Which bending scenario indicates a negative moment?

A bending scenario indicates a negative moment when the beam or structural element is concave down. In this position, the top fibers of the beam are in compression while the bottom fibers are in tension. This configuration typically occurs in structures where the loads applied exceed the beam's ability to resist without undergoing a downward curvature, signaling that negative bending moments are at play.

In structural analysis, negative moments are usually present at supports or points of inflection in beams, leading to a downward curvature. Understanding this behavior is crucial as it affects how the structure will respond to loads and is essential in the design to ensure structural integrity.

Concave up, on the other hand, indicates a positive moment condition, where the beam bows upward, resulting in tension on the top fibers and compression on the bottom. Linear bending refers to uniform bending behavior, and twisted bending involves torsion rather than moment, which does not directly relate to the identification of negative moments.