Minimal mandrel diameter - 5.2.4.1

The mandrel diameter should not exceed minimal value defined in 5.2.4.1. Check looks as follows. Calculation of minimal defined mandrel diameter of stirrups:

ϕ_m,min = Coeff_ϕm ∙ φs

 

where

• Coeff_ϕm  - value defined in Stirrup layer - Diameter of mandrel

• φ_s - diameter of defined stirrup

 

Furthermore minimal allowed mandrel diameter of stirrup is determined as follows

for φs ≤ 16 mm; φm,min = 4 ∙ φs

 

Finally unity check is calculated as follows:

UC5.2.4.1 = φm,min / φm