Theory of Structures
For calculating the allowable stress of long columns σ0 = σy/n [1 - a (1/r)²]is the empirical formula, known as

Straight line formula
Perry
Parabolic formula
Rankine

ANSWER DOWNLOAD EXAMIANS APP

Theory of Structures
Slenderness ratio of a long column, is

Radius of gyration divided by area of cross-section
Area of cross-section divided by least radius of gyration
Area of cross-section divided by radius of gyration
Length of column divided by least radius of gyration

ANSWER DOWNLOAD EXAMIANS APP