Strengthening Structures
How structures stand up and how to make them stronger, stiffer and more stable: wide bases, triangles, tubes, folds and cross-bracing; why some shapes resist pushing and pulling, and how real bridges and towers use these tricks
What a learner can do afterwards
- Explain why a triangle or a folded sheet is stiffer than a flat one (e.g. corrugated card vs plain card)
- Suggest ways to stop a model tower falling over (e.g. widening the base, adding diagonal braces)
- Point out strengthening features in real structures (e.g. triangles in a bridge truss or a crane)
The lesson
A tower or bridge has to hold its own weight without falling over or bending. Whether it stays up often depends on its shape, not just what it's made from. The right shape spreads out pushes and pulls so nothing gives way.
Zara built a tower from spaghetti and marshmallows, but it wobbled and leaned. First she widened the base, spreading the legs further apart. Then she added diagonal spaghetti braces between the legs, turning each gap into a triangle. The tower stopped wobbling and stood tall.
A flat sheet of card bends easily, but fold it into ridges and it barely bends at all. That's why cardboard boxes use ridged card inside. Rolling a flat sheet into a tube does the same trick: it makes thin material much stiffer without using any extra material.
Look closely at a big crane or a bridge made of steel beams and you'll spot triangles everywhere in the frame. Engineers use triangles on purpose, because a triangle can carry heavy pushes and pulls without changing shape. That's the same trick as the braces in Zara's tower, just built from steel instead of spaghetti.
Wide bases, triangles, folds and tubes all help a structure carry pushes and pulls without falling over or bending.
Watch it
Where it sits
Learn first
This opens up
Nothing builds on it yet.
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.