Neutral Axis

What is Neutral Axis?

The line in a bent section where longitudinal stress and strain are zero, separating tension from compression. For a symmetric elastic cross-section it sits at the centroid, but in reinforced concrete its position shifts once the section starts to crack.

The five clues

Engineerdle #49 described Neutral Axis with five clues, revealed one at a time from hardest to most direct. Each clue points at a different property of the concept.

1. 01A line where nothing much happens.
2. 02On one side of it fibres stretch; on the other they compress.
3. 03For a symmetric elastic section it passes through the centroid.
4. 04For reinforced concrete its position shifts as the section cracks.
5. 05It's where bending stress is zero.

More Structural Engineering concepts

• Slenderness RatioPuzzle #40
• Moment Distribution MethodPuzzle #35