"Reverse" method of calculating steel structure rod elements reinforced under load by increasing cross sections
To develop practical recommendations for strength and stability analysis in the general case of steel structure rod elements reinforced under load, there is proposed a «reverse» numerical-analytical calculation method, which allows reducing the calculation time by several orders of magnitude if compared with the currently used methods. For a given «elastic» limit state in the cross section corresponding to the criterion of maximum plastic deformation numerically, using the «Section» algorithm , the real limiting state of strength is established, namely, the general loading parameter and its relative eccentricities и . The results obtained in this way are more reliable than those according to SP 16.13330.2017, since the development of plastic deformations is determined by the joint action of forces. The stability of rod elements beyond the elastic limit is known to be characterized by a violation of the equilibrium deformed state. Therefore, following the technique of solving strength problems at a number of ultimate deformations by the «reverse» analytical method for the given flexibilities of the rod compressed with equal end uniaxial or biaxial eccentricities, the corresponding parameters of the total loading and its non-deformational eccentricities и are determined. In this case, the buckling factor will correspond to at and . Analytical solutions of such problems have sufficient accuracy for design practice and provide for all possible forms of buckling, namely, lateral, lateral-torsional and spatial ones.