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Beam Bending Explained (Using the Cartoon)

This cartoon shows how a beam behaves when a load is applied.

1️⃣ Load Applied on Top

The red arrow labelled LOAD shows a downward force acting on the beam.
This force causes the beam to bend.

2️⃣ Neutral Axis

The middle horizontal line is the neutral axis.

At this line → No tension or compression

It separates the compression zone (top) from the tension zone (bottom).

3️⃣ Top Part = Compression Zone

The person on top of the beam represents compression.

When load pushes down, the top fibers get shorter.

This is why in RCC beams, concrete handles the compression at the top effectively.

4️⃣ Bottom Part = Tension Zone

The person pulling downward at the bottom shows tension.

The bottom of the beam stretches.

Concrete is weak in tension, so steel reinforcement is required at the bottom.

This is why the main reinforcement bars are placed at the bottom of simply supported RCC beams.

5️⃣ Reinforcement

The black bars on the sides represent steel reinforcement.
Steel handles tension because:
✔ Steel is strong in tension
✔ Steel and concrete bond very well
✔ They expand equally with temperature (same thermal expansion)

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