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… - Eduardo Torroja

The equilibrium... in order to become static—should be steady, permanent, lasting. ...This type of equilibrium... is... independent of any scale. A reduced model will show the same effects as the proper structure. Experiments on models are simple and... instrumental for understanding such structural problems.

[M]aterials should resist mechanical forces and other effects... starting with all types of loading and external forces... and with the mechanical properties of the materials... constitutes the part given most emphasis in technical books and schools.

Long before... our techniques of today, men could conceive and build structures adapted to the requirements of resistance... because he had observed... the branches of a tree bending under the weight of fruits and the tensioned cords of strings in which children have rocked from time immemorial...