These drawings and pictures illustrate various types of structural articles that are assembled from triangles, the strongest 2-dimensional shapes that can exist in the universe as we know it.

Typical bridge designs -
collections of triangles, for strength and stability
Typical bridge designs -
collections of triangles, for strength and stability
Typical roof support trusses -- again, collections of triangles, for strength and stability
Typical design of a construction crane -- again, a collection of triangles, for strength
and stability
Geodesic domes are among the most weight-efficient and strongest enclosing structures ever discovered. And, once again, they are made of triangles, for strength and stability