Question

Which of the following relation is correct for rectangular section of width b and depth d subjected to axial force N together with moment M?

(a) (Mpr/Mp) + (N/Np)^2 = 1

(b) (Mpr/Mp) – (N/Np)^2 = 1

(c) (Mpr/Mp) + (N/Np) = 1

(d) (Mpr/Mp) – (N/Np) = 1

The question was asked in homework.

Origin of the question is Plastic Design of Portal Frames, Effect of Axial and Shear force on Plastic Moment Capacity topic in chapter Plastic and Local Buckling Behaviour of Steel of Design of Steel Structures

Answer 1

Correct option is (a) (Mpr/Mp) + (N/Np)^2 = 1

To explain: For a rectangular section of width b and depth d subjected to axial force N together with moment M, (Mpr/Mp) + (N/Np)2 = 1, where Mpr is moment with axial force, Mp is moment with axial force, Np is axial force without any moment.