Shear Verification

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

Overview

Three shear failure modes must be checked:

Steel failure — Shear failure of anchor steel
Concrete edge failure — Breakout toward a free edge
Concrete pryout — Breakout on the back side of anchors

The governing mode depends on geometry, particularly edge distances and load direction.

Steel Failure in Shear

Equation

VRd,s = VRk,s / γMs

Where:
  VRk,s = k₂ × As × fuk

Symbol	Description	Source
k₂	Reduction factor for shear	0.6 (typical)
A_s	Stressed cross-section	ETA data
f_uk	Ultimate steel strength	ETA data
γ_Ms	Partial factor for steel	ETA (typically 1.0 for shear)

Notes

Shear steel resistance is typically lower than tension (k₂ = 0.6)
Lever arm effects may further reduce capacity
Product-specific values in ETA may differ

Lever Arm Effect

When shear acts with a lever arm (stand-off installation):

VRd,s = αM × VRk,s / γMs

Where:
  αM = lever arm reduction factor

For cast-in anchor channels, lever arm is typically zero (no stand-off).

Concrete Edge Failure

When It Governs

Edge failure typically governs when:

Shear acts toward a free edge
Edge distance is less than ~10 × h_ef
High shear loads relative to tension

Equation

VRd,c = V°Rk,c × (Ac,V / A°c,V) × ψs,V × ψh,V × ψec,V × ψα,V × ψre,V / γMc

Basic Resistance (V°_Rk,c)

V°Rk,c = k₁ × dnom^α × √(lf/dnom) × √fck × c₁^1.5

Where:
  k₁ = 1.7 (cracked) or 2.4 (uncracked)
  dnom = nominal anchor diameter
  lf = effective length under shear (≤ 8×dnom)
  c₁ = edge distance in load direction

Reference Area (A°_c,V)

A°c,V = 4.5 × c₁²

Actual area Ac,V reduced by:
  - Member thickness limitations
  - Spacing to adjacent anchors
  - Corner effects (two edges)

Reduction Factors

Edge distance factor (ψ_s,V):

ψs,V = 0.7 + 0.3 × c₂/(1.5×c₁) ≤ 1.0

Where c₂ is the perpendicular edge distance. Thickness factor (ψ_h,V):

ψh,V = (1.5×c₁/h)^0.5 ≤ 1.0

Applies when member thickness h < 1.5 × c₁. Eccentricity factor (ψ_ec,V):

ψec,V = 1/(1 + 2×eV/(3×c₁)) ≤ 1.0

Load direction factor (ψ_α,V):

ψα,V = √(1/(cos²αV + (sin²αV)/2.5)) ≤ 1.0

Where α_V is the angle between load and edge. Reinforcement factor (ψ_re,V):

ψre,V = 1.0   (with edge reinforcement)
ψre,V = 0.7   (without edge reinforcement, narrow member)

Example Calculation

Given:

c₁ = 150 mm (edge distance in load direction)
c₂ = 200 mm (perpendicular edge)
h = 300 mm (member thickness)
f_ck = 30 MPa
d_nom = 10 mm, l_f = 80 mm
Cracked concrete

Calculate:

Reference area:
  A°c,V = 4.5 × 150² = 101,250 mm²
  Ac,V = Limited by geometry... (assume no reduction)
  Ratio = 1.0

Edge factor (c₂ direction):
  c₂/(1.5×c₁) = 200/(1.5×150) = 0.89
  ψs,V = 0.7 + 0.3 × 0.89 = 0.97

Thickness factor:
  1.5×c₁ = 225 mm < h = 300 mm
  ψh,V = 1.0 (no reduction)

Basic resistance:
  V°Rk,c = 1.7 × 10^0.5 × √(80/10) × √30 × 150^1.5
  V°Rk,c = 1.7 × 3.16 × 2.83 × 5.48 × 1837
  V°Rk,c = 153 kN

Design resistance:
  VRd,c = 153 × 1.0 × 0.97 × 1.0 × 1.0 × 1.0 × 1.0 / 1.5
  VRd,c = 99 kN

Edge failure is often the governing mode for shear toward edges. Always check edge distances carefully and consider if reinforcement can be added.

Concrete Pryout Failure

When It Applies

Pryout governs for:

Short, stiff anchors (h_ef < 60mm typically)
Shear away from edges
High concrete strength (concrete cone capacity is high)

Equation

VRd,cp = k × NRd,c

Where:
  k = pryout factor
    = 1.0 for hef < 60mm
    = 2.0 for hef ≥ 60mm
  NRd,c = concrete cone resistance (tension)

Logic

Pryout is related to concrete cone because the failure mechanism involves a concrete breakout on the opposite side from the shear load. The pryout factor k accounts for the different loading geometry.

Example

Given:

h_ef = 50 mm
N_Rd,c = 20 kN (from tension calculation)

Calculate:

k = 1.0 (since hef = 50 < 60mm)
VRd,cp = 1.0 × 20 = 20 kN

For deeper embedment (h_ef = 80 mm):

k = 2.0
VRd,cp = 2.0 × 20 = 40 kN

Pryout resistance doubles when embedment exceeds 60mm. This is a significant threshold for anchor channel selection.

Shear Load Direction

The governing failure mode depends heavily on load direction:

Direction	Likely Governing Mode
Toward near edge	Concrete edge failure
Away from edges	Pryout or steel
Parallel to edge	Steel (often), or edge if close
Oblique	Check all modes

Clariti automatically evaluates all modes for any load direction and reports the governing one.

Governing Failure Mode

Utilization for each mode:
  ηsteel   = VEd / VRd,s
  ηedge    = VEd / VRd,c
  ηpryout  = VEd / VRd,cp

Governing mode = max(ηsteel, ηedge, ηpryout)

In Clariti

Shear verification displays:

Load direction — Visual indicator of shear relative to edges
Edge distances — All edge distances with critical values
Mode breakdown — Each mode with utilization
Governing indicator — Highlighted governing mode
Expanded calculations — Full EN 1992-4 equations with values

The 3D view shows the shear vector and proximity to edges, helping you understand why certain modes govern.

Getting Started

How Calculations Work

EN 1992-4 Reference

User Guides

Overview

Steel Failure in Shear

Equation

Notes

Lever Arm Effect

Concrete Edge Failure

When It Governs

Equation

Basic Resistance (V°_Rk,c)

Reference Area (A°_c,V)

Reduction Factors

Example Calculation

Concrete Pryout Failure

When It Applies

Equation

Logic

Example

Shear Load Direction

Governing Failure Mode

In Clariti

​Overview

​Steel Failure in Shear

​Equation

​Notes

​Lever Arm Effect

​Concrete Edge Failure

​When It Governs

​Equation

​Basic Resistance (V°Rk,c)

​Reference Area (A°c,V)

​Reduction Factors

​Example Calculation

​Concrete Pryout Failure

​When It Applies

​Equation

​Logic

​Example

​Shear Load Direction

​Governing Failure Mode

​In Clariti

Overview

Steel Failure in Shear

Equation

Notes

Lever Arm Effect

Concrete Edge Failure

When It Governs

Equation

Basic Resistance (V°_Rk,c)

Reference Area (A°_c,V)

Reduction Factors

Example Calculation

Concrete Pryout Failure

When It Applies

Equation

Logic

Example

Shear Load Direction

Governing Failure Mode

In Clariti