Name of the point where the bending moment changes sign In a continuous bending-moment diagram, the point at which the bending moment passes through zero and changes sign is called the:

Introduction / Context:
Terminology matters when interpreting diagrams. The location where bending moment switches from sagging to hogging (or vice versa) has a specific name, often used in detailing and analysis notes.

Given Data / Assumptions:

• Beam or frame with regions of positive and negative bending.
• Continuous bending-moment diagram with at least one internal zero crossing.

Concept / Approach:
The point where the bending moment M changes sign is called the point of contraflexure (also written as counterflexure). At this point, curvature changes sign as well, although the point of inflexion is a broader mathematical term where curvature changes sign in a deflection curve; in beam theory, the two are related but the standard term tied to M = 0 sign change is contraflexure.

Step-by-Step Solution:

Verification / Alternative check:
Check the corresponding shear diagram; a zero in M does not necessarily require zero shear.

Why Other Options Are Wrong:

• Point of inflexion (option a) describes curvature change in the deflected shape; terminology in beam BMD context prefers contraflexure.
• Point of virtual hinge (option c) refers to a plastic hinge or a released moment location, not merely a sign change of M.
• All of the above (option d) mixes distinct concepts.

Common Pitfalls:
Confusing zero bending moment at supports of simple spans with internal points of contraflexure.

Final Answer:
Point of contraflexure