Question

If order of indeterminacy is r, then minimum number of plastic hinges required for total collapse is _______

(a) r-1

(b) r

(c) r+1

(d) r+2

The question was asked in an international level competition.

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

Answer 1

Correct option is (c) r+1

For explanation I would say: If order of indeterminacy is r, then minimum number of plastic hinges required for total collapse is r+1.