Question

Which of the following condition is true for uniqueness theorem?

(a) load must be greater than collapse load

(b) load must be less than collapse load

(c) load must be equal to collapse load

(d) load cannot be related to collapse load

I had been asked this question in an interview for internship.

My question is from Theorem of Plastic Collapse & Methods of Plastic Analysis topic in chapter Plastic and Local Buckling Behaviour of Steel of Design of Steel Structures

Answer 1

The correct option is (c) load must be equal to collapse load

For explanation: For given frame and loading, if at least one safe and statically admissible bending moment distribution can be found, and if in this distribution  bending moment is equal to fully plastic moment at sufficient cross sections to cause failure of frame as a mechanism due to rotation of plastic hinges, then corresponding load will be equal to collapse load.