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This study examines the influence of the reinforced-concrete frame topology and crack opening effects on the structural behavior under a column removal scenario. For this purpose, a variant of discretization of the finite element model has been proposed, which takes into account additional rotations during the formation of discrete cracks. As a criterion of the bearing capacity of structures, the equilibrium point at the force-displacement curve was adopted. Verification of the proposed method has been performed using experimental data for a U-shaped frame. The paper provides a comparative analysis of the calculation results for 3-story, 5-story and 9-story reinforced-concrete frames using structural elements and the proposed method. It is found that accounting for the discrete nature of cracks had practically no effect on the magnitudes of axial forces in the elements. However, for bending moments, the proposed method showed a decrease compared to the traditional approach. The increase of axial tensile forces in the support sections of the beam above the zone of local failure has been detected for reinforced-concrete frames with 3 - 5 stories, which can lead to an increase in the influence of buckling for the columns to which such a beam is adjacent. [ABSTRACT FROM AUTHOR]

A possible way to improve the structural safety and robustness of precast building structures is to develop effective precast frame systems with layered beams, which combine prefabricated parts with cast-in situ ordinary concrete, high-performance concrete, fiber concrete, or FRP. The paper provides a new type of precast reinforced concrete frame system with layered beams for rapidly erected multi-story buildings resistant to accidental actions. Using a combination of the variational method and two-level design schemes, a simplified analytical model has been developed for structural analysis of the precast reinforced concrete frame system, both for serviceable and ultimate limit states as well as for accidental actions. The proposed model allows for determining shear deformations and the formation and opening of longitudinal cracks in the intermediate contact zone between precast and monolithic parts of reinforced concrete structural elements of the frame, as well as the formation and opening of normal cracks because of the action of axial tensile force or bending moment in these elements. The design model was validated by comparing the calculated and experimental data obtained from testing scaled models of the precast reinforced concrete frame system with layered beams. The paper investigates and thoroughly analyzes the factors affecting the stiffness and bearing capacity of the intermediate contact zone, discusses the criteria for the formation of shear cracks along the contact zone of precast and monolithic concrete, and examines the change in the stiffness and dissipative properties of layered elements at different stages of their static–dynamic loading. The robustness of the experimental models of the structural system was not ensured under the specified load, section dimensions, and reinforcement scheme. Following an accidental action, longitudinal cracks were observed in the contact joint between the monolithic and prefabricated parts in the layered beams. This occurred almost simultaneously with the opening of normal cracks in adjacent sections. A comprehensive analysis of the results indicated a satisfactory degree of agreement between the proposed semi-analytical model and the test data. [ABSTRACT FROM AUTHOR]