Question

Which of the following relation is correct for plastic section modulus, Zo ?

(a) Zp = 2A(y1+y2)

(b) Zp = A(y1+y2)/2

(c) Zp = A(y1+y2)/4

(d) Zp = 4A(y1+y2)

I had been asked this question in final exam.

The question is from Plastic Theory topic in division Plastic and Local Buckling Behaviour of Steel of Design of Steel Structures

Answer 1

The correct option is (b) Zp = A(y1+y2)/2

Easy explanation: Zp = A(y1+y2)/2, where A= area of cross section, y1 and y2 are centroids of portion above and below neutral axis respectively. Plastic modulus is defined as combined statical moment of cross sectional area above and below the equal-area axis.