Tension Verification

This page explains how Clariti verifies anchor channels against tension failure modes according to EN 1992-4.

Overview

Four tension failure modes must be checked:

Steel failure — Fracture of anchor or channel steel
Concrete cone failure — Breakout of concrete cone
Pullout failure — Anchor pulls out without cone formation
Concrete splitting — Splitting of concrete member

Each mode has characteristic resistance (NRk) reduced by partial factors (γM) to give design resistance (NRd).

Verification Format

All verifications follow the same format:

βN = Nᵃₑd / NRd ≤ 1.0

Where:

βN = Utilisation ratio (shown as percentage)
Nᵃₑd = Design tension force on anchor (from force distribution)
NRd = Design resistance for the failure mode

A utilisation ≤ 100% means the design is adequate for that failure mode.

Steel Failure — Anchor in Tension

This failure mode occurs when the tension load exceeds the tensile strength of the anchor shaft, causing it to fracture.

Equation

NRd,s,a = NRk,s,a / γMs

Parameters

Symbol	Description	CPRO38	CPRO50	CPRO52	Source
NRk,s,a	Characteristic tensile resistance of anchor	27.1 kN	42.4 kN	71.7 kN	ETA Table C1
γMs	Partial safety factor for steel	1.85	1.85	1.85	ETA Annex C1

Design Resistances

Channel	NRk,s,a (kN)	γMs	NRd,s,a (kN)
CPRO38	27.1	1.85	14.6
CPRO50	42.4	1.85	22.9
CPRO52	71.7	1.85	38.8

Worked Example

Given: CPRO50 channel, anchor tension Nᵃₑd = 13.90 kN Step 1: Look up characteristic resistance

NRk,s,a = 42.4 kN (from ETA Table C1)

Step 2: Apply partial safety factor

NRd,s,a = 42.4 / 1.85 = 22.92 kN

Step 3: Calculate utilisation

βN = 13.90 / 22.92 = 0.61 = 61%

Result: Verification PASSES (61% ≤ 100%)

Steel Failure — Channel Connection

This mode checks the connection between anchor and channel (the weld or mechanical connection).

Equation

NRd,s,c = NRk,s,c / γMs,ca

Parameters

Symbol	Description	CPRO38	CPRO50	CPRO52	Source
NRk,s,c	Characteristic resistance of connection	28 kN	32 kN	76 kN	ETA Table C1
γMs,ca	Partial safety factor	1.8	1.8	1.8	ETA Annex C1

Steel Failure — Channel Bolt

The T-bolt connecting the load to the channel must also be verified.

Equation

NRd,s,b = NRk,s,b / γMs2

Bolt Characteristic Resistances

Bolt Size	CPRO38	CPRO50	CPRO52	Source
M10	40.6 kN	—	—	ETA Table C7
M12	45.7 kN	59 kN	59 kN	ETA Table C7
M16	101.7 kN	109.9 kN	109.9 kN	ETA Table C7
M20	—	145.2 kN	145.2 kN	ETA Table C7

Partial safety factor: γMs2 = 1.87

Concrete Cone Failure

Equation

NRd,c = N⁰Rk,c × (Ac,N / A⁰c,N) × ψs,N × ψre,N × ψec,N / γMc

Basic Resistance

N⁰Rk,c = k × √fck × hef^1.5

Where:

Symbol	Description	Cracked	Uncracked	Source
k	Cracking factor	kcr,N	kucr,N	ETA Table C2

Cracking factors by channel:

Channel	kcr,N	kucr,N	hef (mm)
CPRO38	7.8	11.1	72
CPRO50	8.1	11.6	99
CPRO52	8.7	12.4	151

Area Ratio

The reference cone area assumes unlimited concrete:

A⁰c,N = scr,N × scr,N

Where scr,N = 3 × hef The actual area Ac,N is reduced by:

Proximity to edges
Overlap with adjacent anchors
Member thickness limitations

Reduction Factors

Edge distance factor:

ψs,N = 0.7 + 0.3 × (c / ccr,N) ≤ 1.0

Where ccr,N = 1.5 × hef Reinforcement factor:

ψre,N = 0.5 + hef/200 ≤ 1.0   (without supplementary reinforcement)
ψre,N = 1.0                    (with supplementary reinforcement)

Eccentricity factor:

ψec,N = 1 / (1 + 2eN/scr,N) ≤ 1.0

Partial factor: γMc = 1.5

Pullout Failure

Equation

NRd,p = NRk,p × ψc,p / γMp

Characteristic Resistances

Channel	Cracked NRk,p (kN)	Uncracked NRk,p (kN)	Source
CPRO38	13.6	19.0	ETA Table C2
CPRO50	18.4	25.8	ETA Table C2
CPRO52	32.2	45.1	ETA Table C2

Partial factor: γMp = 1.5

Pullout resistance is product-specific and determined by testing. Clariti uses certified ETA values directly.

