For some of the shear design parameters, additional user defined limits can be applied - where this is the case minimum and maximum values are specified in Design Settings > Concrete > Cast-in-place > Column > Reinforcement Layout. These are considered in addition to the EC2 or NA recommendations.

Minimum Shear Link Diameter

φ_w,min = MAX[ 6mm, 0.25 * largest longitudinal bar diameter ]

Maximum Span Region Shear Link Spacing

• For design to UK NA, Irish NA, Malaysian NA and Singapore NA: ¹

  φ_w,max = MIN[ 20 * smallest longitudinal bar diameter, lesser column dimension, 400mm ]

  Note:

  For UK NA when concrete class > C50/60 there are separate calculations in clause 9.5.3(3). These are not implemented but a warning is displayed in this situation.

• For design to EC2 Recommendations:, Swedish NA

  φ_w,max = MIN[ 20 * smallest longitudinal bar diameter, lesser column dimension, 400mm ]

• For design to Finnish NA and Norwegian NA:

  φ_w,max = MIN[ 15 * smallest longitudinal bar diameter, lesser column dimension, 400mm ]

  Note that in the Norwegian NAthis limit is reduced by a factor of 0.6 for strength classes equal or above C55/67.

Support Region Shear Link Spacing

For support regions, the maximum link spacing is reduced by 40%. ²

Long Term Compressive Strength Factor for Shear

• For design to EC2 Recommendations, UK NA, Irish NA, Malaysian NA, Singapore NA and Swedish NA: ³

  α_ccw = 1.0

• For design to Finnish NA and Norwegian NA:

  α_ccw = 0.85

Design Concrete Compressive Strength for Shear

Cracked Concrete Reduction Factor, v

• For design to EC2 Recommendations, UK NA, Irish NA, Malaysian NA, Singapore NA, Finnish NA, Norwegian NA and Swedish NA: ⁶

  v = 0.6 * (1 - (f_ck / 250))

Cracked Concrete Reduction Factor, v₁

• For design to UK NA: ⁷

  v₁ = v* (1 - (0.5 * cos(α))

  α is the inclination of links.

  Note that links in columns are always assumed to be at 90° to column direction.

  Therefore v₁ = v

• For design to EC2 Recommendations, Irish NA, Malaysian NA, Singapore NA, Finnish NA, Norwegian NA and Swedish NA:

  v₁ = v

Minimum Shear Reinforcement Ratio

• For design to EC2 Recommendations, UK NA, Irish NA, Malaysian NA, Singapore NA, Finnish NA, and Swedish NA:: ⁸

  ρ_w,min = 0.08 * √(f_ck) / f_yk

• For design to Norwegian NA:

  ρ_w,min = 0.1 * √(f_ck) / f_yk

Maximum Angle of Compression Strut

• For design to EC2 Recommendations, UK NA, Irish NA, Malaysian NA, Singapore NA, Finnish NA, Norwegian NA and Swedish NA: ⁹

  cot(θ_max) = 1

  θ_max = 45°

Minimum Angle of Compression Strut

• For design to EC2 Recommendations, UK NA, Irish NA, Malaysian NA and Singapore NA:¹⁰

  cot(θ_min) = 2.5

  θ_min = 21.8°

• For design to Norwegian NA:

  If σ_t = N_Ed/A_c < f_{ctk, 0,05}

  cot(θ_min) = 2.5

  θ_min = 21.8°

  else

  cot(θ_min) = 1.25

  θ_min = 38.7°

Angle of Compression Strut

• For design to UK NA: ¹¹

  If N_Ed ≥ 0 i.e. compression

  θ = 0.5 * arcsin(2 * v_Ed / (0.9 * α_cw * v₁ * f_cwd))

  else

  cot(θ) = 1.25

  θ = 38.7°

• For design to EC2 Recommendations, Finnish NA, Norwegian NA and Swedish NA:

  θ = 0.5 * arcsin(2 * v_Ed / (0.9 * α_cw * v₁ * f_cwd))

• For design to Irish NA, Malaysian NA and Singapore NA:

  If NEd ≥ 0 i.e. compression

  θ = 0.5 * arcsin(2 * v_Ed / (0.9 * α_cw * v₁ * f_cwd))

  else

  cot(θ) = 1.00

  θ = 45°

Stress State Factor

• For design to EC2 Recommendations, UK NA, Irish NA, Malaysian NA, Singapore NA, Finnish NA, Norwegian NA and Swedish NA:

  If σ_cp ≤ 0

  α_cw = 1.0

  else if 0 < σ_cp ≤ 0.25 * f_cd

  α_cw = 1.0 + (σ_cp / f_cd)

  else if 0.25 * f_cd < σ_cp ≤ 0.5 * f_cd

  α_cw = 1.25

  else if 0.5 * f_cd < σ_cp ≤ f_cd

  α_cw = 2.5 * (1.0 - (σ_cp / f_cd))

Minimum Shear Strength

• For design to EC2 Recommendations, UK NA, Irish NA, Malaysian NA, Singapore NA, Finnish NA and Swedish NA: ¹²

  v_min = 0.035 * k^1.5 * f_ck ^0.5

• For design to Norwegian NA:

  v_min = 0.035 * k^2/3 * min(f_ck, 0.65)^0.5

Footnotes