The Working Principle of the Expansion Anchor Bolt

An expansion anchor bolt, as its name suggests is used to attach objects to walls and floors. It can be used in concrete or wood, as well as drywall.

The anchor's ends expand to grip the base material during installation. This prevents it from moving out of place. This type of fastener can also be found in double-ended versions.

The Bolt

Expansion anchor bolts can be used to attach a structural component to concrete. They're commonly used to connect different types of structures to a concrete surface, including walls and floors.

The working principle of the expansion anchor bolt is based on mechanical interlock between the fastener and the substrate into which it's inserted. This means that a wedge-shaped internal piece of the anchor is pulled or pushed, depending on the type of anchor, to force the outer part of the anchor against the substrate into which it's inserted. Cast-in-place expansion anchor bolt and post-installed are the main types. Both of these types can be installed in pre-drilled holes, but they differ in one key way: cast-in-place bolts are installed upside down with their head first.

The through bolt is another type of anchor bolt. This type of anchor uses an end fork that slowly pulls through a clasp. The anchor claps expand as the end fork pulls on the clasp.

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The Collar

Concrete and masonry have expansion anchors that are used to attach objects to walls, floors, and ceilings. Unlike traditional screws or nails which are often inserted into holes in the wall, expansion anchors expand during installation to grip the sides of a hole, thus holding the object in place.

During installation, the installer drills a hole in the desired location and inserts the expansion anchor by hand until the end is flush with the side wall of the hole. Once the anchor is firmly in place, it is then secured to the wall using a metal expansion type masonry fastener, steel concrete screw, or powder actuated fastener.

The expansion bolt is typically made from a rectangular strip of steel that has been stamped and rolled into a shape. This process allows the sleeve to slidably fit concentrically on the recessed shank segment of the bolt. The sleeve then has circumferentially attached, spaced wedging sections that extend from the collar portion towards the leading end. Each wedging section has a narrow neck portion connecting it to its collar portion.

The Nut

They are made of carbon steel and plated in yellow zinc, and come with the nut and washer needed to set them. 

​The expansion anchor t bolts works by inserting a screw into a hole in concrete or masonry and tightening it. The bolt expands as the nut is pulled upwards, which prevents it being pulled out.

The type of expansion anchor, the base material into which it is inserted and its depth (hef), load, edge distance, spacing between anchors, all affect its holding power. Regardless of the installation method, the dominant failure modes of mechanical anchors under tension loading are steel breakage, concrete breakout and pull-out/pull-through.

Strike anchors are available in 6 different diameters and several lengths to suit most fastening needs. 

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The Sleeve

The working principle of the expansion anchor bolt is a simple one: a nut is tightened, and the cone-shaped stud end is pulled into the expander sleeve, which then wedges outward to lock the sleeve drop-in anchor into place. These pre-assembled mechanical anchors are ideal for concrete and masonry base materials, and come in a variety of head profiles including acorn, hex, rod coupler and flat-head.

Sleeve anchors are available in a variety of lengths to meet your application needs and they are code listed for cracked and uncracked concrete projects. They can also be made from specialty alloys like AL6XN and Alloy 20, Duplex Stainless and Titanium for added strength and corrosion resistance.

Sleeve anchors are designed to withstand both shear and pressure. This makes them ideal for medium-duty to heavy-duty applications where side pressure or vibration is present. They are not recommended to be used with soft or mortared materials or areas that have been damaged.