Where is a beam's weakest point?

Where is a beam's weakest point?

You walk across a bridge, and it holds your weight without a second thought. But inside the steel, a fierce, invisible struggle is happening. Let's look at a classic simply supported beam.

Back in 1750, Euler and Bernoulli realized a beam doesn't just sit there—it actively fights back. It resists being sliced in half by shear forces, and it resists bending into a U-shape through internal moments.

Back in 1750, Leonhard Euler and Daniel Bernoulli discovered a hidden mathematical language inside solid beams. They realized that bending and shearing aren't just random forces—they actively drive each other.