The paper presents the results of an experimental investigation into the stress–strain state of an reinforced concrete (RC) slab subjected to two concentrated forces. The relevance of the study is driven by the need to refine the deformation characteristics of thin slabs experiencing large deflections. The aim of the research is to analyse the evolution of strains in concrete and reinforcement at various loading stages up to failure. The digital image correlation method was employed to measure displacements and strains. The tests established that the bending moment corresponding to the attainment of the limiting deflection is Muls=1.18 kN·m; at this stage, strains in the compressed concrete zone remain at a relatively low level. Immediately prior to failure, a redistribution of deflections along the span and localisation of strains in the vicinity of one of the applied forces were recorded. The obtained results confirm the effectiveness of the DIC method for analysing the stress–strain state of RC slabs.
Dong, Y. L., & Pan, B. (2017). A review of speckle pattern fabrication and assessment for digital image correlation. Experimental Mechanics, 57(8), 1161-1181. https://doi.org/10.1007/s11340-017-0283-1
https://doi.org/10.1007/s11340-017-0283-1
Dutton, M., Take, W. A., & Hoult, N. A. (2014). Curvature monitoring of beams using digital image correlation. Journal of Bridge Engineering, 19(3), 05013001. https://doi.org/10.1061/(ASCE)BE.1943-5592.0000538
https://doi.org/10.1061/(ASCE)BE.1943-5592.0000538
Firsov, T., Krul, Y., Potapov, S., Matiushchenko, M., & Torma, N. (2023). Analysis of determination methods of stress-strain state of concrete structures under temperature influences. Municipal Economy of Cities, 3(177), 51-56. https://doi.org/10.33042/2522-1809-2023-3-177-51-56
https://doi.org/10.33042/2522-1809-2023-3-177-51-56
Hernández-Pérez, J., Pascual-Francisco, J. B., López-González, A., Jiménez-Montoya, A., & Susarrey-Huerta, O. (2025). Flexural behavior of concrete slabs reinforced with embedded 3D steel trusses. Buildings, 15(13), 2144. https://doi.org/10.3390/buildings15132144
https://doi.org/10.3390/buildings15132144
Hoult, N. A., Take, W. A., Lee, C., & Dutton, M. (2016). Measuring crack movement in reinforced concrete using digital image correlation. Proceedings of the IEEE, 104(8), 1535-1548. https://doi.org/10.1109/JPROC.2016.2561212
https://doi.org/10.1109/JPROC.2016.2535157
Hu, W., Sheng, Z., Yan, K., Miao, H.,& Fu, Y. A (2021) New Pattern Quality Assessment Criterion and Defocusing Degree Determination of Laser Speckle Correlation Method. Sensors, 21, 4728. doi:10.3390/s21144728
https://doi.org/10.3390/s21144728
Khai, L. T. Q. (Lam Thanh Quang Khai), & Oanh, H. T. K. (Huynh Thi Kim Oanh). (2025). Experimental research on reinforced concrete slabs with loads from column placed on the slab. Journal of Materials & Construction, 15(1), 38-42. https://doi.org/10.54772/jomc.v15i01.926
https://doi.org/10.54772/jomc.v15i01.926
Klym, A., & Blikharskyy, Y. (2024). Methodology for the application of the digital image correlation (DIC) for investigating RC beams. Theory and Building Practice, 6(2), 69-80. https://doi.org/10.23939/jtbp2024.02.069
https://doi.org/10.23939/jtbp2024.02.069
Klym, A., Blikharskyy, Y., Blikharskyy, Z., Selejdak, J., & Panchenko, O. (2025). Stress-strain state of RC beams after restoration of the compressed concrete zone. In IOP Conference Series: Earth and Environmental Science (Vol. 1499, No. 1, 012030). IOP Publishing. https://doi.org/10.1088/1755-1315/1499/1/012030
https://doi.org/10.1088/1755-1315/1499/1/012030
Klym, A., Blikharskyy, Y., Panchenko, O., Sobko, Y., & Blikharskyy, Z. (2024). Load-bearing capacity of the repaired RC beam using Sika MonoTop 4012. In International Scientific Conference EcoComfort and Current Issues of Civil Engineering (pp. 212-224). Springer Nature Switzerland. https://doi.org/10.1007/978-3-031-67576-8_19
https://doi.org/10.1007/978-3-031-67576-8_19
Klym, O., & Blikharskyy, Z. (2024). Determination of stress-strain state of RC beam based on DIC method. Journal of Theory and Building Practice, 2, 69-80. https://doi.org/10.23939/jtbp2024.02.069
https://doi.org/10.23939/jtbp2024.02.069
