange of steel beams in composite construction.

Their primary purpose is to enhance the strength and stiffness of the combined steel by providing a shear connection that ensures the concrete slab and steel beam act together as a robust unit.

Made of durable material such as Grade C-18 mild steel, shear studs have enhanced load-bearing capacity, increased stiffness, and material efficiency.

Grade C-18 mild steel, in particular, has a good strength-to-weight ratio and is known for good weldability and machinability. Its low carbon content provides a good balance of strength and ductility, with sufficient toughness for many structural applications.

Key Benefits of Using Shear Studs

Shear studs are essential in creating efficient, durable, and safer composite structures. Some of the key benefits include the following:

• Enhanced structural integrity. Shear studs provide a strong mechanical connection between steel beams and concrete slabs, enabling them to act together as a single unit, which improves the strength and stiffness of the composite system.

• Improved load distribution. By transferring shear forces between steel and concrete, the shear studs prevent the individual pieces from slipping. This ensures uniform load sharing, enhancing the composite’s load-bearing capacity and stability.

• Better cost savings. Shear studs enable the use of composite construction techniques that reduce material consumption, like excess steel reinforcement, resulting in cost savings on materials and labor. They also speed up construction timelines by simplifying assembly.

• Increased structural durability. Shear studs prevent the movement between steel and concrete, helping to minimize deformation and wear. They extend the lifespan of buildings, bridges, and industrial structures even in harsh environments.

• Improved resilience. Shear studs enhance the durability of structures against lateral forces, such as wind and earthquakes. They make buildings safer and more robust in seismic zones.

When and Where are Shear Studs Used?

Below are some cases where shear studs are used:

• Bridge decks and overpasses. In composite bridge construction, shear studs connect steel girders to concrete bridge decks, ensuring effective load transfer and preventing separation under traffic loads.

• Multi-level buildings and high rises. Shear studs are extensively used for load transfer in large-scale construction projects with composite steel and concrete elements.

• Pre–cast concrete connections. Shear studs simplify the connection between beams and concrete slabs or walls. They replace complex corbels or mechanical fasteners with a welded steel-to-concrete interaction.

• Movement and expansion joints. Shear studs are used at movement joints in slabs and frames to transfer shear forces while allowing some controlled movement, such as in suspended floor slabs, movement joints in framed buildings, and carriageway joints.

• Industrial mezzanines and platforms. Shear studs are welded directly onto structural beams, girders, or plates. Next, a concrete slab is poured over the metal decking that rests on these studs. The studs embed into the concrete, creating a strong mechanical interlock.

How are Shear Studs Installed?

Shear studs are typically installed through a process called stud welding. It’s fast, efficient, and produces high-strength connections compatible with structural workloads. It is often done on-site with portable stud welding equipment.

Equipment and Materials for Installing Shear Studs

The following equipment and materials are often used to install shear studs, usually via stud welding:

• Stud welding gun: a special handheld device used to perform the stud welding process. It generates the electric arc needed to weld the shear stud to the steel surfaces. The gun also applies the necessary pressure to plunge the stud into the molten weld pool.

• Shear studs: fasteners with an upset (headed) end for mechanical interlock with concrete. They vary in diameter and length, based on structural requirements.

• Ceramic ferrules (rings): used in drawn arc stud welding to contain the molten pool, shield the weld area from atmosphere contamination, and control weld quality. The ferrule surrounds the stud base during welding and is fractured after cooling.

• Ground clamp and cable: essential for completing the electrical circuit during welding. It is securely attached to the base metal near the weld location.

• Surface preparation tools: wire brushes or grinders. These tools are used to clean the surface for optimal weld quality before stud installation.

  
  

How to Install Shear Studs

Follow these steps to create a composite action between your steel material and concrete slab.

1. Prepare the base metal. Start by cleaning the surface where the studs will be installed. Use wire brushes or grinders to remove dirt, rust, oil, or paint to ensure proper welding.

2. Position the stud. Place the shear stud on the steel surface. Their heads and shanks are designed to be welded onto the surface.

3. Use the ceramic ferrule. Fit the ceramic ferrule around the base of the shear stud to create a contained chamber that holds the molten metal pool formed during welding.

4. Trigger the arc. Use the stud welding gun to generate an electric arc between the stud base and the steel surface. This melts the base of the stud and the steel surface to create a molten pool. The stud is then plunged into this molten pool and held while it cools and solidifies, forming a strong metallurgical bond.

5. Inspect the studs. After welding, inspect and test the studs to ensure weld quality. Use non-destructive methods, like ultrasonic or bend tests.

6. Pour the concrete. Once all the shear studs are installed and inspected, pour the concrete over the decking beam or flange. This embeds the weld studs in the concrete to develop composite action.

Common Mistakes When Installing Shear Studs and How to Avoid Them

Installing shear studs requires careful preparation and work. Be sure to avoid the following mistakes when installing them.

Improper Surface Preparation

Welding shear studs onto dirty, rusty, oily, or painted steel surfaces leads to poor weld quality and weak bonds. Be sure to clean the base steel flange or decking before welding.

Misalignment or Incorrect Stud Spacing

Misaligned, incorrectly placed, or unevenly spaced studs reduce composite action efficiency and load transfer. Use accurate layout marks and follow design specifications.. Always measure carefully to ensure correct positioning.

Poor Welding Technique

Inadequate weld time, wrong power settings, and even improper weld gun handling can result in incomplete welds or stud detachment. Always check the equipment settings and even calibrate if necessary. Be sure to verify weld parameters for the correct stud size and material.

Ignoring Environmental Factors

High humidity, rain, and extreme cold can negatively impact weld quality. Schedule welding when the weather is favorable or take protective measures by conducting the process in a heated environment.

Skipping Inspection after Installation

Failing to inspect welds visually or conduct end tests means risking unnoticed defects. Be sure to implement routine weld inspection and testing protocols as per standards.

Choosing the Right Shear Studs

Choosing the right shear studs involves considering several key factors to ensure the studs perform optimally for the specific composite construction project.

Load Requirements

Shear studs must be selected based on the expected shear focus and loads of the composite beam or slab. Higher loads demand studs with larger diameters, greater strengths, or increased quantity for adequate shear transfer.

Stud Size and Length

Shear stud diameters typically range from 10 mm to 22 mm, with lengths typically from 50 mm to 150 mm. A stud’s appropriate length depends on the concrete slab thickness to ensure full embedment for a strong band. Diameter, on the other hand, depends on load capacity.

Head style: full vs. reduced

Shear studs have different head types, primarily categorized as full head (standard or normal) and reduced-based types.

Full head shear studs have a full, mushroom-shaped or rounded head with a diameter larger than the shank. Full heads provide a large bearing surface embedded in the concrete, which enhances the mechanical interlock and shear transfer. They are commonly used in composite construction because they provide reliable strength and are well-suited for standard steel-to-concrete bonding.

Reduced base shear studs, on the other hand, have a smaller or reduced diameter head compared to the full head. They are used where space is limited or in specialized designs where less concrete coverage or lower head protrusion is necessary. They may also be used in retrofit applications or thin slabs where a smaller head reduces the risk of the concrete cracking.

Material Properties

Studs are usually made from low-carbon or high-strength steel to provide the required tensile strength and weldability. Environmental exposure is another factor and requires stainless steel or coated studs for corrosion resistance.

The Bottom Line of Shear Studs

In summary, shear studs are a critical component in the construction industry. They are versatile and effective, especially in composite construction.

If you’re looking for top-quality shear studs for your next construction project, go with trusted suppliers like Stanhope.

Order your shear studs in bulk now.

Shear Stud with Ceramic Ferrule

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