The object of research is methods for determining reliability indicators, as well as methods for analyzing the propensity to develop progressive destruction in steel rod structures of increased responsibility that are many times statically indeterminate. The current state of the regulatory framework in the field of ensuring the reliability of building constructions is analyzed. The current regulatory framework in the field of preventing the development of progressive collapse of constructions is analyzed. Ambiguities in determining reliability indicators in difficult spatial constructions are noted. The question of a reasonable choice of a construction element, the destruction of which can cause the process of progressive collapse, is considered. The authors note the need to develop a clear methodology for determining the reliability characteristics of spatial many times statically indeterminate rod constructions of increased responsibility. Method. Based on the finite element method in a geometrically and structurally nonlinear formulation, an algorithm for determining the totality of key construction elements has been developed. The main purpose of the algorithm is the ability to analyze the propensity of the studied construction to progressive collapse based on the identification of stabilization states and subsequent calculation of its reliability indicators using a model of parallel connection of elements. Results. The article proposes a new method for the reasonable selection of a set of key most critical elements of spatial steel rod constructions. The use of this technique makes it possible to simplify and concretize the calculation of the construction for the tendency to progressive collapse. A method for determining the reliability indicators of spatial rod constructions of an increased degree of responsibility is proposed. The authors propose a methodology for determining the reliability indicators of spatial core constructions of an increased degree of responsibility. An algorithm for calculating reliability indicators of the constructions under consideration has been developed in the MATLAB programming language. The proposed methodologies have been tested on the example of a structural coating. The construction is square in plan and has a side length of 24 m. The cell of the core plate is made in the form of a pentahedron with a height of 3 m. A demonstration engineering calculation of the construction under consideration has been performed. According to the calculation results, the tendency to progressive destruction has been eliminated in the construction. The security characteristic increased from -1.54 to 2.67. This indicates an increase in the level of reliability of the core slab.