Strength of Shape

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Forging new generations of engineers
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Strength of Shapes
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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.
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Forces in Tension and Compression
The rope is in tension
The stand is in compression.
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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?
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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.
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Triangles
Bank of China Tower
Eiffel Tower
Stansted Airport
Centre Pompidou
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Arches
Musee d'Orsay
San Lorenzo, Florence
Roman Colosseum
Iron Bridge at Coalbrookdale
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Domes
Florence Cathedral
Pantheon, Paris - Interior
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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