To the calculation of steel structures from thin-walled rods

The article contains a brief historical essay on the main ideas for calculating systems composed of thin-walled rods of open profile. The main approaches to the calculation of these systems taking into account the inequality of nodal deplanations are analyzed. It is proposed to use the finite element method using thin finite rods and specially constructed superelements as finite elements, which take into account the participation of nodal joints. The stiffness matrix of a thin-walled rod of the 14th order, built on the basis of the classical Vlasov's non-slip theory for open-profile rods, when the cross-sectional displacement is taken into account. Nodal superelements consist of shell finite elements and have m deplanation degrees of freedom according to the number of rods that approach the node. With the help of the matrix of stiffness of the nodal superelement, the connection between the deplanai, which affect the node, and the reactive forces, which have the form of bimoments realized. The method of construction of the node stiffness matrix is ​​indicated, which is based on the use of infinitely rigid bodies, displacements and rotations of which allow to simulate the influence of deplanations on the node. The peculiarities of the assembly operation in the presence of nodal superelements are indicated. Possible variants of inclusion of the considered technique in software complexes for calculation of building designs are specified.