Modeling dynamic problems of thin-walled framework
The article describes the flexural and torsional vibrations of an open profile thin -walled rod with one cross section 
 symmetry axis. When solving the rod vibrations problem the static task is considered with the addition of inertia forces, i.e. using the 
 principle of Dalembert. The weight and stiffness of the rod are accepted as constant. Based on energy relatios the mass matrices are 
 obtained in the explicit form of thin-walled rod finite elements that are in bending and torsion, and also a spatial finite element. The 
 article shows comparative calculations on free and forced vibrations of П-shaped frame that is formed of rolled channel and double 
 tee. The frame model uses beam finite and thin -walled rod elements, i.e., the flexural form of vibrations without considering torsion-al inertia of the rods and the torsional vibrations form respectively. There are values of the lower frequencies and corresponding 
 modes from frames plane in the beam-column joint with free vibrations, as well as the maximum normal stresses in the profilecross -sections. The method of modeling is implemented in applications computer programs.