TY JOUR TI STRUCTURAL SYNTHESIS OF THE FRAME KW rod system KW synthesis of structures KW variational principles KW equations of structure formation KW minimum volume of material JO Bulletin of Belgorod State Technological University named after. V. G. Shukhov AU Yuriev, A.G. AU Panchenko, L.A. PY 2026 IS 11 PB Belgorod State Technological University named after V.G. Shukhov