Fundamental issues of the strength of reinforced concrete slabs during punching

Introduction. The calculation model of the strength of slabs during punching, adopted in domestic regulatory documents, contains a number of contradictions to the physical side of the process. So it is known from experience that even before the moment of destruction, many cracks develop in concrete. Therefore, its tensile strength, which is the basis of the current model, is exhausted long before the destruction of the structure. The current model does not take into account the longitudinal reinforcement of the slabs, which is one of the main factors in ensuring strength during penetration. There are similar disadvantages in foreign models. The accuracy of normative calculation methods, both domestic and foreign, is low. Aim. Creation of a method for calculating of the slabs for punching, which correctly takes into account all known features of the structure and has high accuracy. Materials and methods. The method of calculating of the strength of slabs for penetration is considered, which is based on the condition of equilibrium of moments of external and internal forces, in contrast to the normative method, which considers the equilibrium of projections of all forces on the vertical axis. Results. A calculation method has been developed that does not contradict the known experimental data on the operation of slabs during punching. It was possible to correctly take into account the work of the longitudinal reinforcement of the slab. The high accuracy of the proposed calculation method is shown. Conclusions. The conducted research allows us to take a fresh look at the essence of the punching process. The mechanism of destruction, which has fundamental differences, is considered. The proposed calculation method allows us to obtain results comparable in accuracy with the best numerical models.