This section explains how Clariti calculates anchor channel capacity according to EN 1992-4. Understanding the methodology helps you interpret results and make informed design decisions.
Supported Products
Clariti supports the following cast-in anchor channel systems:
| Channel Family | Description | Anchor Diameter |
|---|
| CPRO38 | Light-duty channel | 8mm |
| CPRO50 | Medium-duty channel | 10mm |
| CPRO52 | Heavy-duty channel | 13mm |
Design Philosophy
Clariti follows the limit state design approach of EN 1992-4:
Where:
- NEd = Factored design load (input by you)
- NRd = Design resistance (calculated by Clariti)
The utilization ratio is:
A utilization ≤ 100% means the design is adequate for that failure mode.
Calculation Flow
For each connection, Clariti performs these steps:
- Validate inputs — Check bolt positions against constraints and verify channel/bolt compatibility
- Calculate influence length — Determine which anchors are affected by each load
- Distribute forces to anchors — Calculate how loads transfer to individual anchors
- Find worst-case loading — Identify the critical bolt position that maximises anchor forces
- Calculate resistances — Determine characteristic resistances (NRk, VRk) for each failure mode
- Apply safety factors — Convert to design resistances (NRd = NRk / γM)
- Calculate utilization — Compare demand to capacity (β = NEd / NRd)
- Check interaction — For combined loading, verify interaction equation
- Report results — Identify governing failure mode (highest utilization)
Failure Modes
Anchor channels can fail in multiple ways. Clariti checks all applicable failure modes per EN 1992-4 Table 7.4 and reports the governing one (highest utilization).
Tension Failure Modes
Per EN 1992-4:2018, anchor channels under tension must be verified against both steel and concrete failure modes.
Steel Failure Modes (Tension)
| Mode | Description | What It Checks |
|---|
| Anchor in tension | Fracture of anchor shaft | Anchor steel tensile capacity |
| Anchor channel connection | Failure of weld between anchor and channel | Connection strength |
| Channel lips | Local failure of channel lips | Lip bending capacity |
| Channel bolt | Fracture of the T-bolt | Bolt tensile capacity |
| Channel in bending | Flexural failure of channel | Channel bending moment capacity |
Concrete Failure Modes (Tension)
| Mode | Description | When Critical |
|---|
| Concrete cone | Breakout of concrete cone around anchor | Most common governing mode |
| Pullout | Anchor pulls out without full cone formation | Related to bearing area |
| Splitting | Concrete splits due to wedging action | Thin members, close edges |
| Blowout | Side breakout near edges | Anchors close to edges |
Shear Failure Modes
Per EN 1992-4:2018, anchor channels under shear must be verified against both steel and concrete failure modes.
Steel Failure Modes (Shear)
| Mode | Description | What It Checks |
|---|
| Anchor in shear | Shear fracture of anchor | Anchor shear capacity |
| Anchor channel connection | Failure of connection in shear | Connection shear strength |
| Channel bolt | Shear failure of T-bolt | Bolt shear capacity |
Concrete Failure Modes (Shear)
| Mode | Description | When Critical |
|---|
| Concrete edge | Breakout toward free edge | Loads acting toward edges |
| Pryout | Back-side concrete failure | Short, stiff anchors |
Combined Loading
When both tension and shear act simultaneously, Clariti checks interaction using EN 1992-4 equations. The combined utilization must also be ≤ 100%.
Partial Safety Factors
Material partial factors from ETA-13/0224:
| Failure Mode | γM | Notes |
|---|
| Steel — anchor | 1.85 | From ETA |
| Steel — channel | 1.8 | From ETA |
| Steel — bolt | 1.87 | From ETA |
| Concrete cone | 1.5 | Standard |
| Pullout | 1.5 | Standard |
| Splitting | 1.5 | Standard |
Clariti uses product-specific γM values from the ETA where available, which may differ from generic EN 1992-4 values.
Transparency
Every calculation in Clariti can be expanded to show:
- Reference — EN 1992-4 clause number
- Equation — The formula being applied
- Inputs — All values used with sources
- Factors — Each ψ and γ factor with justification
- Result — Step-by-step evaluation
This transparency allows you to:
- Verify calculations manually
- Understand why capacity is limited
- Explain results to checkers and approvers
- Learn the EN 1992-4 methodology
Further Reading
