Аналіз технічного стану балконних конструкцій житлового фонду україни та теоретичне обґрунтування використання тонкостінних залізобетонних балок для їх відновлення

Abstract

The article considers the complex problem of ensuring the reliability and reconstruction of balcony systems of the housing stock of Ukraine in the conditions of exhaustion of their normative operational resource and mass destruction due to armed aggression. Taking into account irreversible changes in the stress-strain state and a decrease in the residual bearing capacity of damaged wall enclosures, the feasibility of transitioning traditional massive cantilever slabs to lightweight resource-efficient systems based on thin-walled reinforced concrete beams (with a cross-sectional width of b = 30...40 mm and a ratio of h/b > 5) is substantiated. Since the use of elements with a high cross-sectional aspect ratio is accompanied by a critical risk of sudden loss of spatial stability of the flat bending shape even before the strength of the materials is exhausted, the paper proposes an improved nonlinear analytical method for their calculation. The calculation apparatus is based on the use of an energy approach to determining the deformability of a bending element at the stage of crack formation. The developed mathematical model is based on the concept of the full energy invariant of shear deformation, which allows to reliably estimate the effective torsional stiffness of the section by its harmonic averaging taking into account the local Nagel effect of the longitudinal reinforcement. The study adapted the classical Prandtl-Vlasov stability criterion to the conditions of a physically nonlinear reinforced concrete composite. The presented practical engineering calculation of a thin-walled beam confirms the safety and effectiveness of the proposed solution. Analysis of the obtained data shows that the relative deviation of the value of the ultimate bending moment, calculated using the modified method of design resistances, the reference indicators of the classical method does not exceed 2.7%. The results of the study form a reliable theoretical basis for the design and implementation of innovative beam systems in the process of renovation and post-war reconstruction of residential infrastructure.