This paper reports a study into the effect of the winding type on the stressed-strained state of the wall of a steel cylindrical tank filled with oil to the predefined level. The shapes of free oscillations of oil in the tank and the effect of the winding type on the natural frequencies of the structure were analyzed. Stress in the tank wall was estimated on the basis of finite-element simulation of the deformation of a three-dimensional structural model under the influence of distributed oil pressure on the inner surface of the wall and stresses on the outer surface of the wall. The stresses were induced by the winding of various types, taking into consideration the level of oil loading, the winding step of the winding, and the mechanical characteristics of the thread. The stressed-strained state of a cylindrical tank with winding was investigated at its full filling with oil, half-filling with oil, and without oil. Three winding options were simulated: single, double, and triple intervals. Two types of winding were considered: made from high-strength steel wire and made from composite thread. It was established that when winding the tank wall with steel wire at a triple interval, the stress in the structure does not exceed 34.2 % of the yield strength. At the same time, the height of oil loading does not significantly affect its strength. Applying a composite thread leads to an increase in the stress of up to 47.2 % of the yield strength but makes it possible to reduce the mass of the tank with winding. When winding with a composite thread at a triple interval, the mass of the structure increases by only 3.6 %. The results reported here make it possible to effectively use pre-stress in order to improve the strength and dynamic characteristics of the studied structures, taking into consideration their windings made of different materials

A multi-level mathematical model was used to estimate the stressed-strained state of a cylindrical reservoir with a defect in the wall shape in the form of a dent; the concentration of stresses in the defect zone was studied. The proper choice of the mathematical model was verified; it has been shown that the engineering assessment of the stressed-strained state of the wall of a cylindrical tank with the variable thickness could employ ratios for a cylindrical shell with a constant wall thickness. The spread of values is 2‒10 %. This indicates the proper choice of the mathematical model, as well as the fact that it is possible, for an engineering assessment of the stressed-strained state of the wall of a cylindrical tank with variable thickness, to use the ratios for a cylindrical shell with a constant wall thickness. The stressed-strained state of the dent zone in the tank wall was numerically estimated, which proved the assumption of significant stress concentrations in the dent zone and indicated the determining effect on the concentration of stresses in the dent zone exerted by its geometric dimensions and its depth in particular. The concentration of stresses in the zone of dents in the tank wall was investigated in the ANSYS programming environment at different sizes of dents on the tank wall, for which two dimensionless parameters were introduced: the dimensionless radius of the dent and the dimensionless depth of the dent. Based on the results of a numerical study into the stressed-strained state of the dent zone in the tank wall, graphic dependences were derived of the stress concentration coefficient on the dimensionless depth of the dent for various values of the dimensionless radius of dents, which does not exceed 2 % of the indicator. Based on fitting the stress concentration curves on the dimensions of the dent and tank, a formula was derived for calculating the stress concentration coefficient as a function of the dimensionless radius ξ and the dimensionless depth ς of the dent. The resulting formula makes it possible, with known dimensionless parameters of the depth and radius of the dent, to determine the coefficients of stress concentration in the dented zone of the tank wall.

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This paper reports an analysis of the frequencies and shapes of oscillations of the tank with a volume of 3000 m3 with a winding of high-strength steel wire with a diameter of 3 mm, 4 mm, and 5 mm, applied in increments of 1:3. In addition, for the tension force of the turn in the range from 0.2 to 0.8 of the yield strength of the wire material. The study was carried out on the basis of a finite-element method in the ANSYS software package for a three-dimensional geometric model of the structure. At the same time, the software took into consideration the height-uneven width of the cylindrical wall taking into account the height of the filling to the maximum height and the tension forces of the winding. It has been established that a change in the diameter of the winding wire does not lead to a significant change in the spectrum for the first ten significant frequencies. And an increase in the tension force of the wire in the winding leads to a decrease in the magnitude of oscillation frequencies. The exception is the sixth frequency. Its values are equal to one-tenth of a Hz for all estimated cases of the force of tension of the turn in the range from 0.2 to 0.8 of the yield strength of the wire material. The oscillation shapes of the tank reinforced by the winding have been determined. The change in the tension force of the wire in the winding does not change the number of waves at the circumferential coordinate at the free edge of the structure. We studied the loss of stability of the tank wall under distributed internal pressure. A comparative analysis of the sixth oscillation shape and the shape of stability loss reveals that they have the same number of waves at the circumferential coordinate. The results reported here could make it possible to effectively use the pre-stress in order to detune the tank from the resonant frequency when operating in seismically hazardous areas

This paper considers the structural solution for a main above-ground pipeline with a pre-stressed winding, which makes it possible to improve the efficiency of operation and reduce material consumption. The results from studying experimentally the features in the operation of prestressed pipelines under static operating loads are given. It is shown that the radial movements of the wall of a pre-stressed pipeline are constrained by the strained winding, which prevents its deformation. It was revealed that increasing the tension force of the winding wire reduces circular stresses in the pipeline wall by 1.3...1.6 times and increases meridional ones by 1.2...1.4 times. The experimental study into the models of prestressed pipelines with free vertical and horizontal oscillations has established the dependence of frequency characteristics on the operating conditions and pre-stress parameters. It was found that the envelope amplitude on the oscillogram of free attenuated oscillations takes the shape of an exponent, which indicates the damping effect of the pre-stress. Analysis of the change in the dynamic characteristics of the models depending on the pre-stress force has revealed that the frequencies of free oscillations increase by 1.5÷1.6 times while the oscillation decrement decreases by 1.2÷1.25 times. This paper reports the results of studying the influence of pre-stress parameters on the stressed-strained state of the pipeline model under forced horizontal and vertical oscillations. It is shown that the diagrams of circular dynamic stresses and deformations in the models of a prestressed pipeline are smoother compared to similar characteristics of a conventional pipeline tested at the same experimental parameters. The study results have made it possible to quantify the features in the operation of a pre-stressed pipeline under static and dynamic influences, taking into consideration the pre-stress parameters and operating conditions.