10 or 10 gp are disposed perpendicularly to the retaining flanges 110 it will be noted that the bridge diaphragm 50 39 of fig6 is more elongate than the diaphragm 50 of fig5 and that it has flange members designated here by numeral 42 whereby the entire bridge is approximately omega shaped in cross section a perforation 55 spaced from the arris 63 and 62 permits the introduction of a lever for compressing the web 134 of the elementary profile 33 by forming a loop illustrated in fig8 the diaphragm 50 tending to form its fold along a line joining the perforations 56 and 57 finally as shown in fig5 a square perforation 65 is formed astride in one of the wall webs 134 and permitting if necessary the retaining flange 136 to be deformed relative to flange 110 to constitute a complementary fixing without adversely affecting the rigidity of this flange which is firmly held by this bridge the compressive diaphragms of the illustrated bridges illustrate a notable advance which makes them into a connecting means each portion of which constitutes a retaining and blocking means each compressive diaphragm being applicable to any of the constituent elements of the composite structures in order to co operate in the stiffening an interconnection of the subassemblies and assemblies partly at two sides by a first perpendicular flange 104 itself extended perpendicularly towards the central portion of.