The process of optimizing the applied sections in steel frames with elements of variable stiffness, formed from rolled I-beams by their diagonal dissolution and subsequent welding, is considered. A table with groups of I-beams according to GOST R 57837-2017 is proposed, which are advisable to be used together to form a monosymmetrical I-beam of variable height. An algorithm for finding the optimal section is proposed, taking into account the discreteness of the assortment. The calculation of a typical building structure code 828KM according to the proposed algorithm is carried out and a comparative analysis of the applied sections with the found optimized sections is presented. The possibility of obtaining a more economical supporting structure, both in terms of metal consumption and in terms of the cost of rolled products, is noted.

Keywords: variable section, variable stiffness, diagonal opening, I-beam, steel frame