Question

Which of the following assumptions is not correct for plastic design?

(a) plastic hinge rotations are small compared with elastic deformations so all the rotations are concentrated at plastic hinges

(b) segments between plastic hinges are rigid

(c) influence of normal and shear forces on plastic moments is not considered

(d) plane section remains plane after bending and the effect of shear is neglected

This question was addressed to me during an online interview.

My question comes from General Requirements for Plastic Design and Plastic Hinge in division Plastic and Local Buckling Behaviour of Steel of Design of Steel Structures

Answer 1

Right answer is (a) plastic hinge rotations are small compared with elastic deformations so all the rotations are concentrated at plastic hinges

To elaborate: The plastic hinge rotations are large compared with elastic deformations so all the rotations are concentrated at plastic hinges. The segments between plastic hinges are rigid. The influence of normal and shear forces on plastic moments is not considered. The plane section remains plane even after bending and the effect of shear is neglected.