Investigation of the stress-strain state of the foundation structure, taking into account the influence of elevated temperatures on the mechanical characteristics of high-strength steel fibre concrete

Introduction. The analysis of existing studies shows that elevated temperatures significantly alter the physical and mechanical properties of concrete, including high-strength steel fibre reinforced concrete, which reduces the reliability of calculation models for thermally loaded structures. The combined action of thermal and mechanical factors leads to variations in the strength and deformation characteristics of the material. In this context, structures operating under long-term thermal exposure are of particular practical interest. Continuous casting machines (CCM), which are the main metallurgical units for steel casting, require massive foundations operating under prolonged thermal effects, making the study of their mechanical characteristics highly relevant.

Materials and methods. The paper presents the test results of specimens made of high-strength steel fibre concrete with a fibre content of µsfb = 0 and 2.5 %. The influence of the percentage of fibre reinforcement and elevated temperatures on the basic mechanical characteristics of the material is estimated. Based on the data obtained, numerical modelling of the CCM foundation using the finite element method was performed using the diagrammatic calculation method, taking into account physical nonlinearity, real-world operating conditions and temperature conditions. The Lira-CAD 2020 software package was used for modelling, which takes into account the heterogeneity of temperature and shrinkage deformations and the actual deformation diagrams of the material.

Results. The parameters of the stress-strain state and the values of mechanical properties for high-strength steel fibre concrete are obtained, taking into account the duration of heating up to +200 °C. Numerical modelling has shown the influence of the heterogeneity of the temperature distribution over the volume of the structure on the stress-strain state of the studied elements. The use of high-strength steel-fibre concrete as a variable material made it possible to reduce the magnitude of tensile forces and stresses, as well as increase the crack resistance of the structure in question.

Conclusions. The introduction of up to 2.5 % steel fibre into the composition of high-strength concrete significantly increases its mechanical properties at normal temperatures. Experiments have shown that short-term heating reduces the strength and elastic characteristics, and prolonged temperature exposure changes the complex of physical and mechanical properties of the material. The analysis of the stress-strain state of the foundations confirmed the effectiveness of the use of high-strength steel-fibre concrete in conditions of thermal exposure.

1. Mishina A.V., Chilin I.A., Andrianov A.A. Physicotechnical properties of high performance steel fiber reinforced concrete. Vestnik MGSU [Proceedings of Moscow State University of Civil Engineering]. 2011; 3-2:159. EDN OWCDNF. (rus.).

2. Korsun V., Korsun A., Volkov A. Characteristics of mechanical and rheological properties of concrete under heating conditions up to 200 °C. MATEC Web of Conferences. 2013; 6:07002. DOI: 10.1051/matecconf/20130607002

3. Li P., Feng J., Gu J., Duan S. Coupled Effects of High Temperature and Steel Fiber Content on Energy Absorption Properties of Concrete. Materials. 2024; 17(14):3440. DOI: 10.3390/ma17143440

4. Agapov V.P., Markovich A.S., Dkhar P., Golishevskaia D.A. Stress-strain state of steel fiber-reinforced concrete under compression taking into account unloading from inelastic region. Structural Mechanics of Engineering Constructions and Buildings. 2024; 20(2):170-181. DOI: 10.22363/1815-5235-2024-20-2-170-181. EDN XTFTZA. (rus.).

5. Denisov A.V., Zaitsev D.V. Prediction of the resistance of steel fiber concrete to thermal effects at various parameters of dispersed reinforcement. Engineering Journal of Don. 2022; 5(89):433-472. EDN JQDVWK. (rus.).

6. Dyachuk E.V. Assessment of stress–strain state of reinforced concrete column with steel fiber reinforcement. Butakov Readings : collection of papers of the III All-Russian Youth Conference with international participation. 2023; 269-270. EDN QWDVDI. (rus.).

7. Dyachuk E.V. Characteristics and key indicators of steel fiber reinforced concrete for industrial applications. Power Engineering and Energy Saving: Theory and Practice : collection of Materials of the VIII International Scientific and Practical Conference within the framework of the Decade of Science and Technology in the Russian Federation. 2024; 133.1-133.3. EDN XTIXGG. (rus.).

8. Kapustin D.E. Dependence of the complete diagrams of deformation of steel fiber reinforced concrete under axial tension from the parameters of fiber reinforcement. Engineering Journal of Don. 2021; 7(79):473-485. EDN ZAQEAR. (rus.).

9. Korsakov N.V., Korsakova T.I. Analysis of du-rability of steel-fiber concrete structures under conditions of sign-variable temperatures. International Journal of Humanities and Natural Sciences. 2023; 6-3(81):122-126. DOI: 10.24412/2500-1000-2023-6-3-122-126. EDN IWWKWE. (rus.).

