In order to study the cracking of prestressed reinforced concrete T-shaped beam structures, the authors planned and carried out a full-scale experiment with five variable factors. The following factors were chosen as variable factors: the relative span of the shear, the ratio of the table overhang width to the thickness of the beam rib, the ratio of the table overhang thickness to the working height of the beam section, the coefficient of transverse reinforcement, the level of prestressing in the working reinforcement. The article describes the cracking process and the destruction of test beams. It was found that the loading level of an opening of inclined cracks is 53% larger than the loading level of a normal crack opening. Mathematical models of bending moments and transverse forces of cracking were built using the “COMPEX” software. Also, the mathematical models of the crack opening width and the projection length of a dangerous inclined crack were obtained. These models are based on the experimental data. Analysing the obtained models, the complex influence of variable factors on the main parameters of crack formation and crack resistance was established. In particular, it was found that the prestress level in the working reinforcement has the greatest effect on the bending moment of cracking. In this case, the value of the shear force of cracking significantly depends on both the prestressing level in the reinforcement and the relative span of the shear. On the basis of the experimental data, the empirical expression is obtained for determining the projection of a dangerous inclined crack for prestressed reinforced concrete T-shaped beams. The resulting equation can be used to calculate a shear reinforcement.

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Волкова Анастасія Сергіївна, аспірант кафедри будівельних, колійних та вантажно-розвантажувальних машин Українського державного університету залізничного транспорту.

The paper deals with the working peculiarities of the support zones of reinforced concrete elements subject to bending with due account of the eccentric compression and tension. The authors performed simulation of the stress-strain behaviour of the indicated structures with the aid of “Lira” software which results are shown in the graphical and tabulated form. The performed simulation allowed of tracing the work of the studied sample beams till collapse. Such approach made it possible to single out and generalize the main collapse patterns of the inclined cross-sections of the reinforced concrete elements subject to bending on which basis the authors developed the improved method to calculate their strength (Karpiuk et al., 2019).

The engineering method of analysis of pressure of a ground on flat walls is offered at presence of combine strip superficial loading in view of seismic influences. It is recommended to determine a situation of an internal slip surface dividing an elastic zone from area of limiting balance, on the basis of the technical theory of the ultimate stress condition. Proceeding from a situation of an internal and external slip plane, size of strip loading on the fill, the pressure of a ground which is taking place in an ultimate condition, on an internal slip surface of is determined on developed by P. Yakovlev to the specified Coulomb's method [1], and on an internal side of a retaining structure on the basis of the Boussinesq decision. In comparison with the earlier developed way it is offered specified according to the Boussinesq theory a method of definition of pressure transmitted by bed on a ground of the basis and, as a consequence more reasonable definition of safety factor of stability of a structure. Thus, curvilinear normal pressure diagram in a ground under a sole of lay is replaced on isosides trapeziform.