Explanations about the rules DTU:
This is a reference to the various DTU "Document Technique Unifié"
( Unified Technical Document) for supporting materials
T he text "recommendations" refers to regulations concerning structures made of steel, aluminium and wood :

CM means "Constructions Métalliques" (Metal Construction)
(19) 66 is the year of publication.

AL stands for "Aluminium", published in 1976,

and CB 71 means "Constructions Bois" (Wood Constructions), published in 1971;
CM66: Steel Constructions :
The sections 1.21 and 1.23 cover the methods of justification on the principle of weighting load coefficients.
Paragraph 1.21 gives the value of the weighting factors for the following cases:

work under SLS, taking into account the permanent loads, variable loads and effects of temperature (1.211),

erection (1.212)

and exceptional circumstances (1.213).
Section 1.23 describes the verification methods.
AL76 : Aluminum :
There are similar texts for aluminum to those for steel constructions.
Paragraph 3.32 gives the values of the weighing factors, and paragraph
3.34 provides the methods of verification.
CB 71: Wood :
For wood, in the same spirit, 1.21 corresponds to the expressions of the total weighted stresses involved in the calculations, and 1.22 to the verification in the cases of permanent loads, operating loads and climate loads.
The latest version of the Recommendations has been released in 2007.
Since then, Eurocodes have gradually replaced those documents. These texts are completely replaced today in France by the corresponding
Eurocodes:
EN 1993 (Steel)
EN 1999 (Aluminium) and EN 1995 (Wood)