Concrete Column ACI 2011, Strength reduction factor for Column Interaction

during review design of concrete column, it's noticed that strength reduction factor considered as 0.65,

it's understood that strength reduction factor varies between 0.65 (compression control section) to 0.9 (tension control section),

by reviewing axial compression force, its value is relatively small (smaller than 0.1 fc' Ag), accordingly value of phi (strength reduction factor) is expected to be 0.9 not 0.65.

PDF