Question

Which of the following expression for reduced plastic moment capacity is correct?

(a) Mfr = 0.25bftf^2fyf {1-[Nf/( bftffyf/γm0)^2]}

(b) Mfr = bftffyf {1-[Nf/( bftffyf/γm0)]}

(c) Mfr = 0.25bftf {1+[Nf/( bftffyf/γm0)]}

(d) Mfr = 0.25bf {1+[Nf( bftffyfγm0)^2]}

This question was addressed to me during an interview.

This interesting question is from Web Panel Subjected to Shear in chapter Gantry Girders, Design of Plate Girders & Industrial Buildings of Design of Steel Structures

Answer 1

The correct option is (a) Mfr = 0.25bftf^2fyf {1-[Nf/( bftffyf/γm0)^2]}

The best explanation: The reduced plastic moment capacity of respective flange plate is calculated after accounting for axial force in flange, due to overall bending and any external axial force in the cross section. It is given by Mfr = 0.25bftf^2fyf {1-[Nf/( bftffyf/γm0)^2]}, where bf and tf are width and thickness of flange respectively, fyf is yield stress of flange and Nf is the axial force in flange.