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  • Methods for determining the calculated lengths of centrally loaded steel columns when pivotally adjacent to reinforced concrete bases

    This article discusses several ways to determine the calculated lengths of steel columns in the plane of the frame. By analyzing existing techniques, the most successful method of selecting the calculated lengths for steel columns in a free multi-storey frame was determined. Taking into account the non-standard case of fastening crossbars to the considered section in the frame of the overpass, using the LIRA CAD PC, as well as the Crystal module (implemented in SCAD), the loss of stability of equally loaded elements in the most sensitive area is clearly shown.

    Keywords: Euler's formula, loss of stability, coefficient of calculated length, calculated length, coefficient of stability margin, finite elements

  • Changing the elastic characteristics of the base in depth

    Changes in the elastic characteristics of the soil for a base model that is inhomogeneous in depth are considered. The dependences of the modulus of elasticity of the soil and the coefficient of lateral pressure on the relative depth are obtained.

    Keywords: modulus of elasticity, lateral pressure coefficient, pressure, compression curve

  • Calculation of concrete elements in conditions of uneven all-round compression

    The cases of uneven compression of a concrete cylinder in the case of simple loading and comprehensive uneven compression of a spiral-reinforced concrete cylinder under disproportionate loading are considered. The dependences of longitudinal, transverse and volumetric deformations on longitudinal stress are obtained.

    Keywords: longitudinal stress, circumferential stress, longitudinal deformation, circumferential deformation, spiral reinforced concrete strut, shear strain intensity, shear stress intensity

  • Features of the construction of the gravity base of the offshore platform

    This article reveals a number of examples of the features of the construction of the base of a gravity offshore platform used for the extraction of hydrocarbons. The design of the reinforced concrete base of the platform in the form of a "monopod" consisting of 8 lower cylindrical tanks and a vertical reinforced concrete support with a length of 95 m is considered. Reinforcement of the entire structure was carried out by pre-tensioning reinforcement ropes on the hardened concrete in height by mechanical means. During the construction of the gravity foundation, new compositions of heavy high-strength modified concretes with the use of microsilicon and nanocarbon additives were used. During the construction process, adjustable formwork was used along the entire height of the structure.

    Keywords: gravity platform base, monopod, pre-tension on concrete, high-strength modified concrete, towing, positioning

  • The mechanism of loading of piece cargoes of cylindrical shape

    Currently, loaders for piece loads used in the technological process of loading-transporting and laying barrels of oil are widely used in industry. In particular cases, during loading and transport operations, the functionality of the loader is sufficient, but when laying cargo or obstacles occur, it is necessary to maneuver using the loader chassis, which significantly increases the execution time of the technological process. The results of the conducted studies have shown that when performing the technological operation of capturing, transporting and stacking barrels, the time to move the chassis is up to 12%, while the loader performance coefficient is 0.65. Numerical modeling of the positioning process of the load-handling body of the output link of the loading and transport unit is carried out, on this basis, a loader design based on a stacker is proposed and developed. The degree of mobility of the manipulation mechanism is calculated.

    Keywords: numerical modeling, loader, manipulator, hinges, chassis, structural analysis, degree of mobility, kinematic analysis, service area, lifting body, mechanism

  • Stress Concentration in Construction Elements of Polycrystalline Materials at Various Stress States

    The paper is concerned with relevant stress concentration research in construction elements made of structurally heterogeneous materials. On the base of the physico-mechanical model of structurally heterogeneous body (polycrystal) , with the use of finite elements method, stress distribution in construction elements made of polycrystalline metals with hexagonal lattice (magnesium, titanium, zinc) is investigated at various stress states. Coefficients of stress concentration in plates with circular holes are determined in the case of uniaxial tension, uniform biaxial tension, and pure shear. It is demonstrated that stress concentration coefficients calculated regarding microstructural factors of stress concentration can take values that considerably differ from values for isotropic body, depending on anisotropy of elastic properties of polycrystalline metals and a type of stress state

    Keywords: linear and plane stress states, polycrystalline structure, microstructural factors, nonuniformity of stress

  • Study on Stress Inhomogeneity in Finite Element Model of Polycrystal at Non-uniform Uniaxial Tension

    The paper deals with the results of study on the degrees of stress inhomogeneity caused by interaction between differently oriented crystalline grains in macrovolumes in case of non-uniform uniaxial tension. Calculation of finite element volume consisting of forty grains is performed. It has been revealed that the quantity of forty grains is enough for constituting the smallest body volume, which can be assumed to have the averaged properties of a macrovolume. Directions of crystallographic axes were selected randomly. Calculations were performed for various metals with cubic and hexagonal lattices. Based on the results of calculations, the curves of normal stresses in the central cross-section of the elementary volume were constructed. It has been found that the significant exceedance of normal stress values is possible in comparison to the values calculated for quasi-isotropic fine-grain material. Dependence between the degree of stress inhomogeneity and the degree of anisotropy of elastic properties has been demonstrated

    Keywords: microvolume, macrovolume, non-uniform tension, degree of stress inhomogeneity

  • Investigation stress concentration of construction elements of polycrystalline materials

    Structurally heterogeneous materials, in particular polycrystalline materials, have wide application in construction and technics. The higher values of local microstress in comparison to the average values of stress lead to the faster exhaustion of bearing capacity and destruction. Therefore, nonuniformity of microstress and microstrain depending on structure, physical and mechanical properties, should be taken in consideration when estimating bearing capacity, especially for the elements of construction with different stress concentrators. On the base of the physico-mechanical model of structurally heterogeneous body stress concentration for small-scale plates , made of polycrystalline materials with hexagonal lattice, with circular holes, at the case of uniaxial stress state, is investigated. It is shown that coefficients of stress concentration depending on anisotropy of elastic properties of polycrystalline materials can take values which considerably differ from values for isotropic body. Physico-mechanical model developed for structurally heterogeneous body allows studying local microstress in the construction elements at various stress states, with different forms and kinds of stress concentrators, which is the subject of the further research

    Keywords: stress distribution, structural heterogeneity of the material, polycrystalline metals,microstress and microstrain, stress concentration