Concrete Pryout Failure can occur when short stiff anchors are loaded in shear. Pryout failure is caused by the rotation of the anchor and the catenary tension forces generated in the anchor bolt as a result of the lateral deformation and the eccentricity between the acting shear force and the resultant resisting force in the concrete. This is illustrated in the below diagrams. This mode of failure can occur for cast in anchors, mechanical anchors or chemical anchors. The CivilWeb Concrete Anchorage Design Spreadsheet completes all the concrete pryout failure calculations detailed below for cast in anchors, mechanical anchors and chemically bonded anchors in accordance with BS EN 1992-4.

## Concrete Pry Out Failure **Design Verification Calculations**

To avoid concrete pryout failure the Design Concrete Pryout Failure Resistance (V_{Rd, cp}) must be greater than or equal to the Design Shear Force (V_{Ed}), as shown in the below equation.

**Partial Safety Factor for Concrete Pryout Failure (***γ*_{Mc})

*γ*

_{Mc})

This is the partial factor of safety applied to concrete failure. A value of 1.5 is typically recommended.

**Characteristic Pryout Failure Resistance (V**_{Rk, cp})

_{Rk, cp})

For cast in anchors and mechanical anchors this can be calculated using the below equation;

### Characteristic Resistance to Concrete Cone Failure (N_{Rk,c})

The characteristic resistance to concrete cone failure is detailed here.

### Characteristic Resistance to Combined Concrete Cone and Pull-Out Failure (N_{Rk,p})

The characteristic resistance to combined concrete cone and anchor bolt pull out failure is detailed here.

### Effective Depth Factor (k or k_{3})

This factor depends on the effective depth of the anchor. This can be taken from the manufacturer’s info. If this is not available the following equation can be used as a conservative guide;

### Effective Depth (h_{ef})

This is the effective depth of the anchor.

## Concrete Pryout Failure - CivilWeb Concrete Anchorage Design Spreadsheet

Concrete pryout failure can be a critical design verification in cases where the a short anchor includes significant shear loading. In these cases the CivilWeb Concrete Anchorage Design Spreadsheet completes all the above detailed calculations in accordance with BS EN 1992-4 in order to complete the design verification check. The spreadsheet includes unique features including our design graphs which make using this spreadsheet the quickest and easiest way to complete detailed and fully compliant concrete anchorage designs.

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