Concrete Splitting

When It Applies

Splitting must be checked when:

Member thickness h < hmin (specified in ETA)
Edge distance c < ccr,sp
Spacing s < scr,sp

Minimum Member Thickness

Channel	hmin (mm)	Source
CPRO38	100	ETA Table B1
CPRO50	130	ETA Table B1
CPRO52	185	ETA Table B1

Equation

NRd,sp = N⁰Rk,c × (Ac,N/A⁰c,N)sp × ψs,N × ψre,N × ψec,N × ψh,sp / γMsp

Thickness factor:

ψh,sp = (h / hmin)^(2/3) ≤ 1.0

Partial factor: γMsp = 1.5

Safety Factors Summary

Failure Mode	Symbol	Value	Source
Anchor steel failure	γMs	1.85	ETA Annex C1
Anchor channel connection	γMs,ca	1.8	ETA Annex C1
Channel lips	γMs,l	1.8	ETA Annex C1
Tension bolt	γMs2	1.87	ETA Annex C1
Channel flexure	γMs,flex	1.15	ETA Annex C1
Pullout	γMp	1.5	ETA Annex C2
Splitting	γMsp	1.5	ETA Annex C2
Concrete cone/blowout	γMc	1.5	ETA Annex C2

Governing Failure Mode

Clariti determines the governing mode automatically:

ηsteel = NEd / NRd,s
ηcone  = NEd / NRd,c
ηpull  = NEd / NRd,p
ηsplit = NEd / NRd,sp

Governing mode = max(ηsteel, ηcone, ηpull, ηsplit)

The results panel highlights the governing mode and shows utilisation for all modes.

In Clariti

Clariti displays tension verification as:

Summary — Overall tension utilisation and governing mode
Breakdown — Each mode with its utilisation percentage
Expanded view — Full calculation with all intermediate values
ETA references — Source data for traceability

All factors and their values are shown with the equation that generated them, allowing full verification of the calculation.

Getting Started

How Calculations Work

EN 1992-4 Reference

User Guides

Overview

Verification Format

Steel Failure — Anchor in Tension

Equation

Parameters

Design Resistances

Worked Example

Steel Failure — Channel Connection

Equation

Parameters

Steel Failure — Channel Bolt

Equation

Bolt Characteristic Resistances

Concrete Cone Failure

Equation

Basic Resistance

Area Ratio

Reduction Factors

Pullout Failure

Equation

Characteristic Resistances

Concrete Splitting

When It Applies

Minimum Member Thickness

Equation

Safety Factors Summary

Governing Failure Mode

In Clariti

​Overview

​Verification Format

​Steel Failure — Anchor in Tension

​Equation

​Parameters

​Design Resistances

​Worked Example

​Steel Failure — Channel Connection

​Equation

​Parameters

​Steel Failure — Channel Bolt

​Equation

​Bolt Characteristic Resistances

​Concrete Cone Failure

​Equation

​Basic Resistance

​Area Ratio

​Reduction Factors

​Pullout Failure

​Equation

​Characteristic Resistances

​Concrete Splitting

​When It Applies

​Minimum Member Thickness

​Equation

​Safety Factors Summary

​Governing Failure Mode

​In Clariti

Overview

Verification Format

Steel Failure — Anchor in Tension

Equation

Parameters

Design Resistances

Worked Example

Steel Failure — Channel Connection

Equation

Parameters

Steel Failure — Channel Bolt

Equation

Bolt Characteristic Resistances

Concrete Cone Failure

Equation

Basic Resistance

Area Ratio

Reduction Factors

Pullout Failure

Equation

Characteristic Resistances

Concrete Splitting

When It Applies

Minimum Member Thickness

Equation

Safety Factors Summary

Governing Failure Mode

In Clariti