How can a shape be strong?
In: Engineering
The shape is rigid because in order to deform you need to stretch and compress the members. The shape is strong because essentially the loads to be carried almost entirely by compression and tension forces.
This is in contrast to any shape with more sides. If you take a square frame, fix the base, and try to push it over – there are tension and compression forces, but the members that make it up are also trying to bend.
The way the section properties work any given shape has much less capacity to resist bending than it does to resist tension/compression, and the stiffness against bending is significantly less than the stiffness against stretching/compressing.
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