Concrete Undercut Anchors

Currently, they are different types of mechanical anchors available. However, concrete undercut anchors are the strongest, and they can resist much higher loads compared to the mechanical expansion anchors. That is the reason why this type of anchors are often utilised in structures such as water treatment, nuclear power plants, and power industries where failure often leads to catastrophic consequences and human safety is of great importance.

In general, the strength and suitability of concrete anchors to resist the transfer of any action load from the area of application are always decisive. When it comes to concrete capacity, any fixing can only be as excellent as the base materials it’s fixing in to. But how mechanical anchors transfer the action load from the area of application has significant effects on the concrete capacity to resist any action or load.


How the Undercut Anchors Work

As the name suggests, mechanical expansion anchors perform their duties by expanding into pre-drilled holes into the concrete. The expansion leads to friction that provides the strength and resistance to the load or tensile action. When tensile action is greater, it increases the horizontal forces which are needed more. High expansion forces result in high stress or compression zones in concrete, which affects how the concrete expansion anchors can resist the action.

The undercut anchors work differently. They perform their duties by developing a positive key into a self-cut or a pre-cut void inside the available concrete. In most cases, they either create their void and key into it as in the case of Liebig Ultra-plus BLS anchor, or they open out into some pre-cut voids as in Liebig Ultra-plus. They don’t depend on friction and expansion, which means that they do not lead to high stress or compression zone.

As a result, they’re able to take advantage of the concrete floor anchor capacity, making them resist even higher tensile loads or action. In addition to the normal tensile action loads, the reduction of the compression stress zones and the mechanical interlock in concrete make the undercut anchors manage all the action loads that are created in seismic, dynamic and shock as well as other conditions with high impacts.


The Installation Process

The installation process differs depending on the type of undercut anchors being utilized. For a split drive concrete anchor or a self-undercut anchor like Liebig Super-plus BLS, there’s no need for the special tools. The anchor itself creates the undercut. When the BLS anchor expands into the predrilled holes, all the keys at the bottom of the resulting expansion shield lead to voids at a certain or predetermined depth inside the available concrete.

The keys then lock into the voids to provide much-needed resistance to tensile action or loads.

features of liebig safetybolt

The Uses of the Undercut Anchors

These type of anchors perform well in non-cracked and cracked concrete anchors. They can do this as a result of positive keying action which is created during their installation process. Positive keying enhances the ability to maintain resistance as cracks in concrete expand or created.

Unlike expansion anchors concrete, the undercut anchors do not need any follow up expansion capability. This clearly shows why undercut anchors are used on structures located in areas where earthquakes are prone or where seismic qualification is a key consideration.

Application Benefits of the Undercut Anchors

As discussed previously, the way these anchors transfer the load or tensile action into the heavy duty anchors for concrete and boost the capacity to resist tensile actions offers increased load capabilities. This type of operation also leads to additional benefits.

Stress or low compressive forces in concrete means that the undercut anchors can be used closer to concrete edges and they can be installed along with other similar anchors as well as be used in the design of anchors in concrete. This reduces construction materials, allows for smaller baseplates and minimizes constriction costs, which leads to significant savings in overall installation expenses for any application.