Vol 19, No 1 (2023)

The authors present a refined method of determining the moment of cracking in reinforced concrete bar constructions using the diagram of deformation of concrete built on the basis of the deformation theory of plasticity by G.A. Geniev in which the stress and strain invariants of concrete are linked by nonlinear dependences. In the resulting defining equations, the hypothesis of flat sections, as well as the premise of reaching the limit values of concrete deformations on the stretched fibers of the cross-section are used. Stresses in concrete are determined through deformation values in accordance with the nonlinear deformation diagram of concrete. On the basis of the assumptions accepted, analytical dependences for determining the moment of cracking in the sections of bending elements with single and double reinforcement have been acquired. The formulas obtained were used in the analysis of various factors influence on crack resistance of bendable reinforced concrete elements. It was found out that the moment of crack formation practically does not change when percentage of reinforcement of longitudinal tensile or compressed reinforcement changes. The most effective method of crack resistance improvement is the increase of concrete strength. The proposed methodology is verified by comparison with experimental results on reinforced concrete prototypes. It is concluded that the use of the diagram of nonlinear deformation of concrete on the basis of the theory of plasticity by G.A. Geniev allows to estimate more strictly the crack resistance of reinforced concrete rod elements.

The authors present theoretical basis for creating software for operational (on-site testing) experimental determination of the possibility of safe passage of heavy vehicles on road bridges, taking into account their actual operational condition with experimental confirmations. The features, conditions of use, and benefits of the software under development are expanded upon. The creation of the software is driven, on the one hand, by the need to ensure the safety of the driver and the bridge structure, and on the other hand, the need to assess the load capacity of the superstructures of road bridges according to the parameters of their stress-strain state to ensure guaranteed safe passage of heavy vehicles. The developed software for the operational determination of the possibility of safe passage of heavy vehicles on road bridge structures, with the consideration of their actual operational condition, is implemented using a personal computer. The software provides an assessment of the possibility of heavy vehicle passage through split and non-split systems of any length, considering the actual operational condition of the systems, while allowing to safely use any mobile load as a point of reference. The introduced software will be used as part of an upgraded system for rapid assessment of the load capacity of road bridges, developed on the basis of the SI-PPM measurement system with the addition of technical devices that increase the possibility of operational assessment of the load capacity of road bridges.

The aim of the study is to solve the problem of the stress-strain state of a thin ring under radial and ring loads, factoring in the radial inhomogeneity of the ring. Also, the task is to compare the two calculation methods to the example of solving the problem of uneven load distribution along the outer surface of the ring with one-dimensional inhomogenuity. Analytical or numerical-analytical solutions are used in the two-dimensional plane problem of the theory of elasticity in polar coordinates for an inhomogeneous body. Most of these problems consider centrally symmetric circular bodies. As a rule, this is possible when all unknown functions depend on the radius. These tasks correspond with the majority of ring and cylindrical structures. Pipes are suitable for creating pipeline systems and civil engineering, they are used for gas pipelines, in heating networks and water supply systems. The key feature of the work lies in the consideration of uneven radial and ring loads distribution along the outer surface of the ring. Comparison of the calculation results obtained by two methods makes it possible to determine the stressed and deformed states with sufficient accuracy, an indicator of which is the obtaining of the ring stresses.

Method for calculating the statics and dynamics of curved rods, based on the equations for a rectilinear rod, is described and justified in detail. Bernoulli's hypotheses and the variational method are applied. The main advantage and special feature of these formulas is that the simplest formulas that are valid for rectilinear rods are used for the calculations of curved rods. These formulas do not contain parameters characterizing the curvatures of the longitudinal axis of the rod. This feature is an essential factor in the calculation of curved rods, where the information about their longitudinal axis is given discretely, since no special methods of approximation of discretely given data are required, which enable to obtain information about the radius-vector of the rod longitudinal axis and its derivatives with the required high accuracy. Solutions of test static and dynamic problems are provided. Bending of a rod with a longitudinal axis in the form of a circle, a naturally twisted rod, and a spring fluctuation are considered. Comparison of the calculation results with the data published in the literature illustrates the reliability and high accuracy of the solutions obtained.

The author presents the results of a study of the geometry and stress-strain state of a surface with a frame of three flat curves in coordinate planes, which have found application today mainly in the shipbuilding industry. The purpose of the work is to identify from the point of view of the stress-strain state from the action of a constant uniformly distributed load the most optimal shell of a diagonal transfer of a velaroidal type with the same main frame of three superellipses. The static calculation was performed using the SCAD program based on the finite element method, designed to perform strength calculations of various types and purposes of structures. The influence of parametric equations for defining a surface depending on the generative family of the same type of cross sections on the distribution pattern of normal stresses and bending moments is shown. The results obtained can help architects and designers with choosing the shape of shells for new projects.

In the 1950s, the construction of hydropower facilities began in the regions of Siberia and the Far East, characterized by harsh climatic conditions, which should be taking into account to predict the stress state of dams. The aim of the study is an assessment of the conditions for the formation of temperature cracks in concrete dams and their influence on the further operation of the structure, as well as measures and technologies to combat cracking in massive concrete. Thermal stresses often exceed the stresses caused by the action of external loads and lead to the appearance of cracks in the concrete. Almost all modern concrete dams are subject to thermal cracking today. Appropriate design and technological measures must be provided for. When studying the thermally stressed state of lightweight concrete dams, the method of direct reproduction of thermal deformations on models made of brittle materials and computational methods oriented towards computer methods of solving problems are used. The results of modeling and computational studies of massive buttress dams are presented and the influence of the main influencing factors is considered, taking into account the effect of cracking on the operation of such dams.