Anchor Loads – Tension, Shear and Combined Loading

The loads acting on an anchor are a fundamental part of anchor selection and design. Their magnitude, direction and point of application determine how forces are transferred through the anchorage and into the base material.

Anchors may be subjected to tension, shear or a combination of forces. Understanding these loads is essential when selecting an anchoring system and assessing whether it can meet the requirements of the application.

Understanding the loads acting on an anchor

Anchoring applications can be subjected to different types of loading. The direction and combination of these forces influence both anchor selection and the way the anchorage must be designed.

Tension loads

Tension acts along the axis of the anchor and attempts to pull the fixing out of the base material. The resistance of the anchorage depends on factors including the anchor type, embedment depth, concrete condition, edge distance and strength of the base material.

Shear loads

Shear acts across the anchor, approximately at right angles to its axis. Shear resistance can be influenced by the anchor material and diameter, concrete strength, edge distance and the position at which the load is applied.

Combined tension and shear

In many real applications, anchors are subjected to tension and shear at the same time. These forces cannot always be considered independently because their interaction can influence the overall utilisation of the anchorage.

Bending moments and eccentric loads

When a force is applied at a distance from the surface of the base material, an eccentric load can create a bending moment in addition to tension or shear. This can change how forces are distributed between individual anchors in a connection.

Anchor loads at a glance

The three loading conditions below provide a simple overview of how forces can act on an anchoring system.

Static, dynamic and exceptional loads

The way a load changes over time can also affect the requirements placed on an anchoring system.

Static and quasi-static loads

Many anchoring applications are designed for static or quasi-static loads, where forces remain constant or change relatively slowly over time.

Dynamic loads

Dynamic loading can occur where forces vary repeatedly or rapidly, such as in machinery, lifting equipment or other moving systems. Anchors used in these applications must be suitable for the relevant loading conditions and supported by the appropriate technical assessment or test data.

Seismic and exceptional actions

Earthquakes, impacts and other exceptional events can place very different demands on an anchoring system. Where these conditions form part of the design requirements, anchors must be specifically assessed and designed for the applicable action.

What influences anchor load capacity?

An anchor does not have one universal load capacity. Its performance depends on the complete anchoring system and the conditions in which it is installed.

Important factors include:

• Anchor type, diameter and material
• Concrete or base-material strength
• Cracked or non-cracked concrete
• Effective embedment depth
• Edge distance
• Anchor spacing
• Thickness of the base material
• Tension, shear or combined loading
• Installation quality
• Environmental and service conditions
• Relevant product approval and design requirements

For this reason, published load values should always be considered together with the conditions under which those values apply.

How base material affects anchor loading

The strength and condition of the base material have a direct influence on the performance of an anchorage. Concrete strength, cracking and the position of the anchor within the concrete member can all affect the available resistance.

Other substrates such as solid masonry, hollow masonry and lightweight materials behave differently and may require different anchor systems and design methods.

Explore anchoring base materials >

Cracked and non-cracked concrete

Concrete can develop cracks where tensile stresses occur. These cracks can influence the behaviour and resistance of an anchor, particularly in structural applications.

Where cracked concrete is expected, the selected anchor must be suitable for use under those conditions and the anchorage should be designed accordingly.

Understand cracked and non-cracked concrete >

Possible anchor failure modes

Anchor design must consider not only the applied load but also the different ways in which an anchorage could reach its resistance limit.

Depending on the anchor system and loading conditions, relevant failure modes can include:

• Steel failure of the anchor
• Pull-out failure
• Concrete cone failure
• Concrete splitting
• Concrete edge failure under shear

The governing failure mode depends on the anchor, installation geometry, concrete condition and applied loads.

Why anchor spacing and edge distance matter

Anchors positioned close to one another or close to the edge of a concrete member may have a lower resistance than an isolated anchor installed with unrestricted spacing.

Anchor spacing, edge distance, embedment depth and member thickness therefore form an important part of structural anchor design and should be considered together with the applied loads.

Explore anchoring conditions >

Calculate anchor loads in accordance with EN 1992-4

For structural fastenings in concrete, anchor design involves more than comparing an applied load with a single product load value. The interaction between tension, shear, concrete condition, anchor spacing, edge distances, embedment depth and potential failure modes must also be considered.

The Fabory Anchor Calculator helps you design post-installed anchors for structural use in concrete in accordance with EN 1992-4. Enter the project geometry and applied loads to identify suitable anchoring solutions and assess the relevant design conditions.

• Assess tension and shear loading
• Calculate combined loading conditions
• Account for cracked and non-cracked concrete
• Consider anchor spacing and edge distances
• Assess fire and seismic design conditions
• Generate calculation reports for project documentation

Use the Fabory Anchor Calculator >

Anchor loads, approvals and design requirements

Structural anchor design should be carried out using the applicable design standard together with the performance data for the selected anchor.

For post-installed fastenings in concrete in Europe, EN 1992-4 provides the design framework, while product-specific performance and application conditions are provided by the relevant European Technical Assessment (ETA).

Design resistance should therefore be verified against the relevant loading conditions, failure modes and application requirements rather than by applying a general safety factor to a single published load value.

Explore more anchoring guidance

Continue exploring Fabory's technical anchoring guidance:

• Types of anchors >
• Anchoring base materials >
• Cracked and non-cracked concrete >
• Anchoring conditions >
• Practical anchor design >
• Explore all anchoring technical guidance >

Need help with an anchor calculation?

Anchor loading can become complex when combined forces, multiple anchors, restricted edge distances or structural design requirements are involved. Fabory's technical specialists can help you assess the application requirements and identify a suitable anchoring solution.

Contact our technical specialists >

Frequently asked questions about anchor loads

Find answers to common questions about tension, shear, load capacity and structural anchor calculations.