The article presents an analysis of methods for strengthening reinforced concrete columns without changing the original design scheme. The calculation of reinforcement with a metal collar, a reinforced concrete collar, using prestressed struts and reinforcement with composite materials under central and eccentric compression is performed. A comparative analysis of the technical indicators of the considered reinforcement methods is made. A strategy for selecting a method for strengthening reinforced concrete columns is formed. An analysis of the optimal areas of application of various methods for strengthening reinforced concrete columns shows that the choice of a specific technology should be determined by the nature of their stress state depending on the magnitude of the eccentricity of load application. This study confirms that there is no universal "best" method for strengthening reinforced concrete columns; each of the considered methods has its own advantages and disadvantages. The results allow choosing optimal solutions based on the criteria of efficiency, reliability and cost-effectiveness.

Keywords: columns, reinforced concrete, steel, reinforcement, frame, carbon fiber, comparison, optimal method

The article presents the calculation of reinforced concrete column reinforcement using a metal cage made of angles, taking into account the physical nonlinearity of materials within the framework of the Lira CAD software package. The use of a nonlinear approach is due to the inability of linear methods to adequately reflect the real behavior of concrete and steel under load, in particular, their destruction and gradual loss of rigidity. This paper presents a model that takes into account the nonlinear stiffness characteristics of concrete and steel in accordance with regulatory documents. Taking into account the physical nonlinearity of materials when calculating column reinforcement is critically important for reliable modeling of the structure's behavior and preventing underestimation of the risks of destruction. It is necessary to check the structure for local destruction at each stage of loading to ensure the reliability of calculations and the safety of the structure. The use of specialized software with the ability to stage-by-stage loading and checking for local destruction allows you to obtain accurate results and justify optimal design solutions.

Keywords: columns, reinforced concrete, steel, strengthening, jacket, calculation, physical nonlinearity, software package, stresses, strains