Types of Concrete Anchor Bolts

If you are searching for what type of concrete anchor bolt is the right fit for your job, you came to the right place. There are many types of anchor bolts that function differently and are designed for a wide variety of applications. Continue reading to learn about the different types of anchor bolts, common applications they are used for, and the factors to consider when choosing the correct bolt.

What is an Anchor Bolt?

Anchor bolts are mechanical fasteners that attach and secure objects to concrete surfaces. One end of the anchor bolt is installed into the concrete and the other end is visible above the concrete. The end that is exposed is typically threaded for attaching equipment.

Anchor Bolt Uses

Anchor bolts are designed to make your life easier by securing structures in place. This includes structural and nonstructural equipment. These versatile bolts are used in many industries. Some of the common industries and applications include:

• Repairing a wide range of equipment, support establishments, and structural parts for the chemical, petrochemical, and oil and gas industries.
• Power and steel industry
• Construction industry
• Rail lines and airplane industry
• Pharmaceutical and food processing plants
• Nuclear industry

Types of Anchor Bolts

Anchor bolts are categorized into two types:

• Cast-in-place anchor bolts are cast directly into wet concrete, often called 'wet-set' anchor bolts. Once the concrete cures and hardens, the bolt becomes fully secured. This is the simplest yet strongest type of anchor bolt you can use. Common versions of cast-in place anchor bolts include L bolts and J bolts.

• Drop-in anchor bolts are installed into the concrete after the concrete has been poured and hardened, and commonly referred to as 'dry-set' or 'post-installed' anchor bolts. In order to install a post-installed anchor bolt, a pilot hole must be drilled into the concrete to the correct depth, after which the bolt may be screwed in. Common versions of drop-in anchors include wedge anchors and sleeve anchors.

1. Wedge Anchor Bolts

Wedge Anchor bolts are very common anchor bolts due to several factors. They are corrosion-resistant, easy to install, and are one of the strongest concrete anchors available. Wedge anchors are named after the wedges that open and expand at their base when it is tightened.

Male wedge anchors consist of two pieces. One piece is threaded at the top end while the other end consists of a mechanism that includes a clip and wedges. The clip and wedges expand between the stud and the walls of the concrete. Wedge anchors are a great choice when it comes to heavy load or heavy shear applications. Fasteners Plus offers zinc, galvanized, and stainless steel wedge anchors.

2. Drop-in Anchor Bolts

Drop-in anchor bolts feature a pretty simple design. This type of bolt is a female anchor that is placed in a pre-drilled hole in the concrete. The expander plug at the base of the anchor is set by using a setting tool. The setting tool is a steel rod with one end necked down. The necked-down portion of the tool is inserted into the drop-in anchor. It is designed to be tapped with a hammer until the lip of the anchor meets the lip of the setting tool.

This type of anchor is excellent for use with threaded rods to install electrical cable trays, HVAC ductwork, and pipes and heads for fire sprinklers.

3. L Bolts and J Bolts

Bent-bar anchor bolts are steel rods or bars that are bent into an L or J shape. L bolts and J bolts have threads on one end and the other end is bent or bowed. The end that is bent is inserted into the concrete during installation.

These heavy-duty foundation bolts are commonly used for applications including signposts, shafts, heavy hardware, tooling, and additional steel structures. L bolts and J bolts are intended to be used with compatible nuts and washers. 

4. Sleeve Anchor Bolts

Concrete sleeve anchor bolts are threaded bolts enveloped by an expander sleeve at the top end. The other end of the bolt has a nut and washer. This type of male anchor bolt is threaded through the fixture and into a pre-drilled hole in the concrete. When you turn the nut on the bolt, the bolt is pulled through the sleeve.

Simpson Strong-Tie Sleeve All Anchors are available in a wide variety of lengths, diameters, and head style configurations so you can be sure to find the right option for your specific application.

5. Strike Anchor Bolts

Strike anchor bolts, also known as hammer drive anchors or hammer drive pin anchors are commonly used to attach lightweight fixtures to solid concrete. This may include shelf brackets, conduits, and electrical boxes. This male anchor bolt is an impact expansion fastener that consists of a tubular body with a drive pin that extends from the tubular casing.

Once you insert the anchor bolt into the pre-drilled hole in the concrete, the head of the pin is driven further into the tube by striking it with a hammer. This expands the tube and creates a strong hold in the concrete. Strike anchor bolts are generally not removable after they have been installed into the concrete. 

 6. Split Drive Anchor Bolts

Split drive concrete anchors are male anchors that have an expanded base that is split. The split base is compressed as the bolt is hammered into the concrete. It maintains outward pressure on the walls of the hole, which gives it holding power. Split drive anchors are skillfully designed for light-duty anchoring to concrete, brick, or block. 

7. Lag Shield Anchors

Lag shield anchors are female anchors that are threaded on the inside and feature a ribbed, slightly tapered sleeve. For installation, simply insert the lag shield into the correct-sized pre-drilled hole in the concrete.

Next, you will insert a lag screw into the lag shield and screw it in. As you twist the lag screw in, it expands the sleeve and cuts its own thread. The outer thread of the shield expands against the concrete. Lag shields are excellent for applications where vibration may affect the connection. 

Which Anchor Bolt is Right for You? 

Additionally, when selecting any fastener for a job, there are many factors to consider. When you install a bolt into concrete, the goal is that the fastener will last a lifetime. To make sure that goal can be achieved, it is important to choose the option that is right for you. Factors to consider include:

• The anchor bolt hole size - as the diameter of the hole increases, so does the load capacity.
• Anchor bolt length - the deeper the bolt is installed into the concrete, the higher the load-bearing power is. 
• The base material of the object.
• The environment of the application - invest in a corrosion-resist option if there is a risk of corrosion occurring.
• The amount of weight the anchor can endure.
• Type of load - the holding capacity of an anchor bolt reduces with vibrating and shocking loads.
• The material strength of the anchor bolt.
• The type of concrete.
• The size and position of the fittings.
• Anchor spacing requirements.