Why Are Triangles Used in Trusses?

Rigidity

• A triangle has three sides and three angles, and each angle is held solidly in place by the side opposite it. This means that a triangle's angles are fixed, and that if pressure is placed anywhere on a triangle, its angles, unlike those of other shapes, will not change.

Forces

• When a force is applied to a triangle, the resulting pressure is directed sideways rather than down. This means that sides of the triangle are in either compression or tension, and that there is thus no bending movement.

Openness

• Since the center of a triangle does not contribute to its geometric rigidity or structural integrity, the center of a triangle can remain open. As one of the goals in erecting a truss is minimizing its weight, triangles are an appropriate shape to use.