[T]here are three different but interconnected conceptions to be considered in every structure, and in every structural element involved: equilibrium… - Eduardo Torroja

[E]very structure has a resistant function to fulfill... to ensure ...the static equilibrium of the structure for a long period of time.

Stress phenomena are... not independent of scale, as was the case pertaining to simple external static equilibrium. ...with increasing dimensions of a structural element the volume and therefore the proper weight increases more rapidly than its cross-sectional areas...

The variety of exterior forms in concrete is limited only by the cost of forming; and its thickness is limited only by the size of aggregates, gravel, and sand.