| 摘要 |
This section is of the type comprising two lateral flanges 2 joined by a web 3 and the said web 3 includes, on its outer face opposite the flanges 2, a reserve of material consisting of at least one rib 4 formed by bending the metal sheet and having, in cross-section, any shape whatsoever whose lateral walls, or sides 5 may be moved apart or brought together by changing the angles alpha which they form with the said web 3. <IMAGE>
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