1. Forging new generations of engineers
Strength of Shapes
Principles of EngineeringTM
Lesson Statics
Forging new generations of engineers
Project Lead The Way, Inc.
Copyright 2007

2. Strength of Shapes

3. Forces in Tension and Compression
A force is a push or pull exerted by one object on another.
A tensile force expands or lengthens the object it is acting on.
A compressive force compresses or shortens the object it is acting on.

4. Forces in Tension and Compression The rope is in tension
The stand is in compression.

5. Forces on Shapes Which shapes are strongest?
Which deform when in tension?
Which deform in compression?
It depends on where you hold it and where you push or pull (top, bottom, sides…). Insert pipe cleaners into plastic straws and twist the ends to test different shapes. What happens?

6. Forces on Shapes
Engineers consider shapes under heavy loads when building large structures.
Triangles are the only shapes that cannot be deformed without changing the length of one of its sides
Arches are strong because the force resulting from a heavy load placed at the top spreads down the sides to the foundation.
A group of arches placed around a central point creates a dome, which distributes loads down through curving sides to the foundation.

7. Triangles Bank of China Tower Eiffel Tower Stansted Airport
Centre Pompidou

8. Iron Bridge at Coalbrookdale
Arches
San Lorenzo, Florence
Musee d'Orsay
Roman Colosseum
Iron Bridge at Coalbrookdale

9. Pantheon, Paris - Interior
Domes
Florence Cathedral
Pantheon, Paris - Interior

10. Applications Psyclone Rollercoaster- triangles in structure
US Pavilion at Expo '67 - spherical structure made of triangles
Dome tent -poles bent into arches with nylon fabric in tension.
Campo Volantin Footbridge - arch with cables in tension