Kopiika, N., & Blikharskyy, Z. (2024). Digital image correlation for assessment of bridges' technical state and remaining resource. Structural Control and Health Monitoring, 2024, Article 1763285. https://doi.org/10.1155/2024/1763285
https://doi.org/10.1155/2024/1763285
, N., Klym, A., Blikharskyy, Y., Katunský, D., Popovych, V., & Blikharskyy, Z. (2024). Evaluation of the stress-strain state of the RC beam with the use of DIC. Production Engineering Archives, 30, 44. https://doi.org/10.30657/pea.2024.30.44
https://doi.org/10.30657/pea.2024.30.44
Lu, J., Yang, Y., Hendriks, M., & Lantsoght, E. O. L. (2025). Experiments on skewed reinforced concrete slabs failing in shear. Congress Ghent 2025, pp. 789-796. https://doi.org/10.2749/ghent.2025.0789
https://doi.org/10.2749/ghent.2025.0789
Machado, L. S., Helene, P., & Círio, M. (2023). Reliability of RC cross-sections designed for simple bending according to the 2014 and 2023 versions of NBR 6118 code. Latin American Journal of Solids and Structures, 20(4), e452. https://doi.org/10.1590/1679-78256940
https://doi.org/10.1590/1679-78256940
McCormick, N., & Lord, J. (2010). Digital image correlation. Materials Today, 13(12), 52-54. https://doi.org/10.1016/S1369-7021(10)70235-2
https://doi.org/10.1016/S1369-7021(10)70235-2
McGinnis, M., Gangone, M., Nogales Arroyo, A., Gómez-Santana, L. M., Weldon, B., Reihl, A., Tošić, N., & Kurama, Y. (2024). Experimental and numerical investigation of the bending, shear, and punching shear behavior of recycled aggregate concrete precast/prestressed hollow core slabs. Structural Concrete, 25(6), 4340-4364. https://doi.org/10.1002/suco.202400008
https://doi.org/10.1002/suco.202400008
Nguyen Van Lam, N., Nguyen Trong Khoi, N., Vu Dinh Tho, N., Dao Van Dung, D., Bui Manh Hung, B., & Khuc Anh Son, K. (2022). Model of stress-strain state of three-layered reinforced concrete structure by the finite element methods. International Journal for Computational Civil and Structural Engineering, 18(2), 62-73. https://doi.org/10.22337/2587-9618-2022-18-2-62-73
https://doi.org/10.22337/2587-9618-2022-18-2-62-73
Pan, B. (2018). Digital image correlation for surface deformation measurement: Historical developments, recent advances and future goals. Measurement Science and Technology, 29(8), 082001. https://doi.org/10.1088/1361-6501/aac55b
https://doi.org/10.1088/1361-6501/aac55b
Reu, P. L. (2011). Experimental and numerical methods for exact subpixel shifting. Experimental Mechanics, 51(4), 443-452 https://doi.org/10.1007/s11340-010-9417-4
https://doi.org/10.1007/s11340-010-9417-4
Reu, P. L., Sweatt, W., Miller, T., & Fleming, D. (2015). Camera system resolution and its influence on digital image correlation. Experimental Mechanics, 55(1), 9-25. https://doi.org/10.1007/s11340-014-9886-y
https://doi.org/10.1007/s11340-014-9886-y
Tur, V. V., Tur, O. V., & Lizahub, M. V. (2023). Experimental and theoretical study of the reinforced concrete flat slabs with the central support loss. Building and Reconstruction, 105(1), 77-103. https://doi.org/10.33979/2073-7416-2023-105-1-77-103
https://doi.org/10.33979/2073-7416-2023-105-1-77-103
Wang, G., Liu, J., Zhang, Y., Zhang, Z., Tao, J., & Wu, D. (2024). Theoretical and experimental study on the stress state of joints in two-way composite slabs. Buildings, 14(11), 3374. https://doi.org/10.3390/buildings14113374
https://doi.org/10.3390/buildings14113374
Yang, L., Shen, Q., Lu, M., & Yang, X. (2025). Experimental study on bending behaviors of ultra-high-performance fiber-reinforced concrete hollow-core slabs. Buildings, 15(5), 812. https://doi.org/10.3390/buildings15050812
https://doi.org/10.3390/buildings15050812
Zarate-Garnica, J. D., Goicolea, J. M., & Gabaldón, F. (2022). Monitoring structural responses during load testing of reinforced concrete bridges using digital image correlation. Structure and Infrastructure Engineering, 18(9), 1308-1324. https://doi.org/10.1080/15732479.2022.2063906
https://doi.org/10.1080/15732479.2022.2063906
, O., Tymoshchuk, V., Zhuravska, N., & Hajiyev, M. (2020). Influence of strengthening flat slab by external prestressed reinforcement on deformation characteristics of the slab. In Building Innovations (pp. 449-456). Springer. https://doi.org/10.1007/978-3-030-85043-2_42
https://doi.org/10.1007/978-3-030-85043-2_42