1. Name

The title of this article uses a commonly-accepted expression, but it requires some comment.

"Lightweight structures": two words that are always difficult to define, and yet the term explicitly refers to the weight of the structures themselves.

• Isn't the word structures itself inappropriate? It is, if we're interested in a sequence in which the first thing we're talking about is a construction whose mode of assembly bears the name "structure".

  But civil engineering circles have long since disregarded the word "construction" whenever its function of resisting action is invoked. The word structure has supplanted it, but it has been qualified accordingly, according to the mood of the moment or the specific attentions of users: thus, if the material comes to the fore, we speak of concrete, wood...