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D1.F.5.1 Strength Design

All column designs will be based on a uniform distribution of reinforcement around the column perimeter. The design options to control a column design will be based on the CRDO parameter setting.

Column resistance is calculated based on strain compatibility and interaction surface calculations.

The following conditions should be checked (
  • ϕPn ≥Pu
  • ϕMn ≥ Mu
  • ϕVn ≥ Vu
  • ϕTn ≥ Tu

ϕPn ≥ Pu

ϕMn ≥ Mu

ϕVn ≥ Vu

ϕ Tn ≥ Tu

Where the nominal axial compressive strength, Pn , shall not exceed Pn,max in accordance with Table 22.4.2.:
  • Pn,max = 0.80 Po for ties
  • Pn,max = 0.85 Po for spirals
  • Po = 0.85 f´c (Ag -Ast) + fyAst)
the total area (of nonprestressed) longitudinal reinforcement
the gross area of the concrete section
the specified compressive strength of concrete
the specified yield strength of passive reinforcement
the nominal flexural strength
the nominal shear strength
the nominal torsional moment

The design is performed in two steps considering the longitudinal reinforcement design for axial-bending in an initial step, and the shear and torsion design including the longitudinal reinforcement for torsion tension in a latter pass together with the transverse design.

The minimum area of longitudinal reinforcement is taken as 0.01Ag and the maximum as 0.08Ag. In agreement with the commentary a warning is triggered when the reinforcement ratio is over 4 percent due to possible lap splices zones.