The article presents the results of a numerical experiment consisting in a bending test of a reinforced concrete beam and comparison of the results obtained with the results of full-scale experiments. In most cases, it is not possible to adequately consider all types of nonlinearities when using simplified bar and plate elements. The problem can be solved by using more detailed computational models with solid finite elements, allowing to consider directly the joint behavior of reinforcing bars and concrete. The studies were carried out in the LS-DYNA software package, which implemented the nonlinear concrete model – Continuous Surface Cap Model (CSCM). This model allows to consider the joint behavior of reinforcing bars and concrete, using bar (for reinforcing bars) and solid (for concrete) finite elements, thereby helping to overcome existing shortcomings in the diagrams of concrete behavior. As an object of modeling, a reinforced concrete statically determinable beam of rectangular section with dimensions of 1,000 х 50 х 100 (h) mm is considered. The conducted studies showed that the ultimate load on the beam based on the results of numerical modeling is quite consistent with the experimental value (8.5% discrepancy). The arrangement of cracks and the fracture pattern obtained from the modeling results in the LS-DYNA software package are in good agreement with the results of the tests. The LS-DYNA software package will allow correct solid modeling of bending reinforced concrete elements with specification of nonlinear diagrams of concrete and reinforcing bars deformation and can be used for research, calculation and design of reinforced concrete elements of buildings and structures.

Relevance. The choice of adequate models of materials and deformation diagrams is of great importance when performing structural calculations in a nonlinear setting. Since there are no instructions on how to use the deformation diagrams of concrete and reinforcement when working together, given in SP 63.13330.2018, it is necessary to introduce assumptions for modeling reinforced concrete structures with finite elements of the same type. The aims of the work are to conduct numerical experiments on testing concrete cylinders for uniaxial compression and to verify the results with normative data. Methods. Numerical experiments were performed in the LS-DYNA software package. This program complex allows to simulate the joint work of concrete and reinforcement with the help of volume (for concrete) and rod (for reinforcement) finite elements. A cylinder with a diameter of 150 mm and a height of 300 mm was taken as model. Samples were modeled by volumetric finite elements. The CSCM - Continuous Surface Cap Model is a nonlinear material used to model concrete. Tests were carried out with samples of the following classes of concrete for cylindrical compressive strength: C12, C16, C20, C25, C30, C35, C40, C45, C50, C55. This corresponds to the following classes of cubic compressive strength: B15, B20, B25, B30, B37, B45, B50, B55, B60, B67. Results. The conducted researches have shown that the character of destruction of samples at numerical experiment corresponds to the character of destruction at tests. The investigated concrete model CSCM can be used in the calculation of concrete and reinforced concrete structures for the main classes of concrete, when taking into account the transition from cubic to prismatic strength and additional correction factors to cylindrical strength.

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