10. Mishina A.V. Change in the physical and mechanical properties of high-strength steel fibro concrete in the course of time. Building and Reconstruction. 2011; 6(38):70-74. EDN PAJHRV. (rus.).

11. Agapov V.P., Markovich A.S., Dkhar P., Golishevskaia D.A. Stress-strain state of steel fiber-reinforced concrete under compression taking into account unloading from inelastic region. Structural Mechanics of Enginee-ring Constructions and Buildings. 2024; 20(2):170-181. DOI: 10.22363/1815-5235-2024-20-2-170-181. EDN XTFTZA. (rus.).

12. Pukharenko Yu.V., Panteleev D.A., Zhavoron-kov M.I. Development of a method for testing the crack resistance of steel fiber reinforced concrete. Construction Economics. 2023; 9:132-137. EDN AABQGK. (rus.).

13. Rudnov V.S., Gerasimova E.S. Effect of the efficiency of dispersed reinforcement on the prismatic strength of heavy concretes. Engineering Journal of Don. 2020; 8(68):223-231. EDN RIOZXJ. (rus.).

14. Khegai A.O., Kirilin N.M., Khegai T.S., Khe-gai O.N. Experimental investigation of stress-strain properties of steel fiber reinforced concrete of the higher classes. Bulletin of Civil Engineers. 2020; 6(83):77-82. DOI: 10.23968/1999-5571-2020-17-6-77-82. EDN NTWMLK. (rus.).

15. Abadel A. Residual compressive strength of plain and fiber reinforced concrete after high-temperature exposure. International Journal of Concrete Structures and Materials. 2022; 16:48.

16. Abdi Moghadam M., Izadifard R.A. Prediction of the Tensile Strength of Normal and Steel Fiber Reinforced Concrete Exposed to High Temperatures. International Journal of Concrete Structures and Materials. 2021; 15(1). DOI: 10.1186/s40069-021-00485-6

17. He F., Biolzi L., Carvelli V., Feng X. A review on the mechanical characteristics of thermally damaged steel and polypropylene hybrid fiber-reinforced concretes. Archives of Civil and Mechanical Engineering. 2024; 24(2). DOI: 10.1007/s43452-024-00880-2

18. He X., Xiang W., Peng X., Dan Y. Axial Compression Performance and Residual Strength Calculation of Concrete-Encased CFST Composite Columns Exposure to High Temperature. Applied Sciences. 2022; 12(1):480. DOI: 10.3390/app12010480

19. Khalil W.I. Influence of High Temperature on Steel Fiber Reinforced Concrete. Journal of Engineering and Development. 2006; 10(2):139-144.

20. Liang J., Liu K., Wang C., Wang X., Liu J. Mechanical properties of steel fiber-reinforced rubber concrete after elevated temperature. Scientific Reports. 2025; 15(1). DOI: 10.1038/s41598-024-80458-3

21. Zhang P., Kang L., Wang J., Guo J., Hu S., Ling Y. Mechanical Properties and Explosive Spalling Behavior of Steel-Fiber-Reinforced Concrete Exposed to High Temperature : а Review. Applied Sciences. 2020; 10(7):2324. DOI: 10.3390/app10072324

22. Tamrazyan A.G. Analysis of the behavior of spirally reinforced high-strength concrete columns under central compression. Reinforced Concrete Structures. 2025; 11(3):3-20. DOI: 10.22227/2949-1622.2025.3.3-20. EDN CECGTG. (rus.).

23. Kharun M., Klyuev S., Koroteev D., Chiadig-hikaobi P.C., Fediuk R., Olisov A. et al. Heat Treatment of Basalt Fiber Reinforced Expanded Clay Concrete with Increased Strength for Cast-In-Situ Construction. Fibers. 2020; 8(11):67. DOI: 10.3390/fib8110067

24. Kalmykov Yu.Yu. Stressed-deformed state of a reinforced foundation element at uneven heating. Modern Industrial and Civil Construction. 2007; 3(1):37-44. EDN LALBHT. (rus.).

25. Korsun V., Mashtaler S. The influence of high temperatures up to 200 °C characteristics of physical and mechanical properties of high-strength steel fiber reinforced concrete. Fundamental, exploratory and applied research of the Russian Academy of Architecture and Construction Sciences on scientific support for the development of architecture, urban planning and the construction industry of the Russian Federation in 2017 : collection of scientific papers of the Russian Academy of Architecture and Construction Sciences. 2018; 2:265-274. DOI: 10.22337/9785432302663-265-274. EDN ODYUFO. (rus.).

26. Korsun V.I. Stress–strain state of reinforced concrete structures under thermal exposure. Makeyevka, DonGASA, 2003; 153. (rus.).