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Chepurnenko A.S.

Doctor of Engineering Sciences (Advanced Doctor), Professor, Don State Technical University, Department «Structural Mechanics and Theory of Structures», Russia

Experience of concreting a massive monolithic foundation slab

https://doi.org/10.58224/2618-7183-2025-8-5-2
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Abstract
The large number of recipe and technological factors affecting the stress-strain state of concrete in the initial period of massive monolithic structures erection predetermines the expediency of using modeling of temperature fields and stresses with software packages based on analytical and numerical solutions when developing technological regulations for concreting. Improving the algorithm for calculating temperature fields and stresses taking into account the kinetics of concrete heat release, heat exchange conditions, ambient temperature and the stages of construction of structures is a pressing task. A comparison was made of calculated, laboratory and natural values of some parameters when concreting a foundation slab with a volume of 1642 m3, a surface area of 821 m2, and a thickness of 2 m. Concreting was completed in 13.5 hours with an average intensity of concrete mix placement of 122 m3/h, and a peak intensity of up to 240 m3/h. A method for calculating temperature fields and stresses taking into account the staged nature of construction has been developed in the MATLAB environment. It does not require rebuilding the geometry of the finite element model, adding nodes and elements during the process of laying new layers, and allows for the correct consideration of the dependence of the strength and deformation properties of concrete on the degree of its maturity. The results of calculated and measured temperature values excluding heating from solar radiation showed a discrepancy of up to 10 °C on the upper surface at some points in time. Some discrepancy between the calculated and experimental values of stresses and deformations with a qualitative coincidence in the nature of the curves is due to the neglection of shrinkage and rapid creep of concrete and poor study of the deformation properties of concrete with additives based on polycarboxylate esters at an early age.
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Predicting the risk of early cracking in massive monolithic foundation slabs using artificial intelligence algorithms

https://doi.org/10.58224/2618-7183-2025-8-1-6
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Abstract
The article presents a study of the application of artificial intelligence algorithms in predicting the risk of early cracking in massive reinforced concrete structures using monolithic foundation slabs as an example. The current experience of using algorithms such as convolutional neural networks, deep learning tools (YOLOv5 model) for crack detection at various stages of the life cycle of massive reinforced concrete structures is analyzed. The causes of crack formation, physical and mechanical processes, including cement hydration are considered.
A model has been developed that predicts the magnitude of the tensile stress level in monolithic foundation slabs during construction, based on CatBoost using Python, allowing to predict the risks of early cracking with an accuracy of up to 98%.
The model was trained on synthetic data containing various design parameters and material properties, including the geometric dimensions of the slabs, the temperature on the upper surface, the heat transfer coefficient on the upper surface, the curing rate, the class of concrete and the characteristics of the soil base. Statistical analysis of the data was performed, a correlation matrix was constructed. Practical and predicted values of the model were visualized in the form of a scatter plot. The most significant parameters influencing the risk of early cracking in massive monolithic foundation slabs were obtained. The constructed model passed quality assessment according to three metrics: MAE=0.0011; MSE=4.038; MAPE=0.0014.
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Methodology for determining true temperature stresses during the construction of massive monolithic reinforced concrete structures

https://doi.org/10.58224/2618-7183-2024-7-3-5
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Abstract
The purpose of the article is to develop and test a simplified method for calculating temperature stresses during the construction of massive monolithic reinforced concrete structures. The essence of the method is to calculate the stress-strain state in standard FEM complexes (ANSYS, Abaqus , etc.) with constant physical and mechanical characteristics of concrete over time, followed by recalculation to true stresses, taking into account the dependence of the elastic modulus of concrete over time. The methodology is based on the hypothesis of equality of temperature deformations for structures with a constant and time-varying modulus of elasticity of concrete. The developed
methodology was tested on experimental data for a massive monolithic foundation slab. The calculation at a constant modulus of elasticity of concrete was carried out in the ANSYS software package. Conversion to true stresses was implemented by the authors in the MATLAB environment. A good agreement between the calculated stress values and the experimental values was obtained.
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Artificial intelligence model for predicting the load-bearing capacity of eccentrically compressed short concrete filled steel tubular columns

https://doi.org/10.58224/2618-7183-2024-7-2-2
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Abstract
The purpose of this work is to develop the artificial neural network (ANN) model to determine the load-bearing capacity of concrete filled steel tubular (CFST) columns of circular cross-section in a wide range of input parameters. Short columns are considered for which deflections do not lead to a significant increase in the eccentricity of the axial force. The input parameters of the artificial neural network are the outer diameter of the pipe, the wall thickness, the yield strength of steel, the compressive strength of concrete, and the relative eccentricity of the axial force. The artificial neural network is trained on the synthetic data. For training, the dataset of 179,025 numerical experiments with different values of input parameters was generated. Numerical experiments were carried out using the finite element method in a simplified formulation, which makes it possible to reduce the three-dimensional problem of determining the stress-strain state of a CFST column to a two-dimensional problem. The results of testing the developed model on the data from full-scale experiments are pre-sented.
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Processing of nonlinear concrete creep curves using nonlinear optimization methods

https://doi.org/10.58224/2618-7183-2024-7-1-2
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Abstract
The article proposes a method for determining the rheological parameters of concrete based on creep curves at various stress levels using the theory of V.M. Bondarenko. Using the proposed methodology, the experimental data presented in the work of A.V. Yashin is processed. The problem of searching for rheological parameters is posed as a nonlinear optimization problem. The sum of squared deviations of the experimental values of creep strains from the theoretical ones is minimized. The interior point method is used as a nonlinear optimization method. Four different expressions for the creep measure are considered, including the creep measure by N.Kh. Harutyunyan, creep measure by A.G. Tamrazyan, a creep measure in the form of a sum of two exponentials, and McHenry’s creep measure. It has been shown that the best agreement with experimental data is provided by the McHenry’s creep measure. An expression has been selected for the nonlinearity function, which describes the nonlinear relationship between stresses and creep strains. It is shown that the instantaneous nonlinearity of deformation and the nonlinearity that manifests itself over time cannot be described by a single function.
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Optimization of Rectangular and Box Sections in Oblique Bending and Eccentric Compression

https://doi.org/10.58224/2618-7183-2023-6-5-2
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Abstract
The article presents a solution to the problem of finding the optimal ratio of the height of the cross-section to the width for a rectangular and box-shaped section in the case of oblique bending and eccentric compression. Optimization is performed according to the strength criterion, and for the case of oblique bending of a rectangular beam, a solution was also obtained from the condition of a minimum full deflection. For a rectangular section, the solution is made analytically, and for a box section, numerically using the MATLAB environment and the Optimization Toolbox package. As a numerical method of nonlinear optimization, the interior point method is used. To simplify the solution, the box section is assumed to be thin-walled, i.e. it is assumed that the wall thickness is significantly less than the height and width of the cross section. An estimate of the error of such an assumption is also performed. It has been established that in the case of oblique bending of a rectangular beam, when optimizing according to the strength criterion, the optimal ratio of the cross-sectional height to width is equal to the cotangent of the angle between the force plane and the vertical axis, and when optimizing according to the rigidity criterion, it is the square root of the cotangent of this angle. In the case of eccentric compression of a rectangular beam with eccentricities in two planes, the optimal ratio of the height of the cross section to the width is equal to the ratio of the eccentricity along the vertical and horizontal axes. For a box-shaped section, graphs of the change in optimal parameters depending on the angle between the force plane and the vertical axis in the case of oblique bending, as well as depending on the ratio of eccentricities along the axes in the case of eccentric compression, are plotted.
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