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 (10.5.1.1)

ϕPn ≥Pu
ϕMn ≥ Mu
ϕVn ≥ Vu
ϕTn ≥ Tu

ϕP_n ≥ P_u

ϕM_n ≥ M_u

ϕV_n ≥ V_u

ϕ T_n ≥ T_u

Where the nominal axial compressive strength, P_n , shall not exceed P_n,max in accordance with Table 22.4.2.:

P_n,max = 0.80 P_o for ties
P_n,max = 0.85 P_o for spirals
P_o = 0.85 f´_c (A_g -A_st) + f_yA_st)

where

A_st	=	the total area (of nonprestressed) longitudinal reinforcement
Ag	=	the gross area of the concrete section
f´_c	=	the specified compressive strength of concrete
f_y	=	the specified yield strength of passive reinforcement
M_n	=	the nominal flexural strength
V_n	=	the nominal shear strength
T_n	=